GradedHealth

Does cinnamon help lower blood sugar?

Several meta-analyses link cinnamon to lower fasting blood sugar, but results are mixed, most trials are small, and some cassia cinnamon contains coumarin.

Published October 2026

Short answer

Early, limited evidence: cinnamon may lower fasting blood sugar a little in type 2 diabetes, but results conflict and the trials are small. Evidence grade C (Limited). Several meta-analyses of randomized trials show lower fasting blood sugar, but the Cochrane review found it inconclusive; downgraded for inconsistency and because fasting glucose and HbA1c are markers, not disease outcomes.

Key takeaways

  • Several meta-analyses report lower fasting blood sugar with cinnamon [1][2].
  • The 2012 Cochrane review called the fasting blood sugar effect inconclusive and found no significant change in HbA1c [3].
  • Results for HbA1c, a blood test of average blood sugar, are mixed: newer reviews show falls, older ones do not [1][4].
  • Cassia cinnamon contains coumarin, which can harm the liver in some people, and heavy users may reach the daily limit [5].
  • No trial in the Cochrane review reported illness or death, so the evidence does not show that cinnamon prevents diabetes complications [3].

The short version

Cinnamon may lower fasting blood sugar a little, but the evidence is early and inconsistent [1]. Several meta-analyses report lower fasting blood sugar with cinnamon [1][2], yet a 2012 Cochrane review called the effect inconclusive [3]. Results for HbA1c, a blood test of average blood sugar, are mixed as well [6].

What the studies show

A 2024 meta-analysis of 24 randomized trials in people with type 2 diabetes found significantly lower fasting blood sugar and HbA1c with cinnamon than with control, and no significant change in insulin [1].

A 2025 meta-analysis of 49 studies in adults also reported significant falls in fasting blood sugar and HbA1c [2].

An older 2013 meta-analysis of 10 trials with 543 people found fasting plasma glucose about 25 mg/dL lower, but no significant change in HbA1c [4].

The 2012 Cochrane review pooled 10 trials of 577 people with type 1 or type 2 diabetes. It found the effect on fasting glucose inconclusive, with no significant difference in HbA1c, insulin or after-meal glucose [3].

A 2023 dose-response meta-analysis of trials in type 2 diabetes found no significant effect on fasting glucose or HbA1c, although it found lower triglycerides and LDL cholesterol [7].

Two meta-analyses report lower blood sugar after meals [2][8].

Single trials differ. In a trial of 66 people with type 2 diabetes who all took the diabetes drug gliclazide, cinnamon extract lowered HbA1c and fasting glucose at both doses tested, while placebo did not [9]. In an eight-week trial of 44 people with type 2 diabetes, 3 grams a day changed neither fasting glucose nor HbA1c [10].

A 2019 trial of 140 people with type 2 diabetes found improvements in fasting glucose and HbA1c after three months of cinnamon bark capsules, with bigger changes in people with a BMI of 27 or more [11].

A 2025 trial of 210 people with type 2 diabetes tested Ceylon cinnamon extract at 250 mg or 500 mg for four months. Fasting glucose and HbA1c fell from baseline in both extract groups, and regression analysis found the extract a significant predictor of the changes [12].

In an 18-person crossover trial of adults with obesity and prediabetes, 4 grams a day of cinnamon spice for four weeks lowered 24-hour glucose compared with placebo, measured by continuous glucose monitors [13].

An umbrella review of 21 meta-analyses reported improved fasting glucose, with larger effects in people with diabetes or metabolic syndrome, and called for more well-designed trials [14].

A 2024 review that ranked 45 studies for bias and quality found that the share with a significant positive result fell from 62% to close to 50% after ranking [15].

The nuances

Most trials used cassia cinnamon [3]. Ceylon cinnamon is a different species, and cassia can contain far more coumarin: up to 3.6 g/kg, against no more than 15 mg/kg in Ceylon [16].

Dose may matter. A 2025 review found HbA1c fell only at doses of 2 grams a day or less [8].

Results vary widely between trials. The 2013 review found high variation between trials for nearly all its results [4].

The trials are small and short. The 2013 review's trials ran for 4 to 18 weeks [4], and the Cochrane review found high or unclear risk of bias in most of its trials [3].

Fasting glucose and HbA1c are markers. No trial in the Cochrane review measured illness or death [3].

A 10-person crossover trial in people with impaired glucose tolerance found that 6 grams of Ceylon cinnamon did not change blood glucose or insulin after a 75-gram glucose drink [17].

Cassia cinnamon contains coumarin, which can harm the liver in some people [5]. Heavy users of cassia may reach the EFSA tolerable daily intake of 0.1 mg per kg of body weight [5], roughly 7 mg a day for a 70 kg adult.

A 2016 retrospective study of 129 Japanese outpatients taking herbal medicines with cinnamon bark found that 76% exceeded the daily limit. Abnormal liver tests were no more common in those above the limit than in those below it [18]. Because these were herbal medicines, the study cannot show whether cinnamon caused any liver changes.

Across seven trials with 256 people, cinnamon did not change liver enzymes overall. A lower ALT appeared in a subgroup with type 2 diabetes [19].

The 2025 Ceylon trial's authors say they hold a patent on the extract [12]. The Cochrane review reports no known conflicts of interest [3].

What this means for you

Cinnamon is a common culinary spice [16]. Trial doses ranged from about 120 mg to 6 grams a day, for 4 to 18 weeks [4].

If you take diabetes medicines, talk to your doctor before using cinnamon supplements regularly. One trial gave cinnamon alongside gliclazide, but its abstract does not report low blood sugar episodes [9]. We found no trial designed to test interactions with diabetes drugs.

No trial of cinnamon in pregnancy turned up in our search. A 2026 review describes a pilot study of spices in gestational diabetes and says larger studies are needed [20].

If you have liver disease, ask a doctor before taking cassia cinnamon regularly [5]. Our searches found no trial data on people with kidney disease.

For the full list of claims and safety notes, see the cinnamon topic page.

Go deeper

  • Cinnamon — Several meta-analyses report lower fasting blood sugar with cinnamon, mainly in type 2 diabetes.

References

  1. The effect of cinnamon supplementation on glycemic control in patients with type 2 diabetes mellitus: An updated systematic review and dose-response meta-analysis of randomized controlled trials.. Phytother Res, 2024.
  2. The effect of cinnamon supplementation on cardiovascular risk factors in adults: a GRADE assessed systematic review, dose-response and meta-analysis of randomized controlled trials.. J Health Popul Nutr, 2025.
  3. Cinnamon for diabetes mellitus.. Cochrane Database Syst Rev, 2012.
  4. Cinnamon use in type 2 diabetes: an updated systematic review and meta-analysis.. Ann Fam Med, 2013.
  5. Toxicology and risk assessment of coumarin: focus on human data.. Mol Nutr Food Res, 2010.
  6. Efficacy and safety of cinnamon in type 2 diabetes mellitus and pre-diabetes patients: A meta-analysis and meta-regression.. Diabetes Res Clin Pract, 2019.
  7. The Effect of Cinnamon on Glycolipid Metabolism: A Dose-Response Meta-Analysis of Randomized Controlled Trials.. Nutrients, 2023.
  8. Effects of cinnamon supplementation on metabolic biomarkers in individuals with type 2 diabetes: a systematic review and meta-analysis.. Nutr Rev, 2025.
  9. Cinnamon extract improves fasting blood glucose and glycosylated hemoglobin level in Chinese patients with type 2 diabetes.. Nutr Res, 2012.
  10. Effects of Cinnamon Consumption on Glycemic Indicators, Advanced Glycation End Products, and Antioxidant Status in Type 2 Diabetic Patients.. Nutrients, 2017.
  11. Efficacy of cinnamon in patients with type II diabetes mellitus: A randomized controlled clinical trial.. Clin Nutr, 2019.
  12. Efficacy and Safety of Cinnamomum zeylanicum (Ceylon cinnamon) for diabetes mellitus: a randomized, double blind, placebo-controlled clinical trial.. Diabetes Metab Syndr, 2025.
  13. Effect of cinnamon spice on continuously monitored glycemic response in adults with prediabetes: a 4-week randomized controlled crossover trial.. Am J Clin Nutr, 2024.
  14. The effects of cinnamon on patients with metabolic diseases: an umbrella review of meta-analyses of randomized controlled trials.. Front Nutr, 2025.
  15. A Systematic Review Evaluating Cinnamon's Effects on Glucose Utilizing a Ranking System to Assess Bias and Study Quality.. J Med Food, 2024.
  16. A critical appraisal of anti-hyperglycemic mechanisms, matrix-dependent bioavailability, and species-stratified safety of Cinnamomum spp. as functional food ingredients.. Food Res Int, 2026.
  17. Ceylon cinnamon does not affect postprandial plasma glucose or insulin in subjects with impaired glucose tolerance.. Br J Nutr, 2012.
  18. The Relation between Hepatotoxicity and the Total Coumarin Intake from Traditional Japanese Medicines Containing Cinnamon Bark.. Front Pharmacol, 2016.
  19. What is the influence of cinnamon supplementation on liver enzymes? A systematic review and meta-analysis of randomized controlled trials.. Phytother Res, 2021.
  20. [Role of spices in the management of diabetes and gestational diabetes].. Rev Med Suisse, 2026.