The patients allocated to the intervention group will have a test for serum vitamin D, and receive 800 IU of vitamin D and 1000 mg of calcium as calcium carbonate when the serum vitamin D is decreased. The patients in the control group will be followed up without intervention for one year.

The intervention group will receive tablets containing 400IU cholecalciferol and 500mg of elemental calcium as calcium carbonate twice daily (CAVID CHEWABLE TAB, Takeda Pharmaceuticals) for 12 months when the initial serum vitamin D is decreased. The compliance will be determined by the percentage of consumed tablets from the delivered tablets during the follow-up period. Discontinuation of the supplementation due to adverse effects or other reasons will be registered using the telephone interview together with the primary outcome date. Participants in the control group will not have any intervention or placebo. They will not be allowed to take vitamin D or calcium as supplements during the follow-up. The primary outcome measure is the recurrence of BPPV after one year. Data on recurrences will be collected using a monthly telephone interview, and the patients will be asked to visit the clinic whenever they have the symptoms of BPPV. All the recurrences of BPPV will be included.

In intervention group, the baseline vitamin D status of participants will be checked. And the level of 25-hydroxyvitamin D level will be rechecked at 2 months from the recruitment and at the end of the follow-up.