Vitamin D: What the Label Numbers Mean
How to read vitamin D amounts on a Supplement Facts panel, the IU-to-mcg conversion, and why %DV matters.
Vitamin D on a Supplement Facts panel is listed in both micrograms (mcg) and International Units (IU). The conversion is straightforward: 1 mcg of vitamin D equals 40 IU, so a 25 mcg serving is 1,000 IU.
The percent Daily Value (%DV) is based on a reference intake of 20 mcg (800 IU) for adults. A label showing 25 mcg therefore lists 125% DV. Amounts above 100% DV are common in single-nutrient products and are not unusual.
Vitamin D appears on labels as either D2 (ergocalciferol) or D3 (cholecalciferol). Both raise blood levels, though research generally finds D3 more effective at maintaining them. Always follow the dose printed on the label and talk to a healthcare provider before taking high-dose products.
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This article is for general educational purposes only and is not medical advice or a product endorsement. Always follow the printed product label and consult a qualified healthcare provider.