Cassia Cinnamon
The common supermarket cinnamon, sold standardised for blood sugar. Meta-analyses show a small drop in fasting glucose in type 2 diabetes with inconsistent effects on HbA1c, and its coumarin content limits how much you can safely take.
Evidence last reviewed: August 2026
What the science says
- Small reduction in fasting glucose Moderate evidence
An updated dose-response meta-analysis of randomised controlled trials in type 2 diabetes found cinnamon lowered fasting blood glucose, with most of the effect at intakes around 2 g/day. Individual trials disagree and the pooled estimate carries high heterogeneity.
- Unclear effect on HbA1c Limited evidence
An earlier meta-analysis of randomised trials found improvements in fasting glucose and lipids but no significant change in HbA1c, the marker that reflects longer-term glycemic control.
- Coumarin content is the practical limit Moderate evidence
Analytical work on retail cassia bark found coumarin levels high enough that a few grams per day can exceed the tolerable daily intake for an adult. Ceylon cinnamon contains far less.
Dosage & safety
Scientific references
- 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
- Cinnamon use in type 2 diabetes: an updated systematic review and meta-analysis
- Quantification of flavoring constituents in cinnamon: high variation of coumarin in cassia bark from the German retail market and in authentic samples from indonesia
Where to buy
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Related in Heart & metabolic
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