Cinnamon Interactions

Cassia cinnamon contains coumarin, a natural compound with anticoagulant activity that may potentiate warfarin and increase bleeding risk. Case reports describe elevated INR and bleeding when cinnamon supplements were added to stable warfarin therapy.

Cinnamon (particularly cassia and ceylon varieties) has a mild antiglycemic effect that can produce an additive blood sugar reduction when combined with metformin. The effect is modest in most studies but can become clinically meaningful in patients with already well-controlled A1c or those on combination diabetes regimens.