Background: Supplementation of vitamin D2 or vitamin D3 is recommended for vitamin D deficiency. Weekly supplementation of 60,000 IU of vitamin D3 increases serum 25(OH) D to optimal values. Various marketed forms of vitamin D3 include tablets, capsule, granules and oral solution. The main objective of this study is to compare the relative bioavailability of vitamin D3 oral solution with vitamin D3 tablet and capsule.Methods: This is an open-label, randomized, single-dose, three-treatment study to compare the relative bioavailability of vitamin D3 oral solution with capsule and tablet. Subjects (n=70) were supplemented with single dose of one of these formulations and their blood sample were assessed for Cmax, AUC0-28d and Tmax.Results: The logarithmic transformed data of pharmacokinetic parameters were analyzed for 90% Confidence Intervals (CI) using ANOVA. The mean (90% CI) values of vitamin D3 oral solution against tablet for the ratio of Cmax and AUC0-28d were 113.00 (105.32-121.23) and 105.54 (97.95-113.72) respectively. The mean (90% CI) values of vitamin D3 oral solution against capsule for the ratio of Cmax and AUC0-28d were 115.02 (106.38 - 124.37) and 112.33 (104.44 - 120.81) respectively. These values were within the bioequivalence range of 80-125%.Conclusions: It is concluded that vitamin D3 Oral Solution formulated with nanotechnology is bioequivalent to vitamin D3 tablet and capsule. However, oral solution of vitamin D3 shows higher Cmax and AUC when compared to tablet and capsule formulations.