mgtounits

600 IU of vitamin D to mg and mcg

600 IU of vitamin D = 15 mcg = 0.015 mg. Vitamin D has 40 IU per microgram, so divide IU by 40 to get mcg and by 40,000 to get mg.

600 IU=15 mcg=0.015 mg

How the conversion works

mcg = IU ÷ 40 → 600 ÷ 40 = 15 mcg mg = mcg ÷ 1,000 → 15 ÷ 1,000 = 0.015 mg

The factor comes from the NIH Office of Dietary Supplements: 1 mcg of vitamin D (cholecalciferol, D3, or ergocalciferol, D2) has 40 IU of activity. It works backwards too: 15 mcg × 40 = 600 IU.

Where you'll see 600 IU

600 IU is the RDA for people aged 1 to 70 (15 mcg), including during pregnancy and breastfeeding. Since the FDA's label rules changed (compliance from 2020–2021), supplement labels show vitamin D in mcg, often with IU in brackets: look for 15 mcg (600 IU).

This page converts units; it doesn't recommend a dose. NIH sets the adult upper limit at 4,000 IU (100 mcg) a day. Talk to your clinician about what's right for you.

Convert another amount

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Nearby doses

See every common strength in the vitamin D IU to mcg table, or convert vitamin E, A and insulin with the IU to mg converter.

Questions

Is 600 IU the same as 15 mcg?

Yes, for vitamin D (D3 or D2). 600 ÷ 40 = 15 mcg. US labels now list mcg first, for example "15 mcg (600 IU)".

How many mg is 600 IU of vitamin D?

0.015 mg. One milligram is 1,000 mcg, so 15 mcg ÷ 1,000 = 0.015 mg.

Does 600 IU convert the same way for other vitamins?

No. An IU measures biological activity, so every substance has its own factor. 400 IU of vitamin E is about 268 mg (natural) or 180 mg (synthetic), not 0.01 mg. Use the IU to mg converter and pick the substance.