An oral dosage form comprising a single dose of 25-hydroxy-vitamin D3 sufficient to elevate the serum level in a human to a concentration in the range of 30 ng/ml to 200 ng/ml for at least 7 days and a pharmaceutically suitable oral carrier system, wherein subsequent single doses at least every 7 days are sufficient to sustain the serum level in a human to a concentration in the range of 30 ng/ml to 200 ng/ml at steady-state pharmacokinetics is disclosed. A method of elevating and sustaining the blood level concentration of 25-hydroxy-vitamin D3 in a human in need thereof comprising orally administering or parenterally administering by injection or infusion, at least once every 7 days, a single dose of 25-hydroxy-vitamin D3 sufficient to elevate the serum level in a human to a concentration in the range of 30 ng/ml to 200 ng/ml for at least 7 days, wherein the single doses orally administered at least every 7 days are sufficient to sustain the serum level in a human to a concentration in the range of 30 ng/ml to 200 ng/ml at steady-state pharmacokinetics is disclosed. The human in need thereof may be a human deficient in vitamin D having a serum level concentration of 25-hydroxy-vitamin D3 less than 30 ng/ml.
