Objective: Vitamin- D deficiency is very common and various modalities are suggested to treat the same. Annual Single dose of Vitamin-D is one of the few options tested by some authors. Here we present reports of our Annual Single Mega-dose of Vitamin-D injection as Supplementation Therapy. Type of study-This was a prospective interventional study. Design: This was open, uncontrolled dose finding design. Participants- 18 Women participated in study. Vitamin-D Doses- All these participants received one single mega-dose of 600,000 IU by intramuscular route. Final blood sampling was done one year after the mega-dose. Results: All those with Vitamin-D levels more than or equal to 50 nanograms/ml in Last/ final sampling were grouped as ‘YES’ response candidates. Out of 18 participants; 11/18 or 62% showed Vitamin-D levels more than 50nanograms/ml. Both groups were at par in terms of all parameters like Base line Hemoglobin and Vitamin-D levels, BMI, Age and Parity. Conclusion: In our series all participants of Indian Ethnicity had good vitamin-d levels to start with but one single megs-dose failed to maintain it for one year in all subjects again pointing to prominent role of genetic factors in Calcium and Vitamin-D metabolism.