What is the recommended dose of vitamin D (International Units) for adults with a deficiency?

Recommended Vitamin D Dosing for Adults with Deficiency

For adults with documented vitamin D deficiency (<20 ng/mL), the standard treatment is 50,000 IU of cholecalciferol (vitamin D3) weekly for 8-12 weeks, followed by maintenance therapy of 800-2,000 IU daily. 1, 2

Treatment Protocol Based on Deficiency Severity

Severe Deficiency (<10-12 ng/mL)

• Administer 50,000 IU cholecalciferol weekly for 12 weeks, then transition to monthly maintenance dosing of 50,000 IU (equivalent to approximately 1,600 IU daily) 1, 2
• This approach is particularly important for patients with symptoms, high fracture risk, or secondary causes of osteoporosis 3

Standard Deficiency (10-20 ng/mL)

• Prescribe 50,000 IU cholecalciferol weekly for 8-12 weeks 1, 2, 4
• Alternative rapid correction: 6,000 IU daily for 4-12 weeks if clinically indicated 5
• After repletion, continue with 800-2,000 IU daily for maintenance 1, 2

Insufficiency (20-30 ng/mL)

• Treat with 4,000 IU cholecalciferol daily for 12 weeks, OR 50,000 IU every other week for 12 weeks 2
• Alternatively, add 1,000 IU daily to current intake and recheck in 3 months 1

Maintenance Therapy After Achieving Target Levels

• Target serum 25(OH)D level: ≥30 ng/mL for optimal bone health, anti-fracture efficacy, and cardiovascular benefits 3, 1, 2
• Maintenance options: 800-2,000 IU daily OR 50,000 IU monthly 1, 2
• For elderly patients (≥65 years): minimum 800 IU daily even without baseline measurement 3, 2
• The Endocrine Society recommends at least 2,000 IU daily for optimal health benefits 1

Formulation Preference

• Cholecalciferol (vitamin D3) is strongly preferred over ergocalciferol (vitamin D2) because it maintains serum levels longer and has higher bioavailability 1, 2
• The rule of thumb: 1,000 IU daily increases 25(OH)D by approximately 10 ng/mL, though individual responses vary 3, 5

Special Populations Requiring Higher Doses

Malabsorption Syndromes

• Intramuscular vitamin D3 50,000 IU is the preferred route for patients with documented malabsorption (post-bariatric surgery, inflammatory bowel disease, short-bowel syndrome) who fail oral supplementation 1
• When IM unavailable: 4,000-5,000 IU daily orally for 2 months, or at least 2,000 IU daily for post-bariatric patients 1

Obesity

• Obese patients require higher doses due to sequestration in adipose tissue 6
• Consider 7,000 IU daily or 30,000 IU weekly for prolonged prophylaxis 6
• For treatment without monitoring: 30,000 IU twice weekly or 50,000 IU weekly for 6-8 weeks only 6

Chronic Kidney Disease (CKD)

• For CKD with GFR 20-60 mL/min/1.73m², treat nutritional vitamin D deficiency with ergocalciferol or cholecalciferol using standard protocols 1, 2
• Do NOT use active vitamin D analogs (calcitriol, alfacalcidol, doxercalciferol, paricalcitol) to treat nutritional vitamin D deficiency 1, 2

Dark-Skinned, Veiled, or Institutionalized Individuals

• Supplement with 800 IU daily without requiring baseline measurement 3, 2

Monitoring Protocol

• Recheck 25(OH)D levels after 3-6 months of treatment to ensure adequate response and guide ongoing therapy 1, 2, 5
• If using intermittent regimens (weekly/monthly), measure just prior to the next scheduled dose 1
• Individual response is highly variable due to genetic differences in vitamin D metabolism, body composition, and environmental factors 1, 2

Calcium Co-Administration

• Ensure adequate calcium intake of 1,000-1,500 mg daily (from diet plus supplements if needed) alongside vitamin D supplementation 1, 2
• Calcium supplements should be taken in divided doses of no more than 600 mg 1

Safety Considerations and Upper Limits

• Daily doses up to 4,000 IU are generally considered safe for adults 3, 1, 2
• Some evidence supports up to 10,000 IU daily for several months without adverse effects 3, 1
• Upper safety limit for serum 25(OH)D: 100 ng/mL 3, 1
• Vitamin D toxicity manifests as hypercalcemia, hyperphosphatemia, suppressed PTH, and hypercalciuria 1

Critical Pitfalls to Avoid

• Never use single ultra-high loading doses (>300,000 IU) as they may be inefficient or potentially harmful, particularly for fall and fracture prevention 1, 2
• Do not use active vitamin D analogs for nutritional deficiency 1, 2
• Do not neglect calcium supplementation alongside vitamin D 1, 2
• Do not assume standard daily allowances (600-800 IU) are adequate for correcting deficiency—they are insufficient 7
• Account for seasonal variation when interpreting levels (lowest after winter) 3

Practical Dosing Equivalents

• 50,000 IU monthly ≈ 1,600 IU daily 1
• 30,000 IU weekly ≈ 4,300 IU daily 6
• For enteral nutrition: provide at least 1,000 IU per day in 1,500 kcal 3, 2
• For parenteral nutrition: provide at least 200 IU per day 3, 2