Higher dose of vitamin D supplementation 50000 IU is required for those whose serum 25(OH)D levels are 50 nmol/L and below. The increment in serum 25(OH)D though not significantly affected by race, sex or age it is negatively correlated to the baseline 25(OH)D concentration. This study investigated whether the mean increase in serum 25(OH)D will be higher among participants with lower baseline 25(OH)D levels and whether the duration of supplementation has an influence on the serum 25(OH)D achieved.

A clinical audit of patients' medical records from a community health centre in Melbourne for the period 01.01.2010 to 31-12.2012 was undertaken. Paired sample t test was used to determine difference in pre and post dose serum 25(OH)D. Simple and multiple linear regressions were used to examine the association between the difference in pre and post dose serum 25(OH)D and duration of supplementation and baseline serum 25(OH)D, adjusting for socio-demographic factors.

 = 6.11, p < 0.05) and there was an inverse relationship between the length of supplementation and mean pre and post supplementation serum 25(OH)D difference (β = -1.45, 95 % CI: -2.62, -0.29, p = 0.014).

Following 50000 IU vitamin D3 for 12 months mean serum 25(OH)D increase was highest among those whose baseline serum 25(OH)D was lower. Migrants especially dark-skinned are at a high risk for vitamin D deficiency in Australia. High dose vitamin D3 50000 IU (cholecalciferol) is effective in achieving sufficient serum 25(OH)D among these populations who tend to have lower baseline serum 25(OH)D.