Adults

For prevention of Vitamin D deficiency: 1000 IU (1 tablet) daily. For treatment of established deficiency, higher doses may be prescribed by a physician.

Elderly

Same as adults, but monitoring may be required, especially if there's reduced renal function.

Renal_impairment

Use with caution and monitor calcium and phosphate levels. Different forms of Vitamin D may be required in severe renal impairment.

Onset

Clinical effects may take weeks to months to become apparent, as stored vitamin D is gradually converted to its active form.

Excretion

Mainly excreted in bile and feces, with a small amount excreted renally.

Half life

The elimination half-life of 25-hydroxyvitamin D (calcidiol) in circulation is approximately 15-30 days.

Absorption

Well absorbed from the small intestine, primarily in the jejunum, in the presence of bile salts and dietary fat.

Metabolism

Initially hydroxylated in the liver to 25-hydroxycholecalciferol (calcidiol), then further hydroxylated in the kidneys to 1,25-dihydroxycholecalciferol (calcitriol), the active form.

Corticosteroids

May counteract the effects of vitamin D.

Thiazide diuretics

May increase the risk of hypercalcemia.

Cholestyramine, Colestipol, Orlistat, Mineral oil

May reduce the intestinal absorption of vitamin D.

Antiepileptic drugs (e.g., phenytoin, barbiturates)

May increase vitamin D metabolism, leading to reduced efficacy.