Cinnamon

Cinnamomum cassia · Cinnamomum verum · Cinnamomum zeylanicum · Cinnamaldehyde

Snapshot

Indications	Contraindications
Glycemic control in type 2 diabetes^{1, 2} Prediabetes glucose response^{3, 4} Polycystic ovary syndrome^5–9 Metabolic syndrome^{10, 11} Blood lipid profile^12–16	Pregnancy or nursing¹⁷ Cinnamon or Peru balsam allergy¹⁸ Statin co-use¹⁹

Cinnamon is the dried bark of Cinnamomum trees, sold mainly as Ceylon (Cinnamomum verum) or cassia, and products often do not state which²⁰. It is taken for its effect on insulin signaling and glucose handling²¹. The uses that follow are glycemic control in type 2 diabetes and prediabetes, insulin resistance in polycystic ovary syndrome, and lipid and weight measures in metabolic syndrome. Adults with type 2 diabetes are among the most frequent herbal users²².

Meta-analyses of randomized trials in type 2 diabetes found lower fasting glucose, hemoglobin A1c, and insulin resistance, with high heterogeneity^{1, 2}. A separate trial in type 2 diabetes found no effect on glycemic indicators²³, and the National Center for Complementary and Integrative Health (NCCIH) states that research does not clearly support cinnamon for any health condition²⁰. In laboratory models, a 2026 study found cinnamon bud extract and cinnamaldehyde inhibited tau aggregate maturation, and no human trial has tested this. Capsules dominate the products listing cinnamon, and species and extract type differ; see Form comparison.

Cassia products can carry high coumarin, the proposed basis for rare liver injury, which LiverTox rates as a possible rare cause of clinically apparent liver injury²⁴. Per NCCIH, people taking any medicine are asked to talk with their health care provider before using herbal products²⁰.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

71 sources, 61 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources