50,000 IU of vitamin D to mg and mcg

50,000 IU of vitamin D = 1,250 mcg = 1.25 mg. Vitamin D has 40 IU per microgram, so divide IU by 40 to get mcg and by 40,000 to get mg.

How the conversion works

mcg = IU ÷ 40 → 50,000 ÷ 40 = 1,250 mcg mg = mcg ÷ 1,000 → 1,250 ÷ 1,000 = 1.25 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: 1,250 mcg × 40 = 50,000 IU.

Where you'll see 50,000 IU

50,000 IU is a prescription strength (ergocalciferol 1.25 mg capsules). It's usually taken once a week or less often, under a prescriber's direction, never daily on your own. 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 1,250 mcg (50,000 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

Nearby doses

• 2,000 IU to mg = 50 mcg
• 5,000 IU to mg = 125 mcg

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.