What is the best form of vitamin D (Vitamin D) to take?

Best Form of Vitamin D to Take

Cholecalciferol (Vitamin D3) is the superior form of vitamin D for supplementation and should be used preferentially over ergocalciferol (Vitamin D2) for both treatment and maintenance therapy. 1, 2, 3, 4

Why Vitamin D3 is Superior to Vitamin D2

Vitamin D3 demonstrates significantly greater potency and longer duration of action compared to Vitamin D2. The evidence supporting D3's superiority is compelling:

• Vitamin D3 maintains serum 25(OH)D concentrations for substantially longer periods than D2, particularly when using intermittent dosing schedules (weekly or monthly). 2, 3
• D3 is more stable during storage and far less susceptible to breakdown during cooking and baking compared to D2. 3
• D3 has proven to be the more potent form in all primate species, including humans, when measured by objective 25-hydroxyvitamin D levels. 4
• D2 metabolites have diminished binding to vitamin D binding protein in plasma and undergo nonphysiologic metabolism with a shorter shelf life. 4

Practical Dosing Recommendations

For General Supplementation (Without Deficiency)

• Adults aged 19-70 years should take 600-800 IU daily of vitamin D3. 2
• Adults aged 71+ years should take 800-1,000 IU daily of vitamin D3. 2
• High-risk populations (dark-skinned, veiled, elderly, institutionalized) should receive 800 IU daily without requiring baseline testing. 1, 2

For Documented Deficiency (<20 ng/mL)

• Loading phase: 50,000 IU of vitamin D3 once weekly for 8-12 weeks. 2
• Maintenance phase: 2,000 IU daily or 50,000 IU monthly (equivalent to ~1,600 IU daily). 2, 5
• Target serum 25(OH)D level: at least 30 ng/mL for optimal health benefits, particularly for anti-fracture efficacy. 1, 2

Alternative Forms in Special Circumstances

Calcifediol (25-hydroxyvitamin D3)

Calcifediol may be considered as an alternative to cholecalciferol in patients with malabsorption when intramuscular administration is unavailable or contraindicated. 2, 6

• Calcifediol is 3.2-fold more potent than cholecalciferol, requiring lower dosages. 6
• Calcifediol results in more rapid increases in serum 25(OH)D compared to cholecalciferol. 6
• Calcifediol has higher intestinal absorption rates, providing advantages in malabsorptive conditions. 2, 6
• Calcifediol produces more stable serum levels with intermittent dosing compared to cholecalciferol. 6

Intramuscular Vitamin D3

For patients with documented malabsorption syndromes (post-bariatric surgery, inflammatory bowel disease, short-bowel syndrome), intramuscular vitamin D3 50,000 IU is the preferred route when available. 2

• IM administration results in significantly higher 25(OH)D levels and lower rates of persistent deficiency compared to oral supplementation in malabsorptive populations. 2
• IM vitamin D3 availability varies by country and may be contraindicated in patients on anticoagulation or at high infection risk. 2

Critical Safety Considerations

• Daily doses up to 4,000 IU are generally safe for adults, with some evidence supporting up to 10,000 IU daily for several months. 2, 5
• The upper safety limit for serum 25(OH)D is 100 ng/mL. 1, 2
• Avoid single ultra-high loading doses (>300,000 IU) as they may be inefficient or potentially harmful. 2
• Do not use active vitamin D analogs (calcitriol, alfacalcidol, doxercalciferol, paricalcitol) to treat nutritional vitamin D deficiency. 2

Monitoring Protocol

• Recheck 25(OH)D levels at least 3 months after initiating supplementation to allow plateau to be reached. 1, 2
• If using intermittent dosing (weekly or monthly), measure levels just prior to the next scheduled dose. 2
• Individual response to vitamin D supplementation varies due to genetic differences in vitamin D metabolism, making monitoring essential. 2

Common Pitfalls to Avoid

• Do not assume D2 and D3 are equivalent—this outdated assumption is based on 70-year-old rickets studies and contradicted by modern evidence. 4
• Do not prescribe ergocalciferol (D2) when cholecalciferol (D3) is available, as D2 is less stable, less potent, and has shorter duration of action. 3, 4
• Ensure adequate calcium intake (1,000-1,500 mg daily) alongside vitamin D supplementation for optimal bone health. 2
• Account for seasonal variation in vitamin D levels, with levels typically lowest after winter months. 2