Cinnamon is a spice from the bark of Cinnamomum trees. Human studies suggest small changes in blood sugar and some cardiometabolic measures in some groups, but results are mixed and the National Center for Complementary and Integrative Health says research does not clearly support cinnamon for any health condition.
Ceylon cinnamon and cassia cinnamon are different forms, and many studies do not clearly identify the species or plant part used. That makes it hard to apply one study’s result to every cinnamon powder, tea, capsule, or extract.
Quick facts on cinnamon studies
| Question | What the studies report |
|---|---|
| Forms studied | Oral cinnamon preparations, including capsules; studies do not always clearly identify the cinnamon species or plant part. |
| Doses studied | A 2012 review reported a mean of 2 g daily. A 2025 type 2 diabetes review compared doses at or below 2 g/day with doses above 2 g/day. |
| Typical study length | Type 2 diabetes trials in a 2025 review lasted 30 to 120 days. An earlier review reported 4 to 16 weeks. |
| Main studied uses | Blood sugar and related metabolic measures; blood pressure and other cardiovascular risk markers; and markers in women with polycystic ovary syndrome (PCOS). |
| Bottom line | Findings can be modest, and study differences limit firm conclusions. |
A meta-analysis combines results from several studies. It can show a pattern, but it cannot remove important differences in the cinnamon form, dose, participants, and outcomes.
What do human studies show?
Blood sugar in type 2 diabetes
The largest recent review located 28 randomized controlled trials with 3,054 adults and older adults with type 2 diabetes. A randomized controlled trial compares an intervention with a control group. Trials lasted 30 to 120 days. The review found lower fasting glucose, post-meal glucose, HbA1c, and HOMA-IR, a measure of insulin resistance, among participants taking cinnamon. Results varied greatly across several outcomes, including fasting and post-meal glucose and HbA1c. The 2025 systematic review reported that capsule studies and doses of 2 g/day or less were associated with several of these changes.
A separate quality-focused systematic review of 45 studies found that 62% reported a statistically significant improvement in at least one blood-glucose measure. After study-quality ranking, that share moved closer to 50%. Its authors described the likely effect on blood glucose as modest. The 2024 review did not combine all studies because their glucose measures differed too much.
Older findings were less favorable. A Cochrane review of 10 randomized trials, involving 577 people with type 1 or type 2 diabetes, found the effect on fasting glucose inconclusive and found no significant difference in HbA1c, insulin, or post-meal glucose. Those trials used mainly cassia preparations at a mean dose of 2 g daily for 4 to 16 weeks. The Cochrane review also found no trials reporting quality of life, diabetes complications, or mortality. Changes in a laboratory number are not automatically a patient benefit; surrogate outcomes explains that distinction.
Blood pressure, cholesterol, and related measures
A 2025 systematic review and dose-response meta-analysis pooled 49 studies in adults. It reported statistically significant reductions in waist circumference, blood pressure, fasting glucose, insulin, HbA1c, insulin resistance, LDL cholesterol, total cholesterol, triglycerides, C-reactive protein, and one oxidative-stress marker, with higher HDL cholesterol. The 2025 review described cinnamon as having potential as an adjunct for cardiovascular risk factors.
Results are not uniform. An umbrella review, which reviews earlier meta-analyses, found small average reductions of 2.36 mmHg in systolic blood pressure and 1.65 mmHg in diastolic blood pressure. It found no significant effect on C-reactive protein, malondialdehyde, or ICAM-1. The 2024 umbrella review said the limited number of studies and their differences require better research.
PCOS-related cardiometabolic markers
In 12 randomized trials in women with PCOS, a 2024 meta-analysis found an average weight difference of 0.47 kg, lower fasting blood sugar, and lower insulin-resistance scores after cinnamon. It also reported lower total and LDL cholesterol. The fasting-blood-sugar studies differed substantially from one another, and the authors called for larger studies using more consistent methods. The 2024 PCOS review reports the full results.
Hay fever and other promoted uses
The National Center for Complementary and Integrative Health reports preliminary research that a nasal spray containing Ceylon cinnamon extract might improve allergic-rhinitis symptoms. More reliable research is needed. The same agency says it remains unclear whether cinnamon supplementation helps with diabetes or weight loss.
What doses did researchers use?
These are study details, not a suggested dose. In the 2025 type 2 diabetes review, trials were grouped at 2 g/day or less and above 2 g/day; both groups showed lower fasting and post-meal glucose, while several other findings appeared in the 2 g/day-or-less group. The older Cochrane review reported a mean dose of 2 g daily.
Do not assume a teaspoon of kitchen cinnamon matches a study preparation. The National Center for Complementary and Integrative Health notes that products may not identify the cinnamon species or plant part, and those differences can change chemical composition and effects.
What are the downsides and interactions?
Cinnamon is likely safe in food amounts, according to the National Center for Complementary and Integrative Health. Larger amounts or long-term use are sometimes linked with stomach symptoms or allergic reactions. Dry cinnamon powder should not be consumed as part of the “cinnamon challenge”; serious harm is possible.
| Concern | What the official information says |
|---|---|
| Liver concerns | Cassia contains coumarin. Prolonged use may be a concern for sensitive people, including people with liver disease, especially when a product has high coumarin levels. Ceylon cinnamon may contain only a trace amount. |
| Skin use | Some topical cinnamon oils or powders may cause skin irritation or contact dermatitis. |
| Medicines | There are theoretical reasons that cinnamon components may interact with an anticancer medicine or nicotine. Herbs and medicines can interact harmfully. |
| Pregnancy and breastfeeding | Food amounts appear to have a different safety record from larger amounts. Larger amounts of Ceylon cinnamon during pregnancy are considered unsafe, and little is known about larger amounts while breastfeeding. |
The official source reports coumarin-related liver interactions, but it does not answer whether a particular person’s liver or kidney problem will reverse. If you have liver disease, take a medicine, are pregnant or breastfeeding, or are considering a larger-than-food amount, talk with a clinician or pharmacist before using cinnamon products.
Who should talk to a clinician first?
- People with liver disease, because prolonged cassia use may be an issue for sensitive people.
- People taking any medicine, especially an anticancer medicine or nicotine, because of possible interactions.
- People who are pregnant or breastfeeding and considering amounts beyond food use.
- People who have had an allergic skin reaction or other reaction to cinnamon.
What is still unknown?
It is often unclear which species or plant part a study tested. It is also unclear whether cinnamon supplementation helps with diabetes or weight loss, according to the National Center for Complementary and Integrative Health. Current research does not answer whether drinking cinnamon every day is right for every person, whether one cinnamon form works better than another for a particular goal, or whether changes in study markers lead to fewer health problems over time.
Cinnamon has a long history in food and traditional medicine, including in China, India and Persia (Iran).
How do you read a cinnamon label?
- Look for the amount: Check whether the label gives a cinnamon amount per serving. Study results cannot be matched to a product when its amount is not listed.
- Look for the form: Note whether it names bark, an extract, oil, powder, or another form. Studies and products may use different forms.
- Look for the species: Check whether it identifies Ceylon or cassia. The National Center for Complementary and Integrative Health says species and plant parts have important chemical differences.
- Question proprietary blends: If a blend gives only a combined total, ask the manufacturer how much cinnamon and which form it contains before ordering.
By ClinicalStudyConnect.com Research Desk
This article is for general information purposes only and does not constitute medical advice. Consult your doctor or qualified healthcare provider before making changes to your health routine.