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Cinnamon
A spice made from the dried bark of Cinnamomum trees, including cassia and Ceylon cinnamon. As a supplement, it is promoted for diabetes and weight loss.
Explained simply · Last reviewed
What it is
Cinnamon is a spice made from the dried bark of several kinds of Cinnamomum tree. According to NCCIH, the US agency that studies complementary medicine, Ceylon cinnamon, known as “true” cinnamon, grows mainly in Sri Lanka. Cassia cinnamon, grown in parts of south-eastern Asia, is the most common type sold in North America.
More about Cinnamon
According to NCCIH, the US agency that studies complementary medicine, Ceylon cinnamon, known as “true” cinnamon, grows mainly in Sri Lanka. Cassia cinnamon, grown in parts of south-eastern Asia, is the most common type sold in North America.
NCCIH states that the bark, leaves, flowers, fruits and roots of cinnamon have a long history in traditional medicine and cooking in China, India, Persia and elsewhere. Cinnamon was thought to help with inflammation, nerve pain, heart disease, cough and other conditions. Today, it states, cinnamon products are promoted as dietary supplements for diabetes and weight loss.
LiverTox, the US government’s liver-injury database, states that cinnamon is sold as powders, tablets, soft gels, capsules and teas. Its main ingredient is cinnamaldehyde, with smaller amounts of other compounds, coumarin among them. LiverTox states that cinnamon is not approved for any medical condition in the United States.
NCCIH notes that there have been many studies of cinnamon, especially for diabetes, but that they are hard to interpret because it is often unclear which species or part of the plant was tested.
The ratings below cover blood sugar in type 2 diabetes, blood fats, blood pressure, body weight and a nasal spray for hay fever.
Also known as: Cinnamomum, cassia cinnamon, Ceylon cinnamon, Cinnamomum cassia, Cinnamomum verum, Cinnamomum zeylanicum, cinnamon bark
At a glance
Safety: known risks and 3 groups who should avoid it or take extra care. See Safety ↓Claims made about Cinnamon, and how strong the evidence is for each:
- Lowers blood sugar in type 2 diabetesEvidence rating: Limited
- Improves cholesterol and other blood fatsEvidence rating: Limited
- Lowers blood pressureEvidence rating: Limited
- Helps with weight lossEvidence rating: Insufficient
- Eases hay fever symptoms, as a nasal spray of Ceylon cinnamon extractEvidence rating: Limited
Each rating follows our published rules and the sources cited for it. We don’t add our own medical judgment. How we rate
Safety
Read this before the ratings below.
Risks
- NCCIH, the US agency that studies complementary medicine, states that cinnamon is likely safe in the amounts commonly used in foods as a spice or flavoring. It states that in larger amounts or over long periods cinnamon is sometimes associated with side effects, most commonly digestive problems or allergic reactions.
- NCCIH states that interactions between coumarin, a chemical found in cassia cinnamon, and the liver have been reported. It states that cassia does not usually contain enough coumarin to cause significant problems, but that some cassia products contain high levels, and that prolonged use could be an issue for sensitive people, such as those with liver disease.
- LiverTox, the US government’s liver-injury database, rates cinnamon a “possible rare cause of clinically apparent liver injury”. It reports at least three published cases of acute liver injury attributed to cinnamon, none with a repeat exposure to confirm it, and in some of them other diagnoses were “possible, if not more likely”. It states that the mechanism is not known but is possibly related to the coumarin in cinnamon preparations.
- EFSA, the European food safety agency, reports that liver toxicity “has been reported in a number of patients treated with coumarin” as a medicine. It states that there is much evidence for a group of people, a single-digit percentage, who are more susceptible than the animal species studied. It reports that Germany’s risk assessment body identified a specific exposure of concern: large amounts of cinnamon powder in capsules, sold as food supplements to reduce blood sugar in people with type 2 diabetes.
- NCCIH states that cinnamon powder should never be swallowed as part of the “cinnamon challenge”, an unsafe internet dare, because serious harm is possible. It states that some cinnamon oils or powders applied to the skin may cause irritation or contact dermatitis.
- NCCIH states that cinnamon products may not say which species or which parts of the plant they were made from, and that these differ in chemical composition in ways that can affect a product’s impact on people.
- A 2012 Cochrane review of diabetes trials found that adverse reactions to cinnamon taken by mouth were infrequent and generally mild. Its pooled analysis of adverse events drew on 4 of its 10 trials, and the reviewers rated how sure they are of that finding moderate.
Who should avoid it or take extra care
- Liver disease: NCCIH states that prolonged use of cassia cinnamon could be an issue for sensitive people, such as those with liver disease.
- Pregnancy and breastfeeding: NCCIH states that some studies suggest Ceylon and cassia cinnamon are safe in pregnancy in amounts commonly found in foods, but that Ceylon cinnamon in larger amounts during pregnancy is considered unsafe. It states that little is known about whether larger amounts are safe while breastfeeding.
- People taking medicines: NCCIH states that, according to research it partly funded, there are theoretical reasons to suspect that some components of cinnamon may interact with an anticancer medicine or with nicotine. It does not name the medicine. It advises anyone who takes any medicine to talk with a health care provider before using cinnamon, because “some herbs and medicines interact in harmful ways”.
Safety sources: Source [1]Source [2]Source [3]Source [4]
What the evidence says
Each claim is rated on its own evidence. Ratings follow the scale on our methodology page.
Lowers blood sugar in type 2 diabetes Evidence rating: Limited
People with type 2 diabetes take cinnamon hoping it will bring their blood sugar down.
Reviews disagree: some found lower fasting blood sugar in type 2 diabetes, at low certainty where graded; one found lower HbA1c at moderate certainty, and three found no clear change.
This claim is about laboratory measures of blood sugar: fasting blood sugar, and HbA1c, which reflects average blood sugar over recent months. It is not about diabetes complications. A 2012 Cochrane review included 10 randomized trials in 577 people with diabetes, one of them in teenagers with type 1 diabetes. Most trials gave cassia cinnamon as tablets or capsules, for 4 to 16 weeks.
The Cochrane reviewers found no significant difference in HbA1c, rating how sure they are (certainty) moderate. They call the effect on fasting blood sugar inconclusive, and judged all but two trials at high or unclear risk of bias. They conclude that “there is insufficient evidence to support the use of cinnamon for type 1 or type 2 diabetes mellitus.” A comment published with the review argued that it analyzed the wrong measures. The authors replied that they followed Cochrane’s advice. They added that the change to one trial’s figures the comment proposed would alter the fasting blood sugar result negligibly.
Later reviews in type 2 diabetes disagree. A 2013 meta-analysis of 10 trials found lower fasting blood sugar but no significant change in HbA1c. A 2022 meta-analysis found lower fasting blood sugar, HbA1c, insulin and insulin resistance (HOMA-IR). It rated certainty low for fasting blood sugar, insulin and HOMA-IR, and moderate for HbA1c. It describes 14 of its trials as using cinnamon powder and one a water-based extract. Its abstract counts 16 trials, its results 15.
A 2023 meta-analysis of 15 trials in people with type 2 diabetes found no significant effect on fasting blood sugar or HbA1c. It reports lower fasting blood sugar only in a subgroup of trials using smaller amounts. It did not rate certainty.
NCCIH, the US agency that studies complementary medicine, states that it is unclear whether cinnamon supplementation helps with diabetes. It says higher quality research would be needed. Because the reviews disagree, this page takes the lower reading. It rates the claim on the lowest certainty given to these outcomes.
Improves cholesterol and other blood fats Evidence rating: Limited
People take cinnamon hoping it will lower their cholesterol and other blood fats.
Five reviews found lower triglycerides; they disagree on LDL, HDL and total cholesterol, and where graded, certainty ranges from very low to moderate.
This claim is about blood fat levels, which are markers, not heart attacks or strokes. In people with type 2 diabetes, three meta-analyses agree on triglycerides. A 2013 review and a 2022 review found lower total cholesterol, LDL (“bad”) cholesterol and triglycerides, and higher HDL (“good”) cholesterol. The 2022 review rated certainty moderate for each. A 2023 review found lower triglycerides and LDL and higher HDL, but no significant change in total cholesterol.
Two reviews pooled adults with a wider range of conditions, such as diabetes, fatty liver disease and polycystic ovary syndrome. A 2025 meta-analysis of 49 trials found improvements in all four measures, but rated certainty very low for every outcome. It judged 43 of the 49 trials at high risk of bias, and found signs of publication bias for LDL, total cholesterol and triglycerides. Its text and its tables give different estimates for these three measures, and this page quotes neither.
A 2024 meta-analysis of 10 trials found lower triglycerides, but no significant change in LDL, HDL or total cholesterol. It did not rate certainty. Because the reviews disagree, this page rates the claim on the lowest certainty they give these outcomes.
Lowers blood pressure Evidence rating: Limited
People take cinnamon hoping it will bring their blood pressure down.
A 2025 review found lower blood pressure at very low certainty, and removing one trial made its systolic result non-significant; LiverTox says controlled trials conflict.
A 2025 meta-analysis pooled 10 trials for diastolic blood pressure and 11 for systolic blood pressure. The people in them had conditions such as type 2 diabetes, prediabetes, metabolic syndrome or high blood pressure. Both readings were lower with cinnamon than in the comparison groups. Results varied widely between trials.
The reviewers rated certainty very low for both. Leaving out one trial at a time, removing a single trial made the systolic result no longer significant. Split by type of cinnamon, each named type held one or two trials. Five of the 10 diastolic trials and six of the 11 systolic trials did not state the type. The authors write that the effects “should be interpreted with caution and considered as possible rather than definitive.”
LiverTox, the US government’s liver-injury database, states that some studies have suggested cinnamon might improve blood pressure in people with high blood pressure. It adds that properly controlled trials “have yielded conflicting results”. This page rates the claim on the review’s very low certainty.
Sources: Source [1]Source [2]
Helps with weight loss Evidence rating: Insufficient
People take cinnamon hoping it will help them lose weight.
A 2025 review found no significant change in weight or BMI, at very low certainty; a 2022 review in type 2 diabetes found lower BMI, at low certainty; NCCIH says it is unclear whether it helps.
A 2025 meta-analysis pooled 16 trials that measured body weight and 23 that measured body mass index (BMI), in adults with a range of conditions. Neither changed significantly with cinnamon, and nor did body fat. Waist size was smaller, in 13 trials. The reviewers rated certainty very low for every one of these measures. Leaving out single trials changed two results: without one trial, body weight was significantly lower, and without another, body fat was.
A 2022 meta-analysis in people with type 2 diabetes found lower BMI with cinnamon, in seven trials, and rated that low certainty. NCCIH, the US agency that studies complementary medicine, states that it is unclear whether cinnamon supplementation helps with weight loss. It says higher quality research would be needed.
A result that is not statistically significant, at very low certainty, is too little evidence to show an effect. It is not evidence that there is none. Because the sources differ, this page takes the lower reading and rates the claim insufficient.
Sources: Source [1]Source [2]Source [3]
Eases hay fever symptoms, as a nasal spray of Ceylon cinnamon extract Evidence rating: Limited
People with hay fever use a nasal spray containing Ceylon cinnamon extract hoping it will ease their symptoms.
NCCIH states that early research suggests a nasal spray of Ceylon cinnamon extract might ease hay fever symptoms, but that more reliable evidence is needed.
This claim is about a nasal spray, not cinnamon taken by mouth. NCCIH, the US agency that studies complementary medicine, states that Ceylon cinnamon is promoted for allergic rhinitis (hay fever). It states that preliminary research indicates that a nasal spray containing Ceylon cinnamon extract “might improve symptoms”, but that “more reliable evidence is needed to confirm this initial result.”
NCCIH’s key references include one placebo-controlled trial of such a spray. No review of this use was found that could be cited here, so this page rates the claim on the NCCIH statement.
Sources: Source [1]
Which form the evidence used
Supplements are sold in several forms. This is what the sources on this page say about them — which form the research used, and any comparison those sources themselves made. Where they made none, this page does not rank the forms.
Cassia cinnamon (Cinnamomum cassia, also called Cinnamomum aromaticum), What the sources supportDetails
NCCIH states that cassia is the most common type sold in North America. A 2012 Cochrane review of diabetes trials reports that 7 of its 10 trials used cassia. It states that it cannot draw conclusions about other species. NCCIH states that cassia contains coumarin, and that some cassia products contain high levels of it. EFSA, the European food safety agency, states that, at least in Germany, the cinnamon mainly used as a flavoring is cassia, which contains relatively high concentrations of coumarin. LiverTox states that coumarin varies greatly between preparations, and that “minimal or only low concentrations are found in C. verum and C. cassia.” The sources differ on cassia; this page does not settle it. Source [1]Source [2]Source [3]Source [4]
Ceylon cinnamon (Cinnamomum verum, also called Cinnamomum zeylanicum), Details
NCCIH calls Ceylon “true” cinnamon and states that it may contain a trace amount of coumarin. The 2012 Cochrane review states that it is unable to draw any conclusions about species of cinnamon other than cassia. A 2025 review split its results by type of cinnamon; each Ceylon subgroup held three trials or fewer. No cited source compares how well the two types work. Source [1]Source [2]Source [3]
Sources
- Cinnamon for diabetes mellitusCochrane Database of Systematic Reviews, 2012 · Meta-analysis · Primary source · Certainty: moderate
- Cinnamon Use in Type 2 Diabetes: An Updated Systematic Review and Meta-AnalysisAnnals of Family Medicine, 2013 · Meta-analysis · Primary source
- Efficacy of cinnamon supplementation on glycolipid metabolism in T2DM diabetes: A meta-analysis and systematic reviewFrontiers in Physiology, 2022 · Meta-analysis · Primary source · Certainty: low
- The Effect of Cinnamon on Glycolipid Metabolism: A Dose–Response Meta-Analysis of Randomized Controlled TrialsNutrients, 2023 · Meta-analysis · Primary source
- CinnamonNational Center for Complementary and Integrative Health, NIH, 2024 · Health authority summary · Primary source
- The effect of cinnamon supplementation on cardiovascular risk factors in adults: a GRADE assessed systematic review, dose–response and meta-analysis of randomized controlled trialsJournal of Health, Population and Nutrition, 2025 · Meta-analysis · Primary source · Certainty: very low
- Effects of Cinnamon Supplementation on Lipid Profile: A Systematic Review and Meta-Analysis of Randomized Controlled TrialsClinical Nutrition Research, 2024 · Meta-analysis · Primary source
- CinnamonLiverTox: Clinical and Research Information on Drug-Induced Liver Injury, National Institute of Diabetes and Digestive and Kidney Diseases, 2026 · Health authority summary · Primary source
- Coumarin in flavourings and other food ingredients with flavouring properties - Scientific Opinion of the Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food (AFC)EFSA Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food (EFSA Journal), 2008 · Health authority summary · Primary source
Page history
Show all 2 changes to this page
- — Published.
- — Drafted. Lowering blood sugar in type 2 diabetes, improving cholesterol and other blood fats, lowering blood pressure and easing hay fever as a nasal spray rated limited; helping with weight loss rated insufficient.