Supplement
Cinnamon (Cassia / Ceylon)
Fasting glucose and some lipid markers in type 2 diabetes; the effect is modest and HbA1c A blood test that reflects average blood sugar over the previous two to three months. results are less consistent.
Cinnamon is a common spice sold in two main types, cassia and Ceylon. In people with type 2 diabetes, pooled studies found modest drops in fasting blood sugar and some blood fats. Results for long-term blood sugar were less consistent. Most studies used cassia, which contains a compound called coumarin. Ceylon has very little. Coumarin is a concern in liver disease, and cinnamon can add to diabetes drugs and push blood sugar too low.
- Dose studied
- 2–6 g/day
- Form graded
- Cassia or Ceylon cinnamon (aqueous/whole)
- Cited PMIDs PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed.
- PMID 24019277 →PMID 38917435 →
A letter describes the human evidence, not the product, the manufacturer, or the ingredient's worth.
See the full evidence record →Who responds: this record's trial reading reports no subgroup that identifies who responds.
Cinnamon (Cassia / Ceylon) for fasting glucose and HbA1c, graded on published human trial evidence.
A grade describes the intervention that was tested. Where the product on the shelf differs from it, this says so.
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No dose is published here. This record carries no authored dose, because the cited trials do not converge on a single figure. Each trial cited on this page states the dose it used, and EBL has not turned those into a recommendation.
Standardized extracts/forms were used in the cited trials; product quality varies.
The cited reviews pool trials and do not report when doses were taken (PMID 24019277, PMID 38917435).
Checked against the published summaries; the full papers could not be read. What the cited trials did, not a schedule. Every supplement, by trial timing →
Liver disease, and any situation where cumulative coumarin intake matters. Cassia cinnamon, which is what most supplements and most kitchens contain, carries coumarin; Ceylon cinnamon carries very little. The two are sold under the same word.
Diabetes medication, including insulin, sulfonylureas and metformin: cinnamon lowers fasting glucose in pooled trial evidence, so the effect is additive and hypoglycemia is the failure mode. Anticoagulants: coumarin is not warfarin, but cassia's coumarin load is a reason to be deliberate about the combination.
Cassia cinnamon carries coumarin; Ceylon does not. Cassia cinnamon contains coumarin at levels that make cumulative intake a liver-safety question, and most cinnamon sold as a supplement or a spice is cassia. Abraham et al. (Molecular Nutrition and Food Research, 2010; PMID 20024932): toxicology and risk assessment of coumarin, focused on the human data.
Fasting blood glucose and HbA1c at baseline and 12 weeks: the glucose-lowering evidence is the most replicated The same finding reproduced by a separate research group. A result seen once can be chance or bias; a replicated one is harder to explain away. in human trials. Also monitor fasting insulin and HOMA-IR if available. Cassia cinnamon contains coumarin and should not be used at high doses long-term: Ceylon cinnamon is the safer choice for sustained use, though most trials used Cassia.
Primary evidenceTwo papers, each linked to its PubMed record.
Allen et al. (Annals of Family Medicine, 2013; PMID 24019277) and de Moura et al. (Nutrition Reviews, 2025; PMID 38917435): meta-analyses: cinnamon modestly lowered fasting glucose and some lipid markers in type 2 diabetes; HbA1c effects were less consistent. Grade B: meta-analytic RCT Randomized controlled trial: people are assigned to the treatment or a comparison by chance, so the groups differ only in what they received. It is the design that can show cause and effect. evidence, modest glycemic effect.
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