What is the equivalent of 20 micrograms (mcg) of vitamin D in International Units (IU)?

Vitamin D Conversion: Micrograms to International Units

20 micrograms (mcg) of vitamin D is equivalent to 800 International Units (IU). 1

Conversion Factor

• The standard conversion factor for vitamin D is 1 mcg = 40 IU 1
• Therefore, 20 mcg × 40 = 800 IU 1

Clinical Context

• 800 IU/day is the recommended daily allowance for vitamin D in individuals over 60 years 2
• For younger adults, 400 IU/day is the standard recommendation 2
• 800 IU/day is also the recommended dose for dark-skinned or veiled individuals with limited sun exposure, without requiring baseline testing 2, 1

Supplementation Guidelines

• Daily doses of 600-800 IU are generally recommended for adults for maintenance 1
• Higher doses of 1500-4000 IU daily are recommended for patients at risk for vitamin D deficiency 1
• As a rule of thumb, 1,000 IU of vitamin D daily increases serum 25(OH)D by approximately 10 ng/mL 1

Safety Considerations

• Most international authorities consider 2,000 IU daily as absolutely safe 1
• The general upper daily limit for vitamin D intake is 4,000 IU 1
• Doses up to 10,000 IU per day supplemented over several months have not led to adverse events in studies 1
• Hypercalcemia due to vitamin D toxicity generally occurs only when daily intake exceeds 100,000 IU 1

Monitoring Recommendations

• The optimal target range for serum 25(OH)D is 30-80 ng/mL for health benefits 1, 3
• Wait at least 3 months after starting supplementation before measuring 25(OH)D levels to assess response 1, 3
• The upper safety limit for serum 25(OH)D levels is 100 ng/mL 1, 3