Converting Vitamin D from Micrograms to International Units
20 micrograms (µg) of vitamin D equals 800 International Units (IU), as the conversion factor is 1 µg = 40 IU. 1, 2
Conversion Formula and Calculation
The conversion between micrograms and International Units for vitamin D follows a simple formula:
- 1 microgram (µg) of vitamin D = 40 International Units (IU)
- Therefore: 20 µg × 40 = 800 IU
This conversion factor is consistently used across clinical guidelines and research literature when discussing vitamin D supplementation and dosing.
Context in Clinical Practice
Understanding this conversion is important in clinical practice because:
- Vitamin D recommendations and dosages are often expressed in different units depending on the source
- Dietary guidelines typically use both µg and IU
- Supplement labels may use either measurement system
According to the British Journal of Sports Medicine, the average daily intake of vitamin D across the world is approximately 100-250 IU (2.5-6.25 µg), which is less than the current Recommended Dietary Allowance (RDA) of:
- 400 IU in the UK
- 600 IU in North America 1
Recommended Daily Intake
For reference, current vitamin D intake recommendations from guidelines include:
- Adults aged 19-70 years: 15 µg (600 IU) daily
- Adults over 70 years: 20 µg (800 IU) daily
- Special populations (dark-skinned individuals, elderly, institutionalized): 800 IU daily 2
Common Pitfalls
When working with vitamin D measurements, be aware of these potential errors:
- Confusing µg and mg (1 mg = 1000 µg)
- Incorrectly applying the conversion factor (the correct factor is 40, not 4 or 400)
- Failing to note which form of measurement is being used in clinical recommendations
This conversion knowledge is essential when interpreting research findings, prescribing supplements, or educating patients about vitamin D requirements and supplementation.