The purpose of this study is to evaluate the effect of vitamin D supplementation on the pain score of primary dysmenorrhea. Our hypothesis is that by normalizing vitamin D level could help improve pain score of women who have primary dysmenorrhea.

This study is aimed to be conducted in randomised controlled trial, comparing between intervention group and placebo group. We include women with primary dysmenorrhea who also have low vitamin D level in this trial. Our primary outcome is to compare visual analog pain scale between intervention and placebo group after treatment. After randomised and allocated, these women will be given vitamin D 50,000 IU or placebo capsules orally weekly for 8 consecutive weeks. We monitor pain score daily from the cycle before the drugs started until complete 8-week course of the regimen mentioned. Also vitamin D levels will be monitored twice, one before treatment and the other after treatment.

Inclusion Criteria:

• Primary dysmenorrhea
• Hypovitaminosis D

Exclusion Criteria:

• Using calcium, magnesium or phosphorus in the past 3 months
• Using hormonal contraception or IUD in the past 6 months
• No smoking or alcohol drinking
• Chronic underlying diseases
• Allergic to components in study drugs