I am low on Vit.D3, less than 4, was given 600,000 IU and level came to 29. Now on D3 I was ow on Vit.D3, was less than 4 ng/ml 3 months back, was given 600,000 IU Archacitol injection, and level came to 29. Now on D3 saches (60,000 IU) once every 15 days. Still sometimes feel muscle weakness and bone joint pains. Age: 50, Height: 5 7 , weight:110 kgs. should frequency of taking D3 sache be increased. How frequently should I check Vit.D3 level through blood sample.