Inclusion Criteria:  Women aged 20 to 42 years old; Diagnosed with PCOS (Rotterdam Criteria); Written informed consent.  Exclusion Criteria:  Non-PCOS Infertile patients, e.g, who have Cushing's syndrome, congenital adrenal hyperplasia, androgen-secreting tumors, hyperprolactinemia. PCOS patients who are underwent any anti-infertility treatments. PCOS patients who had receiving any vitamin D supplement or any multivitamin supplement within the past 3 month prior to enrollment process. PCOS patients with established diagnosis of diabetes mellitus, chronic liver, kidney, or thyroid diseases. PCOS patients receiving any treatment affect the metabolism of vitamin D. Any supplements that contain vitamin D within the past month.