Does cinnamon lower blood sugar?

A little, in people with type 2 diabetes who take it as a supplement, and the evidence is less certain than the newest numbers look. A 2025 meta-analysis of 28 randomized trials in 3054 people with type 2 diabetes found cinnamon lowered fasting glucose by 15.26 mg/dL (95% CI -22.23 to -8.30) and HbA1c by 0.56. Most of those people were also taking diabetes medicine, and the trials disagreed sharply with one another. The 2012 Cochrane review of 10 trials found no significant effect on HbA1c and judged the evidence insufficient to support cinnamon for diabetes.

Unsettled. Fasting glucose falls in most of the pooled analyses. HbA1c, the measure that tracks blood sugar over months, is where they part ways. Some reviews find a fall of about half a point, others find none or one too small to matter. The trials are small and short, used doses from 120 mg to 6 g a day, and differed in risk of bias. That is why stricter and looser reviews of the same field reach different answers.

What the trials found

Fasting glucose and HbA1c in type 2 diabetes

The 2025 review of 28 trials ran from 30 to 120 days each. Beside the fall in fasting glucose it found after-meal glucose 39.22 mg/dL lower. Its abstract prints the HbA1c change of -0.56 with the unit mg/dL, which reads as a slip for percentage points. Heterogeneity was 88 percent for fasting glucose and 94 percent for HbA1c, so the trials did not tell one story. A 2024 dose-response review of 24 trials, much of it the same pool, found falls in fasting blood sugar and HbA1c on a standardized scale. A 2025 review of 49 trials in adults found the same direction for fasting glucose, HbA1c and after-meal glucose, again only as standardized effects.

The older reviews are less encouraging. A 2013 meta-analysis of 10 trials in 543 people found fasting glucose 24.59 mg/dL lower, and HbA1c changed by -0.16 percent (95% CI -0.39 to 0.02), which did not reach significance. A 2012 review of 6 trials in 435 people found HbA1c 0.09 points lower and fasting glucose 15 mg/dL (0.84 mmol/L) lower. A fall in HbA1c of 0.09 points is far below the 0.3 to 0.5 usually counted as clinically meaningful. The first review, in 2008, pooled 5 trials in 282 people with type 1 or type 2 diabetes and found no change in HbA1c or fasting glucose.

The Cochrane review, searched to January 2012, covered 10 trials in 577 people taking about 2 g a day for 4 to 16 weeks. It found no significant difference in HbA1c, insulin or after-meal glucose, and the effect on fasting glucose was inconclusive. It judged the risk of bias high or unclear in 8 of the 10 trials. A 2025 umbrella review of 21 meta-analyses concluded that cinnamon is linked with lower fasting glucose, with larger effects in diabetes and metabolic syndrome, and its abstract gives no pooled number.

Before diabetes, and after one dose

In a double-blind crossover trial in 18 adults with obesity and prediabetes, 4 g of cinnamon a day for 4 weeks lowered glucose over 24 hours on continuous monitors, compared with placebo. The abstract's effect size and interval do not match, so how large the difference was cannot be read from it, and the trial was 18 people after a run-in on a diet low in polyphenols. In 10 young obese women, a single 5 g dose of cassia cinnamon lowered the glucose peak 30 minutes after a glucose drink to 140 mg/dL, against 156 on placebo. It did not improve insulin sensitivity. In women with polycystic ovary syndrome, a meta-analysis of 5 trials found cinnamon lowered insulin resistance, a calculated index rather than a clinical outcome.

Who should be careful

In the Cochrane trials, adverse reactions to oral cinnamon were infrequent and generally mild. Those trials ran 4 to 16 weeks, too short to show slow harm to the liver. In the prediabetes trial, 4 g a day caused no more digestive symptoms than placebo. A review of adverse events concluded that cinnamon is safe as a spice, and that larger doses or longer use as a medicine should be clinically monitored.

Not for everyone. Cassia cinnamon can carry high levels of coumarin, which has been linked to liver problems. The US National Center for Complementary and Integrative Health says prolonged use of cassia could be an issue for sensitive people, such as those with liver disease. Food gives no protection here. In 24 volunteers, coumarin was absorbed from cinnamon in rice pudding at 54.7 percent and from cinnamon tea at 66.1, against 62.8 percent from a coumarin capsule.

If you take medicine for diabetes, a cinnamon supplement is a conversation with whoever prescribes it. NCCIH advises anyone on any medicine to talk with a clinician first, and most people in the trials above were already on diabetes drugs. We found no trial of cinnamon and blood sugar in pregnancy or in children.

What expert bodies say

NCCIH, in a page updated in November 2024, says it is unclear whether cinnamon supplementation is helpful for diabetes. We could not reach the 2026 diabetes care standards of the American Diabetes Association, so we do not report their position.

How we searched

What would change this answer

• A large, preregistered trial at low risk of bias, of one named species, Ceylon or cassia, at a fixed dose for 6 months or more, with HbA1c as the main outcome, in people on stable diabetes treatment. We found none registered.
• Trials that measure the coumarin in what they give, so that benefit and liver risk can be weighed for the same product.
• Any trial of cinnamon in the amounts people sprinkle on food.

What cinnamon contains and the rest of its evidence is on the cinnamon page.

Sources

1. ev-cibs-01 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials (PROSPERO CRD42022370332) · n = 3054
   Participants consuming cinnamon showed a significant reduction in fasting blood glucose (FBG) (WMD: -15.26 mg/dL; 95% CI: -22.23 to -8.30; I2 = 88%), postprandial glucose (WMD: -39.22 mg/dL; 95% CI: -63.90 to -14.55; I2 = 100%), HbA1c (WMD: -0.56 mg/dL; 95% CI: -0.99 to -0.13; I2 = 94%), and HOMA-IR (WMD = -0.76, 95% CI: -1.13 to -0.39; I2 = 22%) compared with the control group.
   
   Who: adults and older adults with type 2 diabetes in RCTs lasting 30 to 120 days
   Effect: fasting glucose WMD -15.26 mg/dL (95% CI -22.23 to -8.30), I2 88%; postprandial glucose -39.22 mg/dL; HbA1c WMD -0.56 (-0.99 to -0.13), I2 94%; HOMA-IR -0.76
   Certainty: Very high heterogeneity (I2 88-100%); HbA1c reported in the abstract with the unit mg/dL, which is a typo for percentage points; most participants also took diabetes drugs.
   Nutr Rev, 2025 · checked 2026-10-07 · we read the abstract
2. ev-cibs-02 · Meta-analysis or systematic review · updated systematic review and dose-response meta-analysis of randomized controlled trials · n = 24 trials
   Findings from 24 RCTs revealed that cinnamon supplementation had a statistically significant reduction in fasting blood sugar (SMD: -1.32; 95% CI: -1.77, -0.87, p < 0.001), Homeostatic Model Assessment for Insulin Resistance (SMD: -1.32; 95% CI: -1.77, -0.87, p < 0.001), and hemoglobin A1C (SMD: -0.67; 95% CI: -1.18, -0.15, p = 0.011) compared with the control group in patients with T2DM.
   
   Who: patients with type 2 diabetes in RCTs, searched to December 2022
   Effect: fasting blood sugar SMD -1.32 (95% CI -1.77 to -0.87); HbA1c SMD -0.67 (-1.18 to -0.15); insulin SMD -0.17 (-0.34 to 0.01), not significant
   Certainty: Largely the same trials as the 28-RCT review; standardized effects, no mg/dL in the abstract.
   Phytother Res, 2024 · checked 2026-10-07 · we read the abstract
3. ev-cibs-03 · Meta-analysis or systematic review · Cochrane systematic review of randomized controlled trials · n = 577
   There is insufficient evidence to support the use of cinnamon for type 1 or type 2 diabetes mellitus.
   
   Who: people with type 1 or type 2 diabetes in RCTs of oral cinnamon, mean 2 g a day for 4 to 16 weeks
   Effect: no significant difference in HbA1c, serum insulin or postprandial glucose; fasting glucose effect inconclusive
   Certainty: Search to January 2012; risk of bias high or unclear in 8 of 10 trials. Newer reviews pool more trials and reach a more positive answer.
   Cochrane Database of Systematic Reviews, 2012, Cinnamon for diabetes mellitus (CD007170) · checked 2026-10-07 · we read the abstract
4. ev-cibs-04 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 543
   No significant effect on hemoglobin A1c levels (-0.16%; 95%, CI -0.39% to 0.02%) was seen.
   
   Who: patients with type 2 diabetes, cinnamon 120 mg to 6 g a day for 4 to 18 weeks
   Effect: fasting plasma glucose -24.59 mg/dL (95% CI -40.52 to -8.67); HbA1c -0.16% (-0.39 to 0.02), not significant
   Certainty: I2 66.5% to 94.7%; dose and duration unclear.
   Annals of Family Medicine, 2013, 11(5):452-9, Cinnamon use in type 2 diabetes: an updated systematic review and meta-analysis · checked 2026-10-07 · we read the abstract
5. ev-cibs-05 · Meta-analysis or systematic review · meta-analysis of randomized placebo-controlled trials · n = 282
   Cinnamon does not appear to improve A1C, FBG, or lipid parameters in patients with type 1 or type 2 diabetes.
   
   Who: patients with type 1 or type 2 diabetes in randomized placebo-controlled trials
   Effect: no significant change in A1C, fasting blood glucose or lipids
   Certainty: Small and early; includes type 1 diabetes.
   Diabetes Care, 2008 · checked 2026-10-07 · we read the abstract
6. ev-cibs-06 · Meta-analysis or systematic review · systematic review and meta-analysis of clinical trials · n = 435
   Meta-analysis of RCTs showed a significant decrease in mean HbA1c [0.09%; 95% CI was 0.04-0.14] and mean FPG [0.84 mmol/l; 95% CI was 0.66-1.02].
   
   Who: patients with type 2 diabetes, 1 to 6 g a day for 40 days to 4 months
   Effect: HbA1c -0.09% (95% CI 0.04 to 0.14); fasting plasma glucose -15 mg/dL (12 to 18; metric: -0.84 mmol/L, 0.66 to 1.02)
   Certainty: An HbA1c fall of 0.09 points is far below what is clinically meaningful (about 0.3 to 0.5).
   Clin Nutr, 2012 · checked 2026-10-07 · we read the abstract
7. ev-cibs-07 · Meta-analysis or systematic review · umbrella review of meta-analyses of randomized controlled trials (AMSTAR 2) · n = 21 meta-analyses
   The findings indicate that cinnamon supplementation is significantly associated with improvements in fasting blood glucose and lipid profiles, with more pronounced effects observed in patients with diabetes and metabolic syndrome.
   
   Who: patients with metabolic diseases in meta-analyses of randomized placebo-controlled trials
   Effect: fasting glucose and lipids improved; stronger in diabetes and metabolic syndrome; doses above 1.5 g a day and 2 months or less looked better in subgroups
   Certainty: Overlapping reviews of the same small trials; no pooled number for glucose in the abstract.
   Frontiers in Nutrition, 2025, The effects of cinnamon on patients with metabolic diseases: an umbrella review of meta-analyses of randomized controlled trials · checked 2026-10-07 · we read the abstract
8. ev-cibs-08 · Meta-analysis or systematic review · GRADE-assessed systematic review, dose-response and meta-analysis of randomized controlled trials · n = 49 studies
   Cinnamon supplementation significantly reduced WC (SMD = - 0.40; 95% (CI): - 0.73, - 0.06), DBP (SMD = - 1.04; 95% CI: - 1.54, - 0.55), SBP (SMD = - 0.85; 95% CI: - 1.54, - 0.16), fasting glucose (SMD = - 1.28; 95% CI: - 1.65, - 0.90), fasting insulin (SMD = - 0.26; 95% CI: - 0.50, - 0.02), HbA1c (SMD = - 0.71; 95% CI: - 1.02, - 0.40), HOMA-IR (SMD = - 0.54; 95% CI: - 0.82, - 0.26), postprandial blood glucose (SMD = - 2.28; 95% CI: - 3.48, - 1.08), CRP (SMD = - 0.78; 95% CI: - 1.28, - 0.27), LDL-C (SMD = - 0.71; 95% CI: - 1.02, - 0.40), total cholesterol (TC) (SMD = - 1.15; 95% CI: - 1.55, - 0.75), triglycerides (TG) (SMD = - 0.91; 95% CI: - 1.25, - 0.56), and MDA (SMD = - 0.76; 95% CI: - 1.07, - 0.45).
   
   Who: adults in RCTs of cinnamon supplementation, searched to July 2024
   Effect: fasting glucose SMD -1.28 (95% CI -1.65 to -0.90); HbA1c SMD -0.71 (-1.02 to -0.40); postprandial glucose SMD -2.28 (-3.48 to -1.08)
   Certainty: Standardized effects of this size for a spice suggest heterogeneity and small-study effects; GRADE ratings not in the abstract.
   J Health Popul Nutr, 2025 · checked 2026-10-07 · we read the abstract
9. ev-cibs-09 · Meta-analysis or systematic review · systematic review and meta-analysis of randomized controlled trials · n = 5 trials
   After pooling data, cinnamon supplementation significantly reduced homeostatic model assessment for insulin resistance (HOMA-IR) scores in women with PCOS (SMD: -0.84, 95% CI: -1.52, -0.16, p = .010).
   
   Who: women with polycystic ovary syndrome in placebo-controlled RCTs
   Effect: HOMA-IR SMD -0.84 (95% CI -1.52 to -0.16)
   Certainty: Five small trials; HOMA-IR is a calculated index, not a clinical outcome.
   J Food Biochem, 2021 · checked 2026-10-07 · we read the abstract
10. ev-cibs-10 · Randomized controlled trial(s) · randomized controlled double-blind crossover trial (NCT04342624) · n = 18
    When compared with placebo, 24-h glucose concentrations were significantly lower when cinnamon was administered [mixed-models; effect size (ES) = 0.96; 95 % confidence interval (CI): -2.9, -1.5; P < 0.001].
    
    Who: participants with obesity and prediabetes, mean age 51.1 years, mean fasting glucose 102.9 mg/dL
    Effect: 24-hour glucose lower with cinnamon (effect size 0.96, 95% CI -2.9 to -1.5, P < 0.001); glucose peaks 9.56 vs 11.73 mg/dL
    Certainty: 18 people, 4 weeks, on a low-polyphenol diet run-in; the reported effect size and its interval do not match, so the absolute difference in 24-hour glucose cannot be read from the abstract.
    Am J Clin Nutr, 2024 · checked 2026-10-07 · we read the abstract
11. ev-cibs-11 · Randomized controlled trial(s) · randomized controlled double-blind crossover trial · n = 18
    No differences were found in digestive symptoms (abdominal pain, borborygmi, bloating, excess flatus, and stools/day) between cinnamon and placebo groups.
    
    Who: participants with obesity and prediabetes
    Effect: no difference in abdominal pain, borborygmi, bloating, flatus or stool frequency
    Certainty: Short trial; liver tests and coumarin exposure not reported in the abstract.
    Am J Clin Nutr, 2024 · checked 2026-10-07 · we read the abstract
12. ev-cibs-12 · Randomized controlled trial(s) · randomized placebo-controlled acute crossover trial · n = 10
    The peak BG concentration in response to the OGTT was significantly lower at the 30 min time point for CASS, as compared to PLC (140 ± 5.8 and 156 ± 5.2 mg/dL, p = .025); however, there was no significant difference between treatments for SI (p > .05).
    
    Who: young, sedentary, obese women
    Effect: peak glucose at 30 min 140 vs 156 mg/dL with placebo (p = .025); glucose and insulin area under the curve not different
    Certainty: Single dose in 10 people.
    J Diet Suppl, 2016 · checked 2026-10-07 · we read the abstract
13. ev-cibs-13 · Meta-analysis or systematic review · Cochrane systematic review of randomized controlled trials · n = 577
    Adverse reactions to oral cinnamon were infrequent and generally mild in nature.
    
    Who: people with diabetes in 10 RCTs of oral cinnamon
    Effect: adverse reactions infrequent and generally mild
    Certainty: Trials of 4 to 16 weeks cannot show slow harms such as liver injury from coumarin.
    Cochrane Database of Systematic Reviews, 2012, Cinnamon for diabetes mellitus (CD007170) · checked 2026-10-07 · we read the abstract
14. ev-cibs-14 · Position of an expert body · agency fact sheet · n = —
    It’s unclear whether cinnamon supplementation is helpful for diabetes or weight loss.
    
    Who: people considering cinnamon supplements
    Effect: benefit for diabetes unclear; higher quality research needed
    Certainty: Position without its own analysis.
    NCCIH, Cinnamon: Usefulness and Safety (fact sheet), last updated November 2024 · checked 2026-10-07 · we read the section
15. ev-cibs-15 · Position of an expert body · agency fact sheet · n = —
    Prolonged use of cassia cinnamon could be an issue for sensitive people, such as those with liver disease.
    
    Who: users of cassia cinnamon, especially people with liver disease
    Effect: coumarin-liver interactions reported; risk with high-coumarin cassia products and prolonged use
    Certainty: No dose threshold on the page; Ceylon cinnamon has only traces of coumarin.
    NCCIH, Cinnamon: Usefulness and Safety (fact sheet), last updated November 2024 · checked 2026-10-07 · we read the section
16. ev-cibs-16 · Position of an expert body · agency fact sheet · n = —
    If you take any type of medicine, talk with your health care provider before using cinnamon or other herbal products; some herbs and medicines interact in harmful ways.
    
    Who: people taking medicines, including diabetes drugs
    Effect: check with a health care provider before use
    Certainty: Interactions named in general terms only.
    NCCIH, Cinnamon: Usefulness and Safety (fact sheet), last updated November 2024 · checked 2026-10-07 · we read the section
17. cin-r2-03 · Randomized controlled trial(s) · four-way crossover controlled trial giving the same 12 mg dose of coumarin in four forms, isolated coumarin in a capsule as reference, cassia cinnamon in capsules, cinnamon tea and cinnamon in rice pudding, with relative absorption measured as urinary excretion of the metabolite 7-hydroxycoumarin over 8 hours and plasma levels over 105 minutes · n = 24
    The relative extent of absorption measured as urinary excretion of the main metabolite 7-hydroxycoumarin (7OHC) was found to be 62.8% for isolated coumarin in a capsule (reference), 56.0% for cinnamon in capsules, 66.1% for cinnamon tea, and 54.7% for cinnamon in rice pudding (means, n=23, observation period 8 hours).
    
    Who: 24 healthy volunteers, 23 analyzed
    Effect: relative absorption was 62.8% for isolated coumarin, 56.0% for cinnamon in capsules, 66.1% for cinnamon tea and 54.7% for cinnamon in rice pudding; tea gave the fastest absorption and the highest peak plasma concentration; the authors conclude the tolerable daily intake for coumarin can be applied to coumarin exposure from cinnamon-containing meals
    Certainty: 24 people, one dose, and a 2011 study, but it answers a question that is usually waved away rather than tested. What it does not do is tell you how much coumarin is in any particular jar: cassia carries up to about 1% and Ceylon cinnamon almost none, and shop labels rarely say which one it is. We do not publish the tolerable daily intake figure itself here because no source we could reach verified it
    Mol Nutr Food Res, 2011 · checked 2026-09-22 · we read the abstract
18. cin-r2-04 · Observational data · systematic review of human adverse event reports, Medline, Scopus, ScienceDirect, Embase, PubMed Central and Google Scholar searched for the terms cinnamon and cinnamomum across clinical trials, case reports and case series, plus spontaneous reports collected from five national and international reporting schemes · n = —
    The available data suggests that despite the safety of cinnamon use as a spice and/or flavoring agent, its use may be associated with significant adverse effects in medicinal uses with larger doses or longer duration of use and should be clinically monitored.
    
    Who: 38 clinical trials, 20 case reports, 7 case series and 160 spontaneous adverse event reports
    Effect: only 5 of the 38 clinical trials reported adverse events at all; the most frequent were gastrointestinal disorders and allergic reactions, self-limiting in the majority of cases
    Certainty: spontaneous reporting counts what somebody bothered to report, so this gives no rate and misses slow harms entirely. That 33 of 38 trials reported no adverse events is as likely to reflect trials not asking as cinnamon not causing. The distinction the authors draw between culinary and medicinal use is the line worth carrying, because the trials in this file all used the medicinal dose
    Clin Nutr, 2019 · checked 2026-09-22 · we read the abstract