Introduction Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in reproductive-age women. Chinese herbal medicine has been used for the treatment of PCOS, but the evidence for its efficacy and safety is minimal. Tanshinones are a class of bioactive molecules isolated from Salvia miltiorrhiza, a commonly used herb in Traditional Chinese Medicine. This study aims to evaluate the efficacy of tanshinones on hyperandrogenism and quality of life in women with PCOS who do not attempt to conceive.

Methods and analysis A total of 100 patients will be recruited and randomised into the tanshinone or placebo group. Tanshinone or placebo capsules will be taken orally for 12 weeks. The primary outcome parameter will be a change in plasma testosterone. Secondary end points will be changes in human chorionic gonadotropin-induced androgen response, insulin resistance, reproductive hormones, fasting lipid profiles, oral glucose tolerance test, quality of life and side effects.

Ethics and dissemination Written informed consent will be obtained from each participant at the time of enrolling in the study. The trial has been approved by the Ethics Committee of First Affiliated Hospital of Heilongjiang University of Chinese Medicine. Results will be disseminated through a publicly accessible website.

Registration details The study has been registered at the Chinese Clinical Trials Registry (ChiCTR-TRC-12002973) and at clinicaltrials.gov (NCT 01452477).