Across 3 studies, 2 reported beneficial effects of cinnamon on reducing Hemoglobin A1c, while 1 found no significant effect. The predominant effect size was small, with one meta-analysis reporting a 0.10% reduction (small) and another showing a moderate effect (SMD -0.71). The evidence base is small, and the most-studied population is adults with type 2 diabetes, though doses and durations were not consistently reported.

• Studied populations: adults with type 2 diabetes

Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Study durations were not consistently reported, so the time course of effects is unclear. The neutral study (a 2024 meta-analysis) did not find significant improvement in HbA1c from cinnamon specifically, contrasting with the two beneficial studies — this inconsistency warrants caution. No form data were extracted, so it is unknown whether specific cinnamon preparations (e.g., cassia vs. Ceylon) drive the effects.