What is the recommended daily intake of vitamin D (International Units) during pregnancy?

Vitamin D Supplementation During Pregnancy

Pregnant women should take at least 1,000 IU (40 mcg) of vitamin D daily, with a target of maintaining serum 25-hydroxyvitamin D levels above 50 nmol/L (20 ng/mL). 1

Standard Dosing Recommendations

The evidence supports the following approach:

• Minimum daily dose: 1,000 IU (40 mcg/day) for all pregnant women to maintain adequate vitamin D status 1
• General adult recommendation: 600-800 IU daily is the baseline for non-pregnant adults, but this is insufficient for pregnancy 2
• Upper safety limit: 4,000 IU daily for all adults including pregnant women 2

Evidence-Based Dosing Strategy

The most recent and highest quality evidence demonstrates that standard low-dose supplementation is inadequate:

• 1,000 IU daily is minimally effective: A 2024 prospective cohort study found that 1,000 IU supplementation had limited clinical effectiveness, with 67% of deficient women remaining deficient after 16 weeks of supplementation 3
• 2,000 IU daily is more effective: A 2014 randomized controlled trial comparing 600,1,200, and 2,000 IU daily found that only the 2,000 IU dose achieved adequate vitamin D sufficiency in 80% of mothers (versus 42% with 600 IU and 39% with 1,200 IU) 4
• Higher doses may be necessary: The Endocrine Society recommends 1,500-2,000 IU daily for pregnant women with vitamin D deficiency, noting that 600 IU may be insufficient 5

Special Population Considerations

Women with obesity (BMI >30 kg/m²):

• Require the same vitamin D dose (minimum 1,000 IU) but need concurrent higher folic acid supplementation (4-5 mg daily versus standard 0.4 mg) 2

Women after bariatric surgery:

• Require higher doses: minimum 1,000 IU (40 mcg) daily 2
• Need more intensive monitoring every trimester 2
• Should maintain serum 25-hydroxyvitamin D ≥50 nmol/L with PTH within normal limits 2

Women with cystic fibrosis:

• Should take an additional 600 IU (15 mcg) per day during pregnancy on top of their baseline supplementation 2

Monitoring Protocol

Baseline assessment:

• Check serum 25-hydroxyvitamin D before conception or early in pregnancy 2
• Measure calcium, phosphate, magnesium, and PTH alongside vitamin D 2

During pregnancy:

• Monitor at least once per trimester using pregnancy-specific reference ranges 2
• Recheck 3-6 months after any dose adjustment 2
• Target serum level: ≥50 nmol/L (20 ng/mL) 1

Critical Pitfalls to Avoid

Do not rely on 600 IU daily as adequate supplementation: While this is the Institute of Medicine recommendation, recent evidence shows it is insufficient for many pregnant women, particularly those at high risk for deficiency 5, 3

Do not assume dietary intake is sufficient: Vitamin D from food sources (fatty fish, eggs, fortified products) typically does not meet pregnancy requirements 2

Do not delay supplementation: Begin at least 2-3 months before planned conception to optimize vitamin D stores 1

Use vitamin D₃ (cholecalciferol), not D₂ (ergocalciferol): D₃ is more effective at raising and maintaining serum levels 1

Practical Implementation

For most pregnant women without special risk factors:

• Start with 1,000-2,000 IU daily based on baseline vitamin D status 1, 4
• Add calcium supplementation (1,200-1,500 mg daily in divided doses) if needed to maintain PTH within normal limits 2
• Monitor response with serum testing each trimester 2
• Adjust dose upward if serum 25-hydroxyvitamin D remains <50 nmol/L 1

The divergence between older guidelines (600 IU) and newer evidence (1,000-2,000 IU) reflects growing recognition that vitamin D deficiency affects 40-57% of pregnant women and that higher doses are necessary to achieve sufficiency 2, 3.