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Moderate evidenceHeart & metabolic

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.

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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

Studied doseTrials used 1–6 g/day of cinnamon powder, most commonly 1–3 g/day taken with meals for 8–16 weeks.
SafetyCassia is rich in coumarin, which is hepatotoxic at high chronic intakes; people with liver disease or on hepatotoxic drugs should prefer Ceylon cinnamon or low-coumarin extracts. May add to the effect of glucose-lowering medication.

How to take it

TimingTake it with meals, which is when it can blunt the post-meal glucose rise.
With food?With food; the trials dosed it alongside meals.
Worth knowingIf you plan to take grams of it every day for months, switch to Ceylon cinnamon, which carries a fraction of the coumarin.

Interactions

With medications

  • insulin, sulfonylureas, metformin and other glucose-lowering drugs

    Additive blood glucose lowering. monitor your glucose and tell your doctor you are taking it

  • medication that stresses the liver, such as methotrexate or isoniazid

    Cassia is high in coumarin, which is hepatotoxic at sustained high intakes. use Ceylon cinnamon or a low-coumarin extract instead

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does cinnamon lower blood sugar?

Cassia cinnamon has moderate evidence for a small drop in fasting glucose in type 2 diabetes, with most of the effect around 2 g/day. The effect on HbA1c, the long-term marker, is unclear, and trials disagree.

How much cassia cinnamon is safe per day?

Cassia cinnamon is rich in coumarin, and a few grams per day can exceed the tolerable daily intake for an adult. If you take grams of cinnamon daily for months, switch to Ceylon cinnamon, which contains far less coumarin.

How much cinnamon should I take for blood sugar?

Cinnamon trials used 1–6 g/day of powder, most commonly 1–3 g/day taken with meals for 8–16 weeks. Cassia cinnamon's coumarin content is the practical limit on how much you can safely take.

Can I take cinnamon with diabetes medication?

Cassia cinnamon can add to the glucose-lowering effect of insulin, sulfonylureas and metformin, so monitor your glucose and tell your doctor. With liver disease or drugs that stress the liver, such as methotrexate, use Ceylon cinnamon or a low-coumarin extract instead.

Scientific references

Related in Heart & metabolic

Herbal medicines: what the evidence says (335)