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Cinnamon
Cinnamon — what the European monograph actually supports, what it is not for, the form and how long it is meant to be used, side effects, and the 3 medicine interactions documented for it.
This is a reference page, not a diagnosis and not a prescription. Herbal products are real pharmacology: they have effects, side effects and interactions with medicines. Tell your doctor and your pharmacist everything you take, including teas and supplements, and never stop or change a prescribed medicine because of anything you read here.
What it is
Cinnamomum verum J.Presl (Ceylon) and Cinnamomum cassia (L.) J.Presl (cassia) — bark
Local names across the region this site serves: kaneel (ET) · kaneli (FI) · корица (RU).
Grouped here under Kitchen spices with a safety story. Regulatory position: Food and spice; the medicinal claim made for it is blood-glucose lowering.
What the evidence supports
The registered indication: Nothing that survives a systematic review. It is a spice with a real safety figure attached.
Two different barks are sold as cinnamon in Europe and the difference matters more than the flavour. Almost all cheap supermarket ground cinnamon is cassia, which contains substantially more coumarin than Ceylon or "true" cinnamon, where coumarin is present only in traces. Coumarin is not warfarin — warfarin is a synthetic derivative — but it is hepatotoxic in sensitive individuals at sustained high intakes. EFSA set a tolerable daily intake for coumarin of 0.1 mg per kilogram of body weight per day; for a 60 kg adult that is 6 mg a day, a threshold that heavy cassia use can pass, whether through cinnamon capsules taken for blood sugar or through a season of heavy baking. National food authorities have issued repeated advice on exactly this. On the blood-sugar claim that drives the capsule market, a Cochrane review of cinnamon for diabetes found insufficient evidence to support it, and later reviews have not converged either.
D — Popular claim unsupported, or safety dominates The better trials are negative, or the substance appears in the literature mainly for the harm it has caused.
What it is not for
Type 2 diabetes. If your glucose needs lowering, that is a treatable condition with treatments that work and are monitored.
Form, strength and how long
Ground bark as a spice, cinnamon sticks (quills — Ceylon quills are thin, layered and brittle; cassia is a single thick curl), capsules of cassia powder or extract, and cinnamon essential oil, which is a potent irritant.
Duration. As a spice, indefinitely. As a daily capsule taken for blood sugar, the coumarin question makes long-term use the wrong side of the risk-benefit line.
No gram figure appears on this page on purpose. The plant part, the extraction solvent and the drug-to-extract ratio together define a preparation, and a number taken from one does not describe another. The reasoning is set out on the hub; the amount that applies to you is the one printed on the pack you are holding, and a pharmacist will read it with you.
Side effects
Mouth irritation and contact allergy from cinnamon oil and high-cassia products — cinnamon-flavoured chewing gum and toothpaste are a recognised cause of oral lesions. Liver effects at sustained high coumarin intake in susceptible people.
Who should avoid it
Anyone with liver disease should keep cassia intake modest. Cinnamon supplements are not established in pregnancy.
Interactions with medicines
| Medicine or substance | What is described |
|---|---|
| Diabetes medicines and insulin | Taking cinnamon capsules for blood sugar while on glucose-lowering medicines is running an uncontrolled experiment with an unstandardised product. If you want to try it, tell whoever manages your diabetes so the numbers are read properly. |
| Anything else that stresses the liver | Sustained high cassia intake alongside other liver stressors is the scenario the coumarin limit exists for. |
| Anticoagulants and antiplatelets (warfarin, DOACs, aspirin, clopidogrel) | Coumarin is not warfarin, but the confusion is widespread and high-dose cassia products should still be mentioned if you are on an anticoagulant. |
The reverse view — start from the medicine rather than the plant — is in the medicine, food and alcohol interactions reference, and summarised for every herb on this site.
As a food
This one is also in the kitchen, so the nutrition figures are worth having next to the pharmacology: see the food data page for calories and nutrients per 100 g and per portion. Culinary amounts and medicinal preparations are different exposures, and the difference is usually the whole safety story.
Sources: European Food Safety Authority — scientific opinions on coumarin, green tea catechins and hydroxyanthracene derivatives · NIH National Center for Complementary and Integrative Health — herb fact sheets · checked 2026-09-06
Frequently asked questions
What is cinnamon used for?
Nothing that survives a systematic review. It is a spice with a real safety figure attached. Two different barks are sold as cinnamon in Europe and the difference matters more than the flavour. Almost all cheap supermarket ground cinnamon is cassia, which contains substantially more coumarin than Ceylon or "true" cinnamon, where coumarin is present only in traces. Coumarin is not warfarin — warfarin is a synthetic derivative — but it is hepatotoxic in sensitive individuals at sustained high intakes. EFSA set a tolerable daily intake for coumarin of 0.1 mg per kilogram of body weight per day; for a 60 kg adult that is 6 mg a day, a threshold that heavy cassia use can pass, whether through cinnamon capsules taken for blood sugar or through a season of heavy baking. National food authorities have issued repeated advice on exactly this. On the blood-sugar claim that drives the capsule market, a Cochrane review of cinnamon for diabetes found insufficient evidence to support it, and later reviews have not converged either.
Does cinnamon work?
Graded D here: The better trials are negative, or the substance appears in the literature mainly for the harm it has caused. Type 2 diabetes. If your glucose needs lowering, that is a treatable condition with treatments that work and are monitored.
How much cinnamon should I take?
This reference does not print gram figures, because they do not transfer between preparations of different extract strength. What can be said honestly is the form and the duration: Ground bark as a spice, cinnamon sticks (quills — Ceylon quills are thin, layered and brittle; cassia is a single thick curl), capsules of cassia powder or extract, and cinnamon essential oil, which is a potent irritant. As a spice, indefinitely. As a daily capsule taken for blood sugar, the coumarin question makes long-term use the wrong side of the risk-benefit line.
What are the side effects of cinnamon?
Mouth irritation and contact allergy from cinnamon oil and high-cassia products — cinnamon-flavoured chewing gum and toothpaste are a recognised cause of oral lesions. Liver effects at sustained high coumarin intake in susceptible people.
Does cinnamon interact with medicines?
Yes — documented for Diabetes medicines, Liver load, Anticoagulants, warfarin. Each one is described on this page, with a link to the medicine-side reference where one exists.
Others in kitchen spices with a safety story
Garlic
Relief of symptoms of mild circulatory complaints, in traditional-use preparations. Not the treatment of cardiovascular disease.
Nutmeg
Nothing medicinal. It is on this list because it is the kitchen spice that poisons people.
Green tea extract
Marketed for weight loss and metabolism. Neither claim survives review.
Chilli and cayenne (capsaicin)
Topical relief of muscle and joint pain in low-strength preparations; high-concentration capsaicin patches are licensed medicines for peripheral neuropathic pain.
Keep the whole list in one place
TempoLife logs supplements alongside food, sleep and how you actually felt — so the answer to "what are you taking?" is a screen, not a guess.