Microgram ↔ IU Conversion
Select a nutrient to convert between weight-based dosing (micrograms) and biological activity (International Units). Reference data follows NIH dietary supplement guidance.
Used for bone health and immune modulation. 1 mcg = 40 IU.
Conversion Result
Vitamin D₃ (cholecalciferol)
25 mcg = 1,000 IU
Conversion factor: 1 mcg = 40 IU.
Source: US NIH Office of Dietary Supplements
Instructions
Select the vitamin form
Different nutrients use unique IU definitions. Choose the correct vitamin form (e.g., vitamin D₃).
Enter the amount and units
Convert supplement labels (often in IU) or prescription orders (commonly mcg or mg).
Apply clinically
Use the converted value to verify dosing, compare products, or counsel patients on intake.
Formula
IU = mcg × IU per microgram
mcg = IU ÷ IU per microgram
Conversion factors differ by nutrient and sometimes by chemical form (natural vs synthetic).
Frequently Asked Questions
What does the mcg to IU Converter do?
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Is the mcg to IU Converter a substitute for professional advice?
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