AbstractPremenstrual syndrome (PMS) and primary dysmenorrhea are common gynecological problems and inflammation may have a role in their etiology. Curcumin is a polyphenolic natural product for which there is increasing evidence of anti‐inflammatory and iron chelation effects. This study assessed the effects of curcumin on inflammatory biomarkers and iron profile in young women with PMS and dysmenorrhea. A sample of 76 patients was included in this triple‐blind, placebo‐controlled clinical trial. Participants were randomly allocated to curcumin (n= 38) and control groups (n= 38). Each participant received one capsule (500 mg of curcuminoid+ piperine, or placebo) daily, from 7 days before until 3 days after menstruation for three consecutive menstrual cycles. Serum iron, ferritin, total iron‐binding capacity (TIBC) and high‐sensitivity C‐reactive protein (hsCRP), as well as white blood cell, lymphocyte, neutrophil, platelet counts, mean platelet volume (MPV) and red blood cell distribution width (RDW), were quantified. Neutrophil: lymphocyte ratio (NLR), platelet: lymphocyte ratio (PLR), and RDW: platelet ratio (RPR) were also calculated. Curcumin significantly decreased the median (interquartile range) serum levels of hsCRP [from 0.30 mg/L (0.0–1.10) to 0.20 mg/L (0.0–1.3);p= 0.041] compared with placebo, but did not show any difference for neutrophil, RDW, MPV, NLR, PLR and RPR values (p> 0.05). The treatment schedule was well‐tolerated, and none of markers of iron metabolism statistically changed after the intervention in the curcumin group (p> 0.05). Curcumin supplementation may have positive effects on serum hsCRP, a marker of inflammation, with no any changes on iron homeostasis in healthy women with PMS and dysmenorrhea.