Cinnamon: Benefits, Forms, Dosing, and Side Effects

Table of Contents

• Current evidence position
• Key safety points
• Brad's videos on this topic
• Overview
• Forms and Bioavailability
• Evidence for Benefits
• Recommended Dosing
• Safety and Side Effects
• Drug Interactions
• Dietary Sources
• References

Current evidence position

Brad has not made a video on this topic; this is a summary of the evidence, not his view. The US National Center for Complementary and Integrative Health (NCCIH) says research does not clearly support cinnamon for any health condition, and it is unclear whether it helps diabetes or weight loss ^[68]. A 2025 meta-analysis of 28 trials in 3,054 people with type 2 diabetes found lower fasting glucose and HbA1c with cinnamon, but results varied widely between trials ^[67]. Cassia cinnamon, the type sold most in North America, can contain a lot of coumarin, which can harm the liver in susceptible people, while Ceylon cinnamon has little or none ^{[10, 19, 68]}. Anyone who takes a blood thinner, a statin or other medicines, has liver disease or is pregnant should talk to their doctor before taking cinnamon supplements ^{[9, 53, 68]}.

Brad's videos on this topic

None yet.

1. Overview

Cinnamon is a spice made from the dried bark of several species of Cinnamomum trees ^[68]. Its bark, leaves, flowers, fruits and roots have a long history of use in traditional medicine and cooking in China, India and Persia (Iran) ^[68]. Today it is sold as a dietary supplement, mainly for diabetes and weight loss ^[68].

There are two broad categories of cinnamon available commercially:

Cassia cinnamon (Cinnamomum aromaticum, also called C. cassia) grows in southeastern Asia and is the type sold most in North America ^[68]. The four major species are C. verum (Ceylon), C. aromaticum (C. cassia), C. burmannii and C. loureiroi, and they differ in chemical make-up ^[4]. In a Czech survey, 60 samples of ground cinnamon from twelve brands came from cassia and had mean coumarin levels of 2,650 to 7,017 mg per kg ^[19]. Coumarin can harm the liver ^[10].

Ceylon cinnamon (Cinnamomum verum, also called C. zeylanicum), known as "true" cinnamon, grows mainly in Sri Lanka ^[68]. It may contain a trace of coumarin; a sample straight from a Sri Lankan plantation contained none ^{[19, 68]}.

The primary bioactive compounds in cinnamon include:

• Proanthocyanidins (PACs): water-soluble polyphenol polymers. In the laboratory, A-type PACs from cinnamon raised insulin-dependent glucose metabolism roughly 20-fold ^[6]. Cinnamon may also block the enzymes that digest starch, as the drug acarbose does ^[12].
• Cinnamaldehyde: a major compound in the bark. Trans-cinnamaldehyde made up more than 60% of the compounds found in one batch of Ceylon bark ^[11]. In laboratory tests it is active against Candida yeasts ^[44].
• Coumarin: a compound with hepatotoxic and carcinogenic properties in toxicology studies ^[10]. It is a different compound from the blood thinner warfarin, which is a coumarin derivative. The authors of one case report suggest coumarin may block vitamin K recycling, which the body needs to activate several clotting factors ^[52].

Many products do not clearly state which species or plant part they contain, and these differences change a product's chemistry and its effects on people ^[68]. That also makes many cinnamon studies hard to interpret ^[68].

2. Forms and Bioavailability

Cinnamon supplements come in several forms, which differ in what they contain.

Ground Bark Powder

The simplest form: ground bark sold loose or in capsules. Diabetes trials that gave cinnamon itself, not an extract, used 1 to 6 g a day ^{[20, 22, 23]}. The lowest dose in pooled trials, 120 mg a day, was a cinnamon extract ^{[21, 30]}.

In a crossover trial in 19 people with type 2 diabetes, 3 or 6 g of raw cinnamon stirred into water before a meal reduced the glucose spike after that meal ^[12]. The same doses taken in hard gelatin capsules lost most or all of this effect ^[12]. The trial measured glucose for only 2 hours ^[12], and capsule trials over months have also found glucose benefits ^[67].

Water-Soluble Extracts

These extracts are made by soaking cinnamon bark in water. Germany's Federal Institute for Risk Assessment has suggested water extracts of cassia, or Ceylon cinnamon, as ways to lower coumarin intake ^[29]. Two branded extracts have been tested in trials:

Cinnulin PF: a water-soluble cinnamon extract. At 500 mg a day for 12 weeks in people with prediabetes and the metabolic syndrome, it lowered fasting glucose and systolic blood pressure ^[13].

CinSulin: a spray-dried water extract of Cinnamomum cassia, tested at 250 mg twice a day for two months in people with raised blood glucose ^[14].

Cinnamon Oil

Cinnamon oil is distilled from the bark. In laboratory tests it killed Staphylococcus epidermidis bacteria and broke up their biofilms ^[42]. A woman with type 2 diabetes had a severe flare of rosacea two weeks after starting cinnamon oil pills to lower her blood sugar ^[55]. Cinnamon oil or powder on the skin may cause irritation or contact dermatitis ^[68]. None of the blood sugar trials described here tested cinnamon oil.

Cinnamon Sticks

Cinnamon sticks are rolled pieces of dried bark, usually steeped in drinks. Ceylon bark is the lower-coumarin choice for regular use ^[19].

Comparison of Cinnamon Species

Sources: ^{[4, 19, 68]}

Form Selection Guidance

• For blood sugar support: in the 2025 meta-analysis, cinnamon in capsule form lowered fasting glucose and HbA1c ^[67]. Water extracts of cassia may carry less coumarin than cassia powder ^[29].
• For regular daily use: Ceylon cinnamon has much less coumarin than cassia ^{[19, 29]}.
• Around a meal: ground cinnamon stirred into water before eating blunted the glucose spike in one trial, while capsules did not ^[12].
• Cinnamon oil: not tested for blood sugar in the trials described here.

3. Evidence for Benefits

Blood Sugar Control in Type 2 Diabetes

The evidence for cinnamon in type 2 diabetes is mixed. Several trials show benefit and others show none. Species, dose, form, length of treatment and the patients' other medicines differ from trial to trial.

Positive Trials

Khan et al. (2003): 60 adults with type 2 diabetes (mean age 52.2 years) took 1, 3 or 6 g of cinnamon a day or placebo for 40 days ^[20]. All three doses cut fasting glucose (18-29%), triglycerides (23-30%), LDL cholesterol (7-27%) and total cholesterol (12-26%), with no significant change on placebo ^[20]. In 2025 the journal issued an expression of concern about this trial, citing baseline differences between groups, unclear randomisation and unusually high adherence, so its results should be read with caution ^[69].

Lu et al. (2012): 66 Chinese patients with type 2 diabetes, all taking gliclazide, took 120 mg or 360 mg a day of cinnamon extract or placebo for 3 months ^[21]. HbA1c and fasting glucose fell in both cinnamon groups and did not change on placebo ^[21]. Triglycerides fell only in the low-dose group; total, HDL and LDL cholesterol and liver enzymes did not change ^[21].

Akilen et al. (2010): 58 UK patients with type 2 diabetes on glucose-lowering tablets and an HbA1c above 7% took 2 g of cinnamon or placebo daily for 12 weeks ^[22]. HbA1c fell from 8.22% to 7.86% with cinnamon and rose from 8.55% to 8.68% on placebo ^[22]. Fasting glucose fell from baseline with cinnamon, but not significantly compared with placebo; blood pressure findings are under Blood Pressure below ^[22].

Crawford (2009): 109 patients with type 2 diabetes and an HbA1c above 7.0 received usual care alone or usual care plus 1 g of cinnamon a day for 90 days ^[23]. HbA1c fell 0.83% (95% CI, 0.46-1.20) with cinnamon and 0.37% (95% CI, 0.15-0.59) with usual care alone ^[23].

Mandal et al. (2023): 154 patients with type 2 diabetes in northern India took 1.5 g a day of Ceylon (C. zeylanicum) bark or placebo capsules on an empty stomach for 120 days, alongside their usual treatment ^[11]. The abstract reports a change in fasting glucose of -35.50% with cinnamon versus 5.00% with placebo, and in HbA1c of -0.85% versus 0.15%, with confidence intervals that cross zero ^[11]. It is one of few trials of Ceylon rather than cassia cinnamon.

Negative Trials

Vanschoonbeek et al. (2006): 25 postmenopausal women with type 2 diabetes took Cinnamomum cassia 1.5 g/d or placebo for 6 weeks ^[24]. Cinnamon did not improve insulin sensitivity, oral glucose tolerance or blood lipids ^[24].

Wainstein et al. (2011): 59 adults with type 2 diabetes took 1,200 mg/day of cinnamon or placebo for 12 weeks ^[26]. Systolic blood pressure fell 3.4 mm Hg with cinnamon and rose 1.9 mm Hg with placebo (P=.06), but the difference disappeared after adjusting for baseline blood pressure, and the authors put it down to regression to the mean ^[26].

Acute Blood Sugar Response

Solomon et al. (2007): in seven lean, healthy young men, 5 g of cinnamon taken with an oral glucose tolerance test (OGTT) cut the glucose response by 13%, and 5 g taken 12 hours earlier cut it by 10% ^[27].

Rachid et al. (2022): in 36 adults with type 2 diabetes, an aqueous cinnamon extract (6 g/100 mL) taken straight after an OGTT did not change the glucose response compared with the OGTT alone ^[28].

Wickenberg et al. (2012): in ten people with impaired glucose tolerance, 6 g of Ceylon (C. zeylanicum) in capsules had no significant effect on glucose or insulin during an OGTT ^[29].

Meta-Analysis

Allen et al. (2013): a meta-analysis of 10 trials (n = 543 patients) using cinnamon doses of 120 mg/d to 6 g/d for 4 to 18 weeks ^[30]. Cinnamon lowered fasting plasma glucose (-24.59 mg/dL; 95% CI, -40.52 to -8.67 mg/dL), total cholesterol, LDL cholesterol and triglycerides, and raised HDL cholesterol, but had no significant effect on HbA1c (-0.16%; 95% CI -0.39% to 0.02%) ^[30]. Results varied widely between trials, and the best dose and duration were unclear ^[30].

de Moura et al. (2025): a larger meta-analysis of 28 trials lasting 30 to 120 days, with 3,054 patients with type 2 diabetes ^[67]. Cinnamon lowered fasting glucose (WMD: -15.26 mg/dL; 95% CI: -22.23 to -8.30) and HbA1c (WMD: -0.56; 95% CI: -0.99 to -0.13), again with large differences between trials ^[67]. In subgroup analyses, only doses of 2 g a day or less lowered HbA1c ^[67]. An umbrella review of 21 meta-analyses reached similar conclusions for fasting glucose and lipids ^[34].

Synthesis

The evidence for cinnamon in type 2 diabetes is inconsistent. Pooled trials point to lower fasting glucose, and the newer meta-analysis also found a small fall in HbA1c, but the trials differ widely and many are small ^{[30, 67]}. The best-known positive trial is now under an expression of concern that questions the plausibility of its data, and the publisher could not reach its authors ^[69]. Most positive trials gave cinnamon alongside diabetes medicines. NCCIH judges that higher quality research is needed before cinnamon can be said to help diabetes ^[68].

Blood Sugar Control in Prediabetes

Several studies have tested cinnamon in people with prediabetes or raised fasting glucose, with modest results.

Ziegenfuss et al. (2006): 22 people with prediabetes and the metabolic syndrome took 500 mg/d of Cinnulin PF or placebo for 12 weeks ^[13]. Compared with placebo, fasting glucose fell 8.4% (116.3 to 106.5 mg/dL), systolic blood pressure fell 3.8% (133 to 128 mm Hg) and lean mass rose 1.1% (53.7 to 54.3 kg) ^[13]. Blood chemistry showed no significant changes between groups ^[13].

Anderson et al. (2016): in China, 173 adults with raised blood glucose were enrolled (137 completed) and took CinSulin 250 mg or placebo twice a day for two months ^[14]. Fasting glucose fell from 8.85 to 8.19 mmol/L with the extract and from 8.57 to 8.44 mmol/L with placebo ^[14]. Glucose 2 hours after a carbohydrate load, fasting insulin and HOMA-IR (an insulin resistance score) also fell with the extract compared with placebo ^[14].

Romeo et al. (2020): adults with prediabetes took cinnamon 500 mg or placebo thrice daily for 12 weeks (n = 27/group) ^[31]. Fasting glucose rose on placebo but stayed stable on cinnamon, a between-group difference of 5 mg/dL ^[31]. Glucose tolerance improved from baseline with cinnamon, and there were no serious adverse events ^[31].

Zelicha et al. (2024): 18 adults with obesity and prediabetes (mean age 51.1; mean fasting glucose 102.9 mg/dL) took cinnamon (4 g/d) or placebo for 4 weeks each in a crossover trial ^[32]. Continuous glucose monitoring showed lower 24-hour glucose with cinnamon, and smaller glucose peaks (a rise of 9.56 versus 11.73 mg/dL) ^[32]. Digestive symptoms did not differ from placebo ^[32].

Synthesis

In prediabetes, small trials of water extracts and of ground cinnamon show modest falls in fasting glucose or better glucose control over weeks ^{[13, 14, 31, 32]}. The effects are small, and none of these trials shows that cinnamon can replace lifestyle change or medicine.

Cholesterol and Lipid Effects

Most lipid data come from diabetes trials, where lipids were secondary outcomes, plus meta-analyses.

The Khan et al. (2003) trial reported falls in triglycerides, LDL and total cholesterol at 1, 3 or 6 g a day, but it is under an expression of concern ^{[20, 69]}. In the Lu et al. (2012) trial, only the 120 mg extract dose lowered triglycerides, and cholesterol did not change ^[21].

The Allen et al. (2013) meta-analysis found lower total cholesterol (-15.60 mg/dL; 95% CI, -29.76 to -1.44 mg/dL), LDL cholesterol (-9.42 mg/dL; 95% CI, -17.21 to -1.63 mg/dL) and triglycerides (-29.59 mg/dL; 95% CI, -48.27 to -10.91 mg/dL) in type 2 diabetes ^[30]. A 2024 meta-analysis across trials found no significant overall effect on LDL cholesterol (WMD, -2.48; 95% CI, -9.70, 4.72), total cholesterol or HDL cholesterol, but a small fall in triglycerides (WMD, -6.88; 95% CI, -12.62, -1.15) ^[36]. In rats fed a high-fat diet, a cinnamon polyphenol extract lowered blood lipids and liver oxidative stress ^[35].

Antioxidant and Anti-Inflammatory Effects

In rats on a high-fat diet, a cinnamon polyphenol extract reduced markers of inflammation and oxidative stress ^[35].

Human evidence: a meta-analysis of 12 trials using 1.5 to 4 g/day of cinnamon powder found lower C-reactive protein (CRP) (WMD: -2.22 mg/L, 95% CI: -3.74, -0.69) and malondialdehyde (MDA), a marker of oxidative stress, and higher total antioxidant capacity ^[65].

Shishehbor et al. (2018): 36 women with rheumatoid arthritis took 4 capsules of either 500 mg cinnamon powder or placebo daily for 8 weeks ^[40]. Compared with placebo, cinnamon lowered CRP and TNF-alpha, the Disease Activity Score (DAS-28), pain scores and the number of tender and swollen joints ^[40]. Diastolic blood pressure was also lower ^[40].

These effects might contribute to the blood pressure changes described in the next section, but that link is unproven.

Blood Pressure

Evidence for cinnamon's effect on blood pressure is limited and comes mainly from secondary outcomes in diabetes trials.

In the Akilen et al. (2010) trial, systolic blood pressure fell from 132.6 to 129.2 mmHg and diastolic from 85.2 to 80.2 mmHg with 2 g a day of cinnamon, compared with little change on placebo ^[22]. In the Ziegenfuss et al. (2006) trial, Cinnulin PF lowered systolic blood pressure from 133 to 128 mm Hg in people with prediabetes ^[13].

However, the Wainstein et al. (2011) trial found that an apparent fall in systolic blood pressure with 1,200 mg/day of cinnamon was explained by regression to the mean ^[26].

A meta-analysis of 9 trials in 641 people found lower systolic (WMD: -6.23 mmHg, 95% CI: -10.69 to -1.77) and diastolic blood pressure (WMD: -3.93 mmHg, 95% CI: -6.33 to -1.52) with cinnamon ^[66].

Body Weight and Obesity

Evidence on body composition is preliminary.

In the Ziegenfuss et al. (2006) Cinnulin PF trial, lean mass rose 1.1% over 12 weeks ^[13].

A meta-analysis of 12 trials in 786 people found small falls in body weight (WMD: -1.02 kg, 95% CI: -1.66 to -0.38), BMI and waist circumference with cinnamon ^[41]. These changes are small, and NCCIH says it is unclear whether cinnamon helps weight loss ^[68].

Antimicrobial Activity

In laboratory tests, Ceylon cinnamon bark and cinnamaldehyde inhibited Candida yeasts, including fluconazole-resistant strains ^[44], and cinnamon oil killed Staphylococcus epidermidis biofilms ^[42].

In a pilot study, five people with HIV and oral thrush (oral candidiasis) took a commercial cinnamon preparation for one week, and three improved ^[44]. The authors called for clinical trials.

Evidence for antimicrobial effects in people is limited to this small pilot study.

Cognitive Function

In laboratory tests, cinnamon PACs blocked the build-up of advanced glycation end products (AGEs) ^[45]. AGEs are implicated in diabetic complications, atherosclerosis and Alzheimer's disease ^[45].

There is no clinical evidence that cinnamon improves memory or thinking in people, and NCCIH says research does not clearly support cinnamon for any health condition ^[68].

Gastrointestinal Effects

Limited evidence suggests possible benefits for diarrhea.

In two rat models of diarrhea-predominant IBS (IBS-D), an aqueous cinnamon extract reduced bowel symptoms and gut pain, partly by lowering serotonin (5-HT) production through the enzyme Tph1 ^[49].

In an 8-week randomized controlled trial in 70 people with diarrhea symptoms, a Cinnamomum cassia water extract (three 400 mg capsules twice daily) slowed colonic transit time (p = 0.019) and changed the gut microbiota compared with placebo ^[50].

Larger trials would be needed to confirm a benefit for IBS or other bowel disorders.

4. Recommended Dosing

By Indication

Type 2 diabetes (alongside medication), doses used in trials:

• Cinnamon: 1 g a day ^[23], 2 g a day ^[22], or 1, 3 or 6 g a day ^[20]
• Cinnamon extract: 120 mg or 360 mg a day ^[21]
• Ceylon (C. zeylanicum) bark: 1.5 g a day ^[11]

Prediabetes / raised fasting glucose, doses used in trials:

• Cinnulin PF extract: 500 mg a day ^[13]
• CinSulin extract: 250 mg twice a day ^[14]
• Cinnamon: 500 mg three times a day ^[31]

Around meals:

• Ground cinnamon stirred into water and taken just before a meal blunted the glucose spike after that meal in one trial ^[12]

Dosing Considerations

• Studied range: trials in type 2 diabetes used cinnamon doses of 120 mg a day up to 6 g a day, for 4 to 18 weeks ^[30]
• Upper end: 6 g a day was given for 40 days in one trial ^[20]; long-term use of cassia at high doses raises coumarin intake ^{[10, 19]}
• Coumarin limits: the tolerable daily intake for coumarin is 0.1 mg per kg of body weight, and heavy users of cassia cinnamon may reach it ^[10]. Ceylon cinnamon or a cassia water extract lowers coumarin intake ^[29].
• Form matters: cinnamon stirred into water acted faster than capsules on the glucose spike after a meal ^[12]

How to Read a Cinnamon Supplement Label

Key information to check:

1. Species of cinnamon: many products do not state it ^[68]. Ceylon has much less coumarin than cassia ^[19].

To check whether a product has been independently tested for quality, see ConsumerLab (consumerlab.com) or Labdoor (labdoor.com).

5. Safety and Side Effects

General Safety Profile

Cinnamon is likely safe in the amounts used in food ^[68]. Used in larger amounts or for long periods, it is sometimes linked to side effects, most often stomach problems or allergic reactions ^[68].

Common Side Effects

A systematic review of adverse events found 38 clinical trials, five of which reported adverse events, plus case reports and spontaneous reports including 160 adverse events ^[51]. The most frequent were gastrointestinal disorders and allergic reactions, mostly self-limiting ^[51]. The authors advise clinical monitoring of medicinal use at larger doses or for longer periods ^[51].

Coumarin Toxicity

The main safety concern with cinnamon, particularly cassia, is long-term coumarin intake ^{[10, 68]}.

Safe intake thresholds:

• The European Food Safety Authority set a tolerable daily intake (TDI) of 0.1 mg per kg of body weight for coumarin, and an analysis of human data confirmed it ^[10]
• Heavy consumers of cassia cinnamon may reach a daily coumarin intake equal to the TDI ^[10]
• A subgroup of people is more susceptible to coumarin's liver toxicity than animals are, for reasons that are not yet known ^[10]
• Cassia cinnamon can contain up to 1% coumarin, and the body absorbs coumarin from cinnamon almost as well as pure coumarin, so the TDI applies to cinnamon foods ^[71]
• A Norwegian assessment set a stricter TDI of 0.07 mg per kg; adults drinking cinnamon tea and taking cinnamon supplements could exceed it, and in some intake scenarios coumarin intake could exceed it 7- to 20-fold ^[70]

Species-specific risk:

• Ceylon cinnamon: trace or no coumarin ^{[19, 68]}
• Cassia cinnamon: high coumarin in tested powders (mean 2,650 to 7,017 mg per kg across brands) ^[19]. Most cassia does not contain enough coumarin to cause harm, but some products are high, and long-term use may be a problem for people with liver disease ^[68]

Anticoagulant Effects

The authors of one case report suggest coumarin may block vitamin K recycling, so that several clotting factors are not activated, and they linked a patient's bleeding after surgery to dietary coumarin ^[52]. The second case below, in a man on the blood thinner dabigatran, stands apart: he also took ginger, and how the herbs might have caused his bleeding is not known ^[9].

Case report: a 49-year-old man who had taken a tablespoon of Ceylon cinnamon daily for ten months bled inside the abdomen after bowel cancer surgery ^[52]. His haemoglobin fell from 17.4 g/dL to 8.0 g/dL over the next four days and his INR was 1.59 ^[52]. The authors attributed the bleeding to dietary coumarin ^[52].

Case report: an 80-year-old man on dabigatran vomited blood and passed black stools three days after starting a boiled mixture of ginger and cinnamon ^[9]. He died of the bleeding within 24 hours despite a reversal agent ^[9]. Because he took both herbs, the effect cannot be put down to cinnamon alone. If you vomit blood or pass black stools, call your local emergency number (111 in NZ, 000 in Australia, 911 in the US, 999 in the UK).

Liver Damage Risk (Drug Interaction)

Case report: a 73-year-old woman who had taken a statin for many months developed hepatitis about 1 week after starting cinnamon supplements ^[53]. Both were stopped; she later resumed the statin without problems ^[53]. The authors advise against combining cinnamon supplements with drugs that can harm the liver ^[53].

If you take a statin, ask your doctor before taking cinnamon supplements. Stop and see a doctor promptly if you get abdominal pain, vomiting or yellow skin or eyes.

Edema

Cinnamon bark powder activates the same receptors (PPARs) as thiazolidinedione drugs, which cause fluid retention ^[54].

Case report: an adult man developed edema while taking 1000 mg of cinnamon bark powder daily, and it resolved after he stopped ^[54]. The author warns that cinnamon bark powder could cause fluid retention and possibly worsen heart failure ^[54].

If you have heart failure, ask your doctor before taking cinnamon, and report new ankle swelling or breathlessness.

Other Reported Adverse Effects

• Rosacea flare: a 68-year-old woman with type 2 diabetes had a severe rosacea flare 2 weeks after starting cinnamon oil pills ^[55]
• Allergic reactions: cinnamaldehyde is mostly linked to contact allergy ^[64]. Allergic reactions inside the mouth from gum, candy, toothpaste and food are uncommonly reported ^[57]. Anaphylaxis to cinnamon in food has been reported ^[64]. For swelling of the face, lips or throat, or trouble breathing, call your local emergency number (111 in NZ, 000 in Australia, 911 in the US, 999 in the UK)
• The "cinnamon challenge": this internet dare with dry cinnamon powder is unsafe, and serious harm is possible ^[68]

Lead Contamination

In 2023, the FDA found lead, and later chromium, in the cinnamon used in a brand of applesauce pouches, and the product was recalled ^[60]. From November 2023 to April 2024, 566 cases of raised blood lead were reported across 44 states, the District of Columbia and Puerto Rico, 55% in children aged under 2 years ^[60].

Special Populations

• Pregnancy and breastfeeding: cinnamon in food amounts appears safe in pregnancy, but larger amounts of Ceylon cinnamon are considered unsafe ^[68]. Little is known about larger amounts of either type while breastfeeding ^[68]
• Children: supplement doses have not been well studied in children; ask a doctor before giving them
• Liver disease: long-term use of cassia cinnamon may be a problem for people with liver disease ^[68]; ask your doctor first
• Surgery: cinnamon was linked to bleeding after surgery in one case ^[52]. Tell your surgeon if you take cinnamon supplements ^[52].

6. Drug Interactions

Cinnamon may interact with medicines in three ways: added glucose lowering, possible added bleeding risk, and possible liver harm with drugs that affect the liver. NCCIH also notes theoretical reasons to suspect interactions with an anticancer medicine and with nicotine ^[68].

Blood Sugar-Lowering Medications

Pooled trials suggest cinnamon may lower fasting glucose ^{[30, 67]}. Several positive trials gave it alongside diabetes medicines such as gliclazide ^{[21, 22]}. If you take insulin, a sulfonylurea or other diabetes medicines, ask your doctor whether you need closer glucose checks. Cinnamon bark powder acts on the same receptors as thiazolidinedione drugs, and a case report linked it to fluid retention ^[54].

Anticoagulant and Antiplatelet Drugs

The authors of one case report suggest coumarin may block vitamin K recycling ^[52]. A man on dabigatran died of bleeding after starting a ginger and cinnamon drink ^[9]. If you take warfarin, dabigatran or another blood thinner, or an antiplatelet drug such as aspirin or clopidogrel, check with your doctor or pharmacist before starting.

Hepatotoxic Drugs

A case report linked cinnamon supplements taken with a statin to hepatitis ^[53]. Its authors advise against combining cinnamon with drugs that can harm the liver ^[53].

Blood Pressure-Lowering Medications

Cinnamon may lower blood pressure slightly ^[66]. It could in theory add to blood pressure medicines, though no interaction has been documented.

General Guidance

• Cinnamon in food amounts is likely safe ^[68]
• If you take prescription medicines, check with your doctor or pharmacist before starting.
• If you take any medicine, talk with your health care provider before using cinnamon supplements ^[68]

7. Dietary Sources

Cinnamon is eaten as a spice rather than as a main source of nutrients.

Nutritional Composition of Ground Cinnamon (per 100 g)

USDA FoodData Central lists the full nutrient content of ground cinnamon.

Key Bioactive Components at a Glance

Sources: ^{[6, 10, 11, 19, 52]}

Culinary Uses

Cinnamon has a long history in cooking in many parts of the world ^[68]. It is used in baking, in drinks such as chai and mulled wine, and in savoury dishes such as curries and tagines.

Practical Considerations

• Cassia vs Ceylon in cooking: cassia is the usual supermarket cinnamon in North America ^[68]. For daily use, such as cinnamon on porridge every morning, Ceylon has much less coumarin ^[19]
• Sticks vs powder: coumarin varies widely in sticks too; in a German study, sticks from two packages ranged from below detection to about 10,000 mg per kg ^[72]