The evidence is mixed. Some meta-analyses suggest that cinnamon — especially the cassia variety at 1 to 6 grams per day — produces modest reductions in fasting glucose (5 to 25 mg/dL) and A1C (0.3 to 0.7 percent) in people with type 2 diabetes. Newer Cochrane reviews call the overall evidence inconclusive due to small studies and inconsistent results. Cinnamon is not a substitute for prescribed medication or lifestyle change, but it may be a low-cost adjunct for some people.
What Researchers Have Actually Studied
Interest in cinnamon for blood sugar took off in the early 2000s after a small study in people with type 2 diabetes reported reductions in fasting glucose, triglycerides, and LDL cholesterol with 1 to 6 grams of cassia cinnamon per day. Since then, dozens of randomized controlled trials and several systematic reviews have followed. Two of the most cited meta-analyses are Akilen et al. (2012) and Allen et al. (2013), both of which pooled small trials and reported statistically significant reductions in fasting glucose and A1C. The 2012 Cochrane review and a 2019 update concluded that the evidence is too inconsistent to support cinnamon as a treatment, citing small sample sizes, short durations, and varying preparations.
What the Numbers Look Like
| Outcome | Reported Effect Range (Meta-Analyses) | Confidence |
|---|---|---|
| Fasting glucose | Reduction of 5 to 25 mg/dL | Low to moderate; inconsistent |
| A1C | Reduction of 0.3 to 0.7 percent | Low; not seen in all studies |
| Postprandial glucose | Variable, sometimes reduced | Very low |
| LDL cholesterol | Small reductions in some trials | Very low |
| Triglycerides | Small reductions in some trials | Very low |
How Cinnamon Might Work
Several mechanisms have been proposed based on cell and animal studies:
- Insulin sensitization: compounds in cinnamon (especially methylhydroxychalcone polymer or MHCP) appear to enhance insulin signaling in cell models.
- Slowed gastric emptying: cinnamon may delay stomach emptying, blunting postprandial glucose rise.
- Inhibition of digestive enzymes: cinnamon polyphenols may inhibit alpha-amylase and alpha-glucosidase, slowing carbohydrate breakdown.
- Antioxidant effects: cinnamon polyphenols can reduce oxidative stress, which contributes to insulin resistance.
None of these mechanisms have been definitively confirmed as the source of the observed clinical effects, and the magnitude of any single mechanism is small.
Cassia vs. Ceylon Cinnamon
“Cinnamon” is not one plant. The two main commercial varieties have different safety profiles.
- Cassia cinnamon (Cinnamomum cassia): the most common grocery store variety in the US, also called Chinese or Saigon cinnamon. Stronger flavor, cheaper, and the type used in most positive studies. Contains 1 percent or more coumarin by weight.
- Ceylon cinnamon (Cinnamomum verum): “true cinnamon,” milder flavor, more expensive. Contains roughly 0.004 percent coumarin — about 250 times less than cassia.
Coumarin is a natural compound that, in high or sustained intake, can cause liver toxicity in sensitive individuals. The European Food Safety Authority set a tolerable daily intake of 0.1 mg per kg body weight per day. A 70-kg adult could exceed that limit with as little as 1 teaspoon (2 grams) of cassia cinnamon per day if taken regularly. For daily long-term use, Ceylon cinnamon is the safer choice.
What the Cochrane Review Concluded
The Cochrane review on cinnamon for diabetes concluded that there is insufficient evidence to support the use of cinnamon for type 1 or type 2 diabetes. The reviewers noted that the included trials were generally small, often short (12 to 16 weeks), used different cinnamon preparations and doses, and produced inconsistent results. Some trials showed meaningful glucose and A1C reductions; others showed no effect at all. Cochrane reviews are widely considered the most rigorous summary of medical evidence, and an “insufficient evidence” verdict means the question is not settled — not that cinnamon definitely does not work.
The NCCIH Position
The National Center for Complementary and Integrative Health notes that studies on cinnamon and blood sugar have produced conflicting results. NCCIH highlights potential coumarin-related liver concerns with cassia cinnamon at high or prolonged doses and recommends discussing supplements with a healthcare provider. The agency does not endorse cinnamon as a treatment for diabetes.
Where Cinnamon Fits in a Real Diabetes Plan
Cinnamon is not a stand-alone treatment. The interventions with the strongest evidence for prediabetes and type 2 diabetes are weight loss (5 to 10 percent of body weight), regular physical activity (150 minutes per week of moderate-intensity exercise), dietary patterns such as Mediterranean or DASH, and pharmacotherapy when indicated (metformin, GLP-1 agonists, SGLT2 inhibitors, insulin). Cinnamon, if it works at all, contributes a small effect on top of these. Our diet and nutrition hub covers the dietary patterns with the strongest evidence base, and the guide to reversing prediabetes outlines the lifestyle approach that produces meaningful results.
Practical Notes if You Want to Try Cinnamon
- Choose Ceylon cinnamon for daily use to minimize coumarin exposure.
- Start small: 1 to 2 grams per day (about half to one teaspoon) is reasonable.
- Take with food to reduce GI upset.
- Monitor your glucose if you have diabetes; let your prescriber know so doses of any glucose-lowering medication can be adjusted if needed.
- Avoid high-dose extracts long-term unless under medical supervision; potency can vary widely between products.
- Stop if you notice yellowing of the skin or eyes, dark urine, or right-upper-quadrant pain — these can be signs of liver irritation.
Drug Interactions to Watch For
Coumarin in cassia cinnamon shares structural similarities with some anticoagulants. While normal culinary use is unlikely to cause clinically significant interactions, high-dose cinnamon supplements may interact with warfarin and other blood-thinning medications. People taking glucose-lowering medications (insulin, sulfonylureas, GLP-1 agonists) could theoretically experience additive hypoglycemia, though this is rarely reported in trials. Tell your prescriber and pharmacist about any cinnamon supplement use.
The Bottom Line
Cinnamon may produce modest reductions in fasting glucose and A1C in some people with type 2 diabetes, with effects of roughly 5 to 25 mg/dL fasting glucose and 0.3 to 0.7 percent A1C in positive studies. The evidence is mixed and the Cochrane review calls it inconclusive. Ceylon cinnamon is safer than cassia for daily use due to lower coumarin content. Cinnamon is not a substitute for medication or lifestyle change, and any use should be discussed with your prescriber.
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting, stopping, or changing any medication or treatment plan.
