Vitamin D3

What it is

Vitamin D3 (cholecalciferol) is a fat-soluble vitamin and prohormone produced in skin from sunlight and obtained from a few foods and supplements. It regulates calcium and phosphate absorption, making it essential for bone mineralization, and also influences immune and muscle function.

Benefits

Supplementation corrects deficiency and supports bone health, with the clearest benefit in people with low blood levels. Common supplemental doses range from 1,000-4,000 IU per day; 4,000 IU is the established tolerable upper intake level for adults, and higher therapeutic doses should be guided by blood testing.

When to take it

Taken daily with a meal containing fat to aid absorption; deficient individuals may need higher repletion doses temporarily under clinical guidance.

Side effects

Toxicity is rare but possible with chronic high supplemental intake, causing hypercalcemia (nausea, weakness, kidney issues). Deficiency is common in people with limited sun exposure, darker skin, or obesity, so dosing is best matched to measured 25(OH)D levels.

Sources

• NIH ODS Vitamin D Fact Sheet for Health Professionals

Products containing Vitamin D3

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