Reishi Mushroom: Benefits, Forms, Dosing, and Side Effects

Reishi (Ganoderma lucidum) is an edible mushroom with a long history of use in traditional Chinese medicine, where it has been valued for purported benefits including increasing vitality and strengthening the heart. In the United States, reishi supplements are most commonly promoted for immune system support, blood sugar management, cardiovascular function, liver protection, and anti-tumor activity [1][2].

Reishi mushrooms contain approximately 400 biologically active compounds, with polysaccharides (particularly 1,3-beta-D-glucan) and triterpenes (particularly ganoderic acids) being the most pharmacologically significant. Beta-glucans are thought to be responsible for many of reishi's potential immune-modulating and anti-inflammatory effects, while ganoderic acids have demonstrated anticancer, antiviral, antioxidant, and antiplatelet aggregation activity in preclinical studies. However, it is critical to note that many of these findings come from cell culture and animal models, and the translation to clinical benefit in humans remains incomplete for most proposed uses.

Table of Contents

• Overview
• Forms and Bioavailability
• Evidence for Benefits
• Recommended Dosing
• Safety and Side Effects
• Drug Interactions
• Dietary Sources
• References

Overview

Reishi (Ganoderma lucidum) is an edible mushroom with a long history of use in traditional Chinese medicine, where it has been valued for purported benefits including increasing vitality and strengthening the heart. In the United States, reishi supplements are most commonly promoted for immune system support, blood sugar management, cardiovascular function, liver protection, and anti-tumor activity [1][2].

The reishi mushroom consists of several distinct anatomical parts. The fruiting body (also called the mushroom or fruitbody) is the most visible portion and contains spores on its underside. Once released, spores land and — under proper conditions — form thread-like structures called hyphae, which develop into a branching network known as the mycelium. The mycelium in turn gives rise to a new fruiting body, completing the reproductive cycle. Most reishi supplements are made from the dried fruiting body, with or without mycelium; some products contain mycelium alone [1].

Reishi mushrooms contain approximately 400 biologically active compounds [3]. The two most pharmacologically significant classes are:

• Polysaccharides, particularly 1,3-beta-D-glucan, a specific type of beta-glucan. Beta-glucans are complex carbohydrates composed of sugar molecules and are thought to be responsible for many of reishi's potential immune-modulating and anti-inflammatory effects [1][3].
• Triterpenes, particularly the ganoderic acids. These have demonstrated anticancer, antiviral, antioxidant, antiplatelet aggregation, histamine release inhibition, and cholesterol synthesis inhibition activity in preclinical studies [4].

Both the fruiting body and mycelia contain beta-glucans and ganoderic acids, although the specific sets of ganoderic acids differ between these two parts of the organism [1].

Laboratory and animal studies have found that beta-glucans from reishi mushroom possess anti-inflammatory, anti-tumor, immune-stimulating, antibacterial, antiviral, and blood-sugar-lowering effects [5][6][7][8]. Laboratory and animal studies have also found that ganoderic acids demonstrate anticancer, antiviral, antioxidant, and antiplatelet aggregation activity, and may inhibit histamine release and cholesterol synthesis [4]. However, it is critical to note that many of these findings come from cell culture and animal models, and the translation to clinical benefit in humans remains incomplete for most proposed uses.

Forms and Bioavailability

Types of Reishi Products

Reishi supplements are available in several forms, each with distinct compositional profiles:

Dried Mushroom Powder: Ground whole fruiting body, sometimes including mycelium. Contains the full spectrum of compounds (beta-glucans, ganoderic acids, other polysaccharides, proteins, fiber) but at lower concentrations than extracts. Typical doses in clinical trials using powder range from 1,500 mg to 6,000 mg per day [1][9].

Powdered Extracts: Concentrated forms typically made using hot water extraction, alcohol extraction, or dual extraction (both). Extracts have higher concentrations of target compounds such as beta-glucans and ganoderic acids. Water-soluble extracts are enriched in polysaccharides (beta-glucans), while alcohol-based extracts capture more triterpenes (ganoderic acids). Some products are standardized to a specific percentage of polysaccharides or beta-glucans — for example, the Ganopoly extract used in several clinical trials was standardized to 25% polysaccharides [10][11].

Spore Products: Reishi spores contain bioactive compounds but have a hard outer shell (sporoderm) that may limit absorption. Some manufacturers offer "cracked" or "broken-wall" spore products to improve bioavailability. At least one clinical trial used a combined formula of mushroom extract plus spores [12].

Mushroom Blends/Complexes: Many products combine reishi with other medicinal mushrooms such as maitake (Grifola frondosa), shiitake (Lentinula edodes), lion's mane (Hericium erinaceus), and cordyceps (Cordyceps sinensis). While blends may offer a broader range of bioactive compounds, they make it difficult to attribute effects to any single mushroom species [1][13].

Fruiting Body vs. Mycelium

This is an important distinction that affects product quality:

• Fruiting body products contain the mushroom itself and tend to have higher concentrations of beta-glucans and ganoderic acids [1].
• Mycelium products are grown on grain substrates (typically rice or oats), and components of these grains will be present in the final product. Products labeled "mycelial biomass" or "mycelium biomass" may contain significant amounts of grain-derived starch and alpha-glucans rather than the bioactive 1,3-beta-D-glucan from the mushroom [1].
• When mycelia is listed before fruiting body in the Supplement Facts panel, this indicates the product contains more mycelia than fruiting body [1].
• If a product label lists only "polysaccharides" rather than specifying 1,3-beta-D-glucan, the polysaccharide content may be predominantly alpha-glucan or cellulose derived from the grain substrate rather than the bioactive mushroom beta-glucans [1].

Absorption Considerations

Evidence on the optimal timing of reishi supplementation relative to meals is mixed. Some product labels advise taking reishi with food, while others state it can be taken with or without food. A small preliminary study in humans found that consuming reishi extracts with food may actually inhibit the absorption of certain ganoderic acids [14]. This suggests that for maximal triterpene absorption, taking reishi on an empty stomach may be preferable, although more research is needed to confirm this finding.

Comparison of Reishi Product Types

Product Type	Key Compounds	Typical Daily Dose	Notes
Dried mushroom powder	Beta-glucans, ganoderic acids (lower concentration)	1,500-6,000 mg	Full-spectrum but less concentrated
Water extract	Polysaccharides (beta-glucans)	1,500-5,400 mg	Enriched in water-soluble compounds; used in most clinical trials
Alcohol/dual extract	Triterpenes (ganoderic acids) + polysaccharides	Varies by standardization	Better triterpene extraction
Spore powder	Bioactive oils, triterpenes	500-1,000 mg	Hard shell may limit absorption; "cracked" spores may be more bioavailable
Mushroom blends	Varies by species composition	Varies	Cannot attribute effects to reishi specifically

Evidence for Benefits

Immune Function and Cancer

Reishi has been most extensively studied for its effects on immune function, particularly in the context of cancer. The evidence base ranges from laboratory studies to small clinical trials.

Cochrane Review of Clinical Trials: A systematic review of five clinical trials concluded that reishi mushroom might help to stimulate immune function when taken in addition to conventional anti-cancer treatment, but noted that long-term studies are needed before recommending reishi as a first-line therapy [15]. This review provides the broadest assessment of reishi's role in oncology and highlights that the evidence, while suggestive, remains preliminary.

Immune Function in Advanced Cancer (Uncontrolled): A small study examined the effects of 1,800 mg of a reishi mushroom extract (Ganopoly, standardized to 25% polysaccharides) taken three times daily with meals (total daily dose 5,400 mg) for three months in people with various advanced-stage cancers (lung, breast, liver, colon, prostate, bladder, and brain) who were not receiving other treatments. The extract significantly increased several measures of immune function — natural killer (NK) cell activity, interleukin-2 (IL-2), interleukin-6 (IL-6), and interferon (IFN) — and significantly decreased tumor necrosis factor (TNF). However, this study did not include a control group, nor did it determine whether the treatment had any effect on reducing or eliminating tumors [10]. Both limitations substantially weaken the conclusions that can be drawn.

Lung Cancer (Placebo-Controlled): In a placebo-controlled trial, people with lung cancer who received 1,800 mg of Ganopoly daily for three months had a significant increase in natural killer cell activity, while NK cell activity remained unchanged in those who received placebo [11]. Measures of tumor change were not reported, although 65% of those receiving the extract reported improvement in their quality of life compared to 14% of placebo recipients. Both this and the preceding study were funded by the manufacturer of the extract, which introduces potential bias.

Colorectal Adenomas: A study in 198 men and women with colorectal adenomas (non-cancerous lesions that can become cancerous) examined the effects of 1,500 mg per day of a water-soluble reishi mushroom extract for one year. Participants receiving reishi showed a slight average decrease in adenoma size (1.4 mm) and number (0.42 fewer) compared to untreated controls, who experienced slight average increases in size (1.73 mm) and number (0.66 more) [16]. While statistically significant, the clinical relevance of these modest changes is uncertain.

Prostate Cancer (Preliminary): Laboratory and animal studies suggest that certain ganoderic acids in reishi may inhibit 5-alpha-reductase and the conversion of testosterone into dihydrotestosterone (DHT), and may inhibit the growth of certain types of prostate cancer cells [17]. However, human evidence is very limited. One small, unblinded, non-placebo-controlled study in Japan among men with non-metastasized prostate cancer who had experienced a biochemical recurrence after treatment (surgery, radiation, etc.) found that reishi supplementation for 6 months did not affect levels of PSA or testosterone. Side effects were mild and included skin rash, upset stomach, heartburn, and changes in hemoglobin levels [18].

Tumor Marker Concern: In a concerning case series, five people with gastrointestinal cancer experienced increases in the tumor marker CA72-4 while taking a reishi mushroom spore supplement. Levels of the marker rapidly returned to normal when patients discontinued the supplement, and no change in clinical symptoms accompanied the CA72-4 surge [19]. While the clinical significance is unclear, this finding warrants caution in cancer patients using tumor markers for disease monitoring.

Context from Other Mushroom-Derived Compounds: Drugs developed from the polysaccharides of other mushrooms have been used in countries such as China and Japan to help enhance the effects of chemotherapy drugs [20]. For example, Lentinan, which contains 1,3-beta-D-glucan derived from shiitake mushroom, when given intravenously in addition to chemotherapy, has been shown to help improve survival rates in people with certain types of liver and gastric cancers [21][22]. However, it is not clear whether 1,3-beta-glucan taken as an oral supplement would produce the same effects as intravenous administration.

Preclinical Evidence Summary: In laboratory settings, beta-glucans from reishi have demonstrated anti-inflammatory, anti-tumor, and immune-stimulating effects [5][6], while ganoderic acids have shown anticancer activity across multiple cancer cell lines [4]. These findings provide mechanistic rationale for clinical investigation but cannot be directly extrapolated to supplement use in humans.

Diabetes and Blood Sugar

The evidence on reishi for diabetes and blood sugar control is mixed, with some early positive findings contradicted by later, more rigorous studies.

HbA1c Reduction (Early Positive Trial): A study in 71 people with type 2 diabetes found that reishi mushroom extract (Ganopoly) taken three times daily with meals (total daily dose 5,400 mg) for three months reduced hemoglobin A1C (HbA1c) — a measure of long-term blood sugar control — compared to placebo. However, fasting glucose levels were not significantly affected [23].

Cochrane Review (Negative Overall Conclusion): A subsequent Cochrane review of five clinical trials, including the 2004 trial above, determined that reishi's effects on blood glucose were unclear and that the evidence did not support its use for treating cardiovascular risk factors in people with type 2 diabetes mellitus [24].

Type 2 Diabetes with Metabolic Syndrome (Negative): A 16-week study among 75 men and women in Australia with type 2 diabetes and metabolic syndrome found that neither reishi taken alone (3,000 mg daily of a formula containing 2,240 mg of a 10:1 mushroom extract plus 740 mg reishi spores) nor reishi taken in combination with Cordyceps sinensis mushroom extract reduced HbA1c, fasting glucose levels, or improved measures of cardiovascular health such as total cholesterol, LDL cholesterol, or triglycerides. Reishi also did not reduce waist circumference or body mass index (BMI) compared to placebo [12].

Oyster Mushroom and Beta-Glucans for Blood Sugar (Negative): A study in Germany among 22 men and women with pre-diabetes (impaired glucose tolerance) who were not taking blood-sugar-lowering medication found that 20 grams of oyster mushroom (Pleurotus ostreatus) powder containing 8.1 grams of total beta-glucans added to a single carbohydrate-rich meal did not minimize the increase in blood sugar or triglycerides, improve insulin response, or affect blood levels of ghrelin over a four-hour period compared to the same meal without mushroom powder. However, it did modestly increase blood levels of glucagon-like peptide-1 (GLP-1) by 17%. Self-reported hunger was reduced by 22%, but there were no changes in satiety, fullness, or desire to eat. The authors noted that because beta-glucans in mushrooms are partly cross-linked with chitin, their water-solubility and thus efficacy might be lower compared to cereal beta-glucans [25]. While this study used oyster mushroom rather than reishi, the findings are relevant because they speak to the bioavailability limitations of mushroom-derived beta-glucans more broadly.

Overall Assessment: The early positive trial showing HbA1c reduction has not been consistently replicated in later, better-designed studies. The Cochrane review and the Australian RCT both found no meaningful benefit. The evidence does not currently support the use of reishi for blood sugar management or diabetes treatment.

Liver Health

Reishi has traditionally been used for liver protection, and there is limited clinical evidence along with some preclinical support for this use. However, this area is complicated by reports of reishi itself causing liver damage in some individuals.

Preclinical Evidence: Animal studies suggest reishi may help protect the liver from alcohol-induced and chemically-induced liver damage, as well as cirrhosis due to biliary dysfunction [26][27][28]. Reishi has also been reported to speed the healing time of gastric ulcers in rats [29].

Fatty Liver (Clinical Trial): A study among 39 men and women in China aged 40 to 54 with mildly fatty livers who were otherwise healthy found that supplementation with a triterpenoid- and polysaccharide-enriched reishi formula for six months reduced measures of oxidative stress and decreased liver enzymes associated with liver damage: glutamic-oxaloacetic transaminase (GOT) fell by 42% and glutamic-pyruvic transaminase (GPT) fell by 27% compared to pre-supplementation values. Supplementation also appeared to reduce fatty liver conditions when examined by ultrasound. One capsule containing 225 mg of reishi providing 7% triterpenoid-ganoderic acids and 6% polysaccharide peptides was taken once daily after a meal [30].

Important Caveat: Despite these protective findings, there have been three documented cases of liver damage in people taking powdered reishi mushroom, including one fatal case (see Safety and Side Effects section). This apparent contradiction — liver protection in some contexts and liver injury in others — is not fully understood and underscores the importance of monitoring liver function during reishi use [31][32][33].

Fibromyalgia

A single clinical trial has examined reishi for fibromyalgia. A study in Brazil among 48 women with fibromyalgia (average age 55) found that supplementation with 3,000 mg of reishi powder dissolved in warm water twice daily (total daily dose 6,000 mg) for six weeks modestly improved some measures of physical fitness, including aerobic endurance, lower body flexibility, and walking speed, compared to supplementation with Ceratonia siliqua (carob — used as an active control due to its antioxidant properties). Notably, the percentage of beta-glucans in the reishi powder was not specified, and effects on the core symptoms of fibromyalgia — muscle pain, stiffness, and tenderness — were not measured [9]. This single study provides very preliminary evidence and cannot establish reishi as a treatment for fibromyalgia.

Gut Microbiota and Butyrate Production

Beta-glucans found in mushrooms, including reishi, are known to promote butyrate-producing bacteria in the colon [34][35]. Butyrate is a short-chain fatty acid produced primarily by the fermentation of undigested carbohydrates in the gut. It has anti-inflammatory effects, may help strengthen gut barrier function, and may play a role in modulating the immune system and metabolism.

In Vitro Evidence: A freeze-dried mushroom powder blend of reishi, maitake, and oyster mushrooms (Ganoderma lucidum, Grifola frondosa, and Pleurotus ostreatus) was found in a laboratory study to increase the number of butyrate-producing bacteria and correspondingly increase butyrate production over three days when applied daily (500 mg, 1,000 mg, or 1,500 mg per day) to cultures of human gut bacteria in a dose-dependent manner, compared to a control medium not exposed to the mushroom blend [36].

Limitations: This study was conducted in vitro (in a laboratory setting with cultured bacteria), not in living humans. Trials in people are needed to determine if these effects occur after oral ingestion of mushroom beta-glucans and what clinical benefits, if any, are associated with the observed increases in butyrate production.

Anti-Inflammatory and Antioxidant Activity

Reishi's anti-inflammatory and antioxidant properties have been extensively characterized in preclinical models. Beta-glucans modulate immune cell activity, including macrophage activation, cytokine production, and natural killer cell function [5][6]. Ganoderic acids have demonstrated antioxidant effects and may reduce oxidative stress markers [4]. The fatty liver trial described above found reduced markers of oxidative stress in participants taking a triterpenoid-enriched reishi formula [30].

However, it is important to distinguish between preclinical findings (cell and animal studies) and clinical evidence. No large, well-designed clinical trial has specifically evaluated reishi as an anti-inflammatory or antioxidant intervention in humans. The immune-modulating effects observed in cancer trials provide the most direct human evidence for reishi's effects on inflammatory and immune pathways.

Cardiovascular Health

Preclinical studies suggest that ganoderic acids from reishi may inhibit cholesterol synthesis [4] and have antiplatelet aggregation effects [4]. The Cochrane review of reishi in diabetes found no evidence for cardiovascular benefit (improvement in LDL cholesterol, total cholesterol, or triglycerides) in people with type 2 diabetes [24]. The Australian RCT similarly found no cardiovascular improvements [12]. Currently, there is insufficient evidence to recommend reishi for cardiovascular health in humans.

Antiviral and Antibacterial Activity

Laboratory studies have reported antiviral and antibacterial effects of reishi compounds [7][4]. Beta-glucans have demonstrated antiviral activity in cell culture models, and ganoderic acids have shown antiviral effects in preclinical settings. However, no clinical trials have evaluated reishi's antiviral or antibacterial effects in humans. These remain preclinical observations without established clinical relevance.

Recommended Dosing

There is no established standard dose for reishi mushroom supplementation. Doses used in clinical trials have varied widely depending on the form of the product and the condition being studied.

Doses Used in Clinical Trials

Condition	Form	Daily Dose	Duration	Reference
Immune function in advanced cancer	Ganopoly extract (25% polysaccharides)	5,400 mg (1,800 mg x 3)	3 months	[10]
Lung cancer (immune support)	Ganopoly extract	1,800 mg	3 months	[11]
Colorectal adenomas	Water-soluble extract	1,500 mg	12 months	[16]
Type 2 diabetes (HbA1c)	Ganopoly extract	5,400 mg (1,800 mg x 3)	3 months	[23]
Type 2 diabetes + metabolic syndrome	10:1 extract + spores	3,000 mg	16 weeks	[12]
Fibromyalgia	Mushroom powder	6,000 mg (3,000 mg x 2)	6 weeks	[9]
Fatty liver	Enriched formula (7% ganoderic acids, 6% polysaccharides)	225 mg	6 months	[30]

General Dosing Guidance

Powdered reishi mushroom (non-extract): 1,500-9,000 mg per day, typically divided into 2-3 doses [1].

Standardized extract (e.g., standardized to polysaccharide content): 1,500-5,400 mg per day, divided into 2-3 doses taken with meals. The most common dose in clinical trials using the Ganopoly extract was 1,800 mg three times daily (5,400 mg total) [10][11][23].

Concentrated extracts (e.g., 10:1): Lower absolute doses due to concentration factor. The Australian diabetes trial used 2,240 mg of a 10:1 extract plus 740 mg spores (total 3,000 mg) [12].

Enriched/specialized formulas: Much lower doses may be used when the product is concentrated in specific active compounds. The fatty liver trial used only 225 mg per day of a formula enriched in triterpenoids and polysaccharides [30].

Important Dosing Considerations

• No official Recommended Dietary Allowance (RDA), Adequate Intake (AI), or Tolerable Upper Intake Level (UL) has been established for reishi.
• Most clinical trials used reishi with meals, but limited evidence suggests that food may inhibit the absorption of certain ganoderic acids (triterpenes) [14]. The clinical significance of this finding is unclear.
• Beta-glucan content varies enormously between products. A product standardized to 25% polysaccharides delivers a very different amount of bioactive compounds than unextracted mushroom powder at the same weight.
• Higher doses (5,400 mg per day of Ganopoly extract) were generally well tolerated in clinical trials lasting up to 3 months [10][11][23]. Long-term safety data at high doses is limited.
• Some clinical evidence suggests that high doses (3,000 mg per day of reishi mushroom powder) may have a blood-thinning effect, while lower doses (1,500 mg per day) may not [37][38].

Safety and Side Effects

Common Side Effects

In clinical studies, the following mild side effects have been reported with reishi supplementation [1][37]:

• Skin rash
• Itchiness
• Nausea
• Heartburn
• Upset stomach
• Insomnia

These side effects were generally considered mild and were not dose-limiting in the trials where they were reported.

Blood-Thinning Effects

Some clinical evidence suggests that reishi may have anticoagulant properties at higher doses. A study found that doses of 3,000 mg per day had a blood-thinning effect, while lower doses (1,500 mg per day) may not [37][38]. Ganoderic acids have demonstrated antiplatelet aggregation effects in laboratory studies [4]. People taking anticoagulant or antiplatelet medications, or those preparing for surgery, should exercise caution and consult their healthcare provider before using reishi supplements.

Liver Toxicity

Three cases of liver damage have been documented in people taking powdered reishi mushroom:

Case 1 (China, fatal): A case of liver damage associated with powdered reishi mushroom use was reported in China. The outcome was fatal [31].

Case 2 (Thailand): A second case of liver injury was reported in Thailand associated with reishi powder use [32].

Case 3 (Japan): A 61-year-old man in Japan who, several months after beginning reishi supplementation, developed elevated liver enzymes, an extremely elevated white blood cell count (eosinophilia), and liver nodules (which developed as a result of the very high white blood cell counts), along with symptoms including nausea, fever, and fatigue. His symptoms improved several weeks after discontinuing the supplement, and within three months liver enzyme levels and white blood cell counts returned to normal ranges and liver nodules resolved. Notably, he had a prior history of liver injury with certain other medications, suggesting that some individuals may be more susceptible to this type of hepatotoxic reaction [33].

The mechanism behind reishi-associated liver injury is not well understood. Given that one case was fatal, individuals with pre-existing liver disease or a history of drug-induced liver injury should exercise particular caution with reishi supplementation.

HMGCR Immune-Mediated Necrotizing Myopathy (HMGCR IMNM)

People with a history of muscle breakdown due to the autoimmune condition known as HMGCR IMNM (HMG-CoA reductase immune-mediated necrotizing myopathy) should avoid mushrooms and mushroom supplements, including those containing reishi, as they may worsen symptoms or trigger a flare [39][40].

HMGCR IMNM causes the body to attack muscle tissue, leading to muscle weakness and fatigue. It is most commonly triggered by statin medications, which inhibit HMG-CoA reductase (HMGCR), a key enzyme in cholesterol synthesis. However, small amounts of lovastatins or other compounds that naturally occur in reishi and other mushrooms also inhibit this enzyme and may trigger an immune response in susceptible individuals [39][40].

A documented case involved a 30-year-old woman with a history of non-statin-related HMGCR IMNM that had been previously treated. She experienced a flare after taking a mushroom complex supplement containing 200 mg reishi, 200 mg maitake, and 200 mg shiitake, as well as cordyceps. Her condition gradually worsened with progressive weakness and elevated blood levels of creatine kinase (a marker of muscle breakdown) over three months. After discontinuing the supplement, her condition improved over six months and creatine kinase levels decreased to normal ranges without any other interventions [41].

The lovastatin content of reishi is relatively low (approximately 0.01 mg/g dry weight) compared to some other mushrooms. Lion's mane contains approximately 0.2 mg/g and Cordyceps sinensis contains approximately 1.4 mg/g [42]. However, even low levels may be sufficient to trigger a flare in sensitized individuals.

Interference with Diagnostic Testing

People taking reishi or any other mushroom supplement should inform their healthcare provider if being tested for fungal infections. The 1,3-beta-D-glucan from mushroom supplements can potentially interfere with beta-glucan assays used to diagnose invasive fungal infections, potentially producing false-positive results [43].

Pregnancy and Breastfeeding

There are insufficient data on the safety of reishi supplementation during pregnancy or breastfeeding. Given the lack of safety data and the potential for immune-modulating effects, reishi supplements should be avoided during pregnancy and lactation unless specifically advised by a healthcare provider.

Drug Interactions

Anticoagulants and Antiplatelet Agents

Reishi may potentiate the effects of blood-thinning medications due to its demonstrated antiplatelet aggregation properties [4][37][38]. This interaction is supported by laboratory evidence showing that ganoderic acids inhibit platelet aggregation and by clinical evidence suggesting blood-thinning effects at doses of 3,000 mg per day. People taking warfarin, heparin, aspirin, clopidogrel, or other anticoagulant/antiplatelet medications should consult their healthcare provider before using reishi. A case report noted that a patient experienced bleeding complications potentially related to reishi use in the context of anticoagulant therapy [38].

Antihypertensive Medications

Reishi has been reported to have mild hypotensive (blood-pressure-lowering) effects. While this has not been a prominent finding in clinical trials, individuals taking antihypertensive medications should be aware of potential additive effects.

Immunosuppressant Medications

Reishi has immune-stimulating properties, particularly the upregulation of natural killer cell activity, IL-2, IL-6, and interferon [10][11]. This immune activation may theoretically counteract the effects of immunosuppressant medications used to prevent transplant rejection or treat autoimmune conditions (e.g., cyclosporine, tacrolimus, corticosteroids, azathioprine). Patients on immunosuppressive therapy should avoid reishi unless specifically advised otherwise by their physician.

Chemotherapy Drugs

The Cochrane review noted that reishi may help stimulate immune function when taken alongside conventional anti-cancer treatment [15]. However, the interaction between reishi and specific chemotherapy agents has not been well characterized. The tumor marker elevation observed in gastrointestinal cancer patients taking reishi spores [19] raises additional concerns about unpredictable interactions in the oncology setting. Cancer patients should consult their oncologist before using reishi.

Statin Medications

Reishi contains small amounts of naturally occurring lovastatin-like compounds [39][40][42]. While the lovastatin content in reishi is very low (approximately 0.01 mg/g dry weight), there is a theoretical risk of additive muscle toxicity when combined with statin medications, particularly in individuals with a history of statin-related myopathy. This interaction is primarily a concern for people with HMGCR IMNM but may be relevant for other statin-sensitive individuals.

Diabetes Medications

One clinical trial found that reishi extract reduced HbA1c [23], though later studies did not replicate this finding [12][24]. As a precautionary measure, people taking blood-sugar-lowering medications (metformin, sulfonylureas, insulin) should monitor blood glucose levels when starting reishi supplementation, as additive hypoglycemic effects are theoretically possible.

Hepatotoxic Medications

Given the documented cases of reishi-associated liver injury [31][32][33], caution is warranted when combining reishi with other potentially hepatotoxic medications. Patients taking medications known to affect the liver (acetaminophen at high doses, certain antibiotics, antifungals, anticonvulsants, or statins) should inform their healthcare provider before adding reishi supplementation.

Dietary Sources

Reishi mushroom (Ganoderma lucidum) is not a common dietary item in Western cuisines. In traditional Chinese and East Asian medicine, it has been consumed as a tea, in soups, or as a decoction (boiled extract) for centuries. The dried mushroom is extremely tough and woody, with a bitter taste, making it unsuitable for eating whole in the way that culinary mushrooms like shiitake or oyster mushrooms are consumed.

Traditional Preparations

• Reishi tea/decoction: Dried reishi slices boiled in water for 1-2 hours. This is the most traditional preparation method and primarily extracts water-soluble compounds (polysaccharides/beta-glucans).
• Soups and broths: Dried reishi added to soups during cooking. The mushroom pieces are typically removed before serving due to their tough, bitter nature.
• Tinctures: Reishi soaked in alcohol (typically rice wine in traditional preparations) to extract triterpenes, which are less water-soluble.

Beta-Glucans in Other Mushrooms

While reishi is the most commonly supplemented medicinal mushroom for immune support, beta-glucans are found in many edible mushroom species. Incorporating a variety of mushrooms into the diet provides dietary beta-glucans, though at lower concentrations than found in reishi supplements:

Mushroom	Beta-Glucan Content (approximate, dry weight)	Culinary Use
Shiitake (Lentinula edodes)	2-10%	Widely used in Asian cuisines; stir-fries, soups
Maitake (Grifola frondosa)	10-30%	"Hen of the woods"; roasted, sauteed, in soups
Oyster mushroom (Pleurotus ostreatus)	5-15%	Common culinary mushroom worldwide
King oyster (Pleurotus eryngii)	5-15%	Sliced and grilled, sauteed
Lion's mane (Hericium erinaceus)	10-25%	Shredded for "crab cake" texture, sauteed

Note: Beta-glucan content varies widely depending on growing conditions, processing methods, and measurement techniques. The beta-glucans in mushrooms are partly cross-linked with chitin, which may reduce their water-solubility and bioavailability compared to cereal beta-glucans (e.g., from oats or barley) [25].

Other Dietary Sources of Beta-Glucans

Beta-glucans are not unique to mushrooms. Oats and barley are rich in 1,3-1,4-beta-D-glucan (a slightly different structure from the 1,3-1,6-beta-D-glucan predominant in mushrooms), which has well-established evidence for cholesterol reduction and blood sugar management. Yeast (Saccharomyces cerevisiae) cell walls are another source of 1,3-1,6-beta-D-glucan structurally similar to mushroom beta-glucans [34].

References

1. ConsumerLab. "Reishi Mushroom Supplements Review." Accessed 2026. https://www.consumerlab.com/reviews/reishi-mushroom-supplements-review/reishi/

2. National Center for Complementary and Integrative Health (NCCIH). "Reishi Mushroom." https://www.nccih.nih.gov/health/reishi-mushroom

3. Loyd AL, et al. "Identifying the 'Mushroom of Immortality': Assessing the Ganoderma Species Composition in Commercial Reishi Products." Front Microbiol. 2018;9:1557. https://doi.org/10.3389/fmicb.2018.01557

4. Hsu CL, Yen GC. "Ganoderic acid and lucidenic acid (triterpenoid)." In: Enzymes. 2014;36:33-56. https://doi.org/10.1016/B978-0-12-802215-3.00003-3

5. Bao XF, et al. "Structural features of immunologically active polysaccharides from Ganoderma lucidum." Carbohydr Res. 2001;332(1):67-74. https://doi.org/10.1016/S0008-6215(01)00075-4

6. Chang ST, Wasser SP. "The role of culinary-medicinal mushrooms on human welfare with a pyramid model for human health." In Vivo. 2009;23(1):1-15. https://pubmed.ncbi.nlm.nih.gov/19368118/

7. Oh HM, et al. "Immunostimulating activity of Ganoderma lucidum." J Ethnopharmacol. 2000;69(2):175-181. https://doi.org/10.1016/S0378-8741(99)00166-5

8. Hikino H, et al. "Mechanisms of hypoglycemic activity of ganoderan B: a glycan of Ganoderma lucidum fruit bodies." Planta Med. 1985;51(4):339-340. https://doi.org/10.1055/s-2007-969507

9. Mateo J, et al. "Effects of Ganoderma lucidum on physical fitness in women with fibromyalgia." Nutr Hosp. 2015;32(5):2126-2135. https://doi.org/10.3305/nh.2015.32.5.9601

10. Gao Y, et al. "Effects of ganopoly (a Ganoderma lucidum polysaccharide extract) on the immune functions in advanced-stage cancer patients." Immunol Invest. 2003;32(3):201-215. https://doi.org/10.1081/IMM-120022979

11. Gao Y, et al. "Effects of Water-Soluble Ganoderma lucidum Polysaccharides on the Immune Functions of Patients with Advanced Lung Cancer." Int J Med Mushrooms. 2003;5(4):368-381. https://doi.org/10.1615/InterJMedicMush.v5.i4.40

12. Klupp NL, et al. "Ganoderma lucidum mushroom for the treatment of cardiovascular risk factors." Sci Rep. 2016;6:37278. https://doi.org/10.1038/srep37278

13. Adler BL, et al. "Mushroom supplement use as a potential trigger for anti-HMGCR immune-mediated necrotising myopathy." BMJ Case Rep. 2022;15:e248713. https://doi.org/10.1136/bcr-2022-248713

14. Teekachunhatean S, et al. "Pharmacokinetics of ganoderic acids A and F after oral administration of Ling Zhi preparation in healthy male volunteers." Evid Based Complement Alternat Med. 2012;2012:780892. https://doi.org/10.1155/2012/780892

15. Jin X, et al. "Ganoderma lucidum (Reishi mushroom) for cancer treatment." Cochrane Database Syst Rev. 2012;(6):CD007731. https://doi.org/10.1002/14651858.CD007731.pub2

16. Oka S, et al. "A water-soluble extract from culture medium of Ganoderma lucidum mycelia suppresses the development of colorectal adenomas." Hiroshima J Med Sci. 2010;59(1):1-6. https://pubmed.ncbi.nlm.nih.gov/20518254/

17. Johnson BM, et al. "Mechanistic evaluation of the anti-androgenic effects of Ganoderma lucidum in prostate cancer cells." Open Prost Cancer J. 2010;3:1-12.

18. Yoshimura K, et al. "A pilot study of reishi mushroom extract in men with biochemically recurrent prostate cancer." Int J Urol. 2010;17(6):548-556. https://doi.org/10.1111/j.1442-2042.2010.02514.x

19. Yan B, et al. "Mushroom-Derived Supplements Can Trigger Elevation of CA72-4 in Patients with Gastrointestinal Cancer." Integr Cancer Ther. 2014;13(6):NP26-NP29. https://doi.org/10.1177/1534735414525688

20. Ooi VE, Liu F. "Immunomodulation and anti-cancer activity of polysaccharide-protein complexes." Curr Med Chem. 2000;7(7):715-729. https://doi.org/10.2174/0929867003374705

21. Yang P, et al. "Lentinan as an immunotherapeutic for treating lung cancer: a review of 12 years clinical studies in China." Adv Ther. 2008;25(4):406-414.

22. Oba K, et al. "Individual patient based meta-analysis of lentinan for unresectable/recurrent gastric cancer." Anticancer Res. 2009;29(7):2739-2745. https://pubmed.ncbi.nlm.nih.gov/19596954/

23. Gao Y, et al. "A phase I/II study of Ling Zhi mushroom Ganoderma lucidum extract in patients with type II diabetes mellitus." Int J Med Mushrooms. 2004;6(1):33-40. https://doi.org/10.1615/IntJMedMushr.v6.i1.30

24. Klupp NL, et al. "Ganoderma lucidum mushroom for the treatment of cardiovascular risk factors." Cochrane Database Syst Rev. 2015;(2):CD007259. https://doi.org/10.1002/14651858.CD007259.pub2

25. Dicks L, et al. "Effects of a single dose of Pleurotus ostreatus on postprandial blood glucose, insulin, lipids, and appetite." Eur J Nutr. 2021;60(8):4397-4408. https://doi.org/10.1007/s00394-021-02590-w

26. Lakshmi B, et al. "Antiperoxidative, anti-inflammatory and antimutagenic activities of ethanol extract of the mycelium of Ganoderma lucidum." J Ethnopharmacol. 2006;107(3):297-303. https://doi.org/10.1016/j.jep.2006.01.011

27. Shieh YH, et al. "Evaluation of the hepatic and renal-protective effects of Ganoderma lucidum in mice." Am J Chin Med. 2001;29(1):1-13. https://doi.org/10.1142/S0192415X01000022

28. Park EJ, et al. "Antihepatotoxic activity of Ganoderma lucidum in galactosamine-induced liver injury in rats." Biol Pharm Bull. 1997;20(12):1234-1237. https://doi.org/10.1248/bpb.20.1234

29. Gao Y, et al. "Antiulcer activity of Ganoderma lucidum polysaccharides in rats." J Med Food. 2004;7(4):417-421. https://doi.org/10.1089/jmf.2004.7.417

30. Chiu HF, et al. "Triterpenoids and polysaccharide peptides-enriched Ganoderma lucidum: a randomized, double-blind placebo-controlled crossover study of its effects on markers of antioxidative status and fatty liver." Pharm Biol. 2017;55(1):1024-1033. https://doi.org/10.1080/13880209.2017.1279672

31. Yuen MF, et al. "Hepatotoxicity due to a formulation of Ganoderma lucidum (lingzhi)." J Hepatol. 2004;41(4):686-687. https://doi.org/10.1016/j.jhep.2004.06.016

32. Wanmuang H, et al. "Fatal fulminant hepatitis associated with Ganoderma lucidum (Lingzhi) mushroom powder." J Med Assoc Thai. 2007;90(1):179-181. https://pubmed.ncbi.nlm.nih.gov/17621752/

33. Kogure T, et al. "A case of drug-induced liver injury and eosinophilia associated with reishi mushroom supplementation." Intern Med. 2021;60(22):3625-3629. https://doi.org/10.2169/internalmedicine.7615-21

34. Friedman M. "Mushroom Polysaccharides: Chemistry and Antiobesity, Antidiabetes, Anticancer, and Antibiotic Properties in Cells, Rodents, and Humans." Foods. 2016;5(4):80. https://doi.org/10.3390/foods5040080

35. Han B, et al. "Dietary Beta-Glucans as a Stimulant of Gut Immunity." Front Immunol. 2020;11:1557. https://doi.org/10.3389/fimmu.2020.01557

36. Verhoeven J, et al. "A blend of 3 mushrooms dose-dependently increases butyrate production by human gut microbiota ex vivo." Benef Microbes. 2021;12(6):601-612. https://doi.org/10.3920/BM2021.0015

37. Tao J, Feng KY. "Experimental and clinical studies on inhibitory effect of Ganoderma lucidum on platelet aggregation." J Tongi Med Univ. 1990;10(4):240-243.

38. Kwok Y, et al. "A potential association of bleeding complications with herbal supplements: a case report." Anesth Analg. 2005;100(4):1187-1189. https://doi.org/10.1213/01.ANE.0000148123.34154.78

39. Berger A, et al. "Cholesterol-lowering properties of Ganoderma lucidum in vitro, ex vivo, and in hamsters and minipigs." Lipids Health Dis. 2004;3:2. https://doi.org/10.1186/1476-511X-3-2

40. Gil-Ramirez A, et al. "Screening of the HMG-CoA reductase inhibitory activity of several edible mushrooms." International Conference on Mushroom Biology and Mushroom Biotechnology Products (ICMBBP). 2011.

41. Adler BL, et al. "Mushroom supplement use as a potential trigger for anti-HMGCR immune-mediated necrotising myopathy." BMJ Case Rep. 2022;15:e248713. https://doi.org/10.1136/bcr-2022-248713

42. Chen SY, et al. "Determination of lovastatin in oyster mushroom (Pleurotus ostreatus) and other mushrooms using HPLC." LWT. 2012;47(2):458-462. https://doi.org/10.1016/j.lwt.2012.02.004

43. Vu-Ticar A. "False-Positive 1,3-Beta-D-Glucan Testing: Distinguishing Supplement-Related Elevations from True Fungal Infections." Hospitalist. 2022.