What is the recommended daily dose of vitamin D (International Units)?

Recommended Vitamin D Dosage

For healthy adults, take 600-800 IU daily as a baseline, but if you have risk factors for deficiency (obesity, dark skin, limited sun exposure, malabsorption, chronic illness), you should take 1500-2000 IU daily. 1

Standard Dosing by Age and Health Status

Healthy Adults

• Ages 18-70 years: 600 IU daily meets the needs of 97.5% of the population 1, 2
• Ages 71+ years: 800 IU daily to account for decreased skin synthesis with aging 1, 2
• These doses maintain adequate vitamin D status in most individuals without specific risk factors 1

At-Risk Populations Requiring Higher Doses

You need 1500-2000 IU daily if you have any of these risk factors: 1

• Obesity (vitamin D is sequestered in adipose tissue) 1, 3
• Dark skin or veiled/covered clothing with limited sun exposure 1
• Institutionalized or homebound status 1
• Malabsorption syndromes (inflammatory bowel disease, celiac disease, pancreatic insufficiency) 4, 1
• Post-bariatric surgery patients 4, 1
• Chronic kidney disease 5
• Chronic glucocorticoid use (≥2.5 mg/day for >3 months) 1

Target Blood Levels

The optimal target range for serum 25(OH)D is 30-50 ng/mL for most health benefits, including bone health and fracture prevention 1, 6, 7. The upper safety limit is 100 ng/mL, which should never be exceeded 1, 6.

Important Context on Blood Levels

• Levels below 20 ng/mL indicate deficiency requiring treatment 5, 2
• Levels between 20-30 ng/mL represent insufficiency 5
• Anti-fracture efficacy begins at achieved levels of at least 30 ng/mL 5
• There is no evidence that levels above 50 ng/mL provide additional benefits 6

Practical Dosing Guidelines

Rule of Thumb for Dose Adjustment

Each 1,000 IU of daily vitamin D increases serum 25(OH)D by approximately 10 ng/mL, though individual responses vary due to genetic differences in vitamin D metabolism 1, 6.

Dosing Frequency Options

• Daily dosing is physiologically preferred and most effective 4, 1
• Weekly dosing (e.g., 7,000 IU once weekly) is acceptable for convenience 1, 3
• Monthly dosing (e.g., 50,000 IU monthly, equivalent to ~1,600 IU daily) can be used but is less ideal 5
• Avoid single annual mega-doses (≥500,000 IU), as these have been associated with increased falls and fractures 1

Special Situations Requiring Higher Doses

Patients with Recurrent Deficiency

If you have repeatedly low vitamin D levels despite standard supplementation, take 4000-5000 IU daily for 2 months to achieve blood levels of 40-60 ng/mL 4. This applies to patients with:

• Inflammatory bowel disease 4
• Chronic liver disease 4
• Pancreatic insufficiency 4
• Chronic intestinal failure 4
• Post-bariatric surgery 4, 5

Obese Patients

Obese patients may require 6,000-10,000 IU daily as treatment, followed by maintenance doses of 3,000-6,000 IU daily, due to sequestration of vitamin D in adipose tissue 1, 3.

Safety Considerations

Safe Upper Limits

• Daily doses up to 4,000 IU are generally considered safe for long-term use in adults 4, 1, 6
• The Endocrine Society has recommended an upper limit of 10,000 IU daily for at-risk patients 4
• Most international authorities consider 2,000 IU daily as absolutely safe 1, 6

Toxicity Risk

Vitamin D toxicity is rare but can occur with: 4

• True overdoses (typically single doses of millions of IU or daily doses >10,000-100,000 IU)
• Manufacturing errors
• Increased vitamin D sensitivity (genetic mutations)

Toxicity symptoms include hypercalcemia, hypercalciuria, dizziness, and renal failure 4. Hypercalcemia generally occurs only when daily intake exceeds 100,000 IU or when 25(OH)D levels exceed 100 ng/mL 1, 6.

When to Check Blood Levels

Who Should Be Tested

You should measure your 25(OH)D level before starting supplementation if you have: 6

• Musculoskeletal health problems
• Cardiovascular disease
• Autoimmune disease
• Cancer or cancer risk factors
• Symptoms suggesting deficiency (bone pain, muscle weakness, frequent falls)

Who Can Start Without Testing

You can start 800 IU daily without baseline testing if you are: 1, 6

• Dark-skinned or veiled with limited sun exposure
• Age 65 or older
• Institutionalized or homebound

Monitoring After Starting Supplementation

Wait at least 3 months after starting supplementation before measuring 25(OH)D levels to allow a plateau to be reached 1, 5, 6. If using intermittent dosing (weekly or monthly), measure just prior to the next scheduled dose 5.

Common Pitfalls to Avoid

Dosing Errors

• Don't use vitamin D2 (ergocalciferol) for intermittent dosing—vitamin D3 (cholecalciferol) maintains serum levels longer and is more bioavailable 5
• Don't assume standard doses work for everyone—obese patients, those with malabsorption, and those on certain medications (anticonvulsants, glucocorticoids) need higher doses 1, 3
• Don't use single large bolus doses (monthly 50,000 IU) for routine supplementation—daily or weekly dosing is more effective 1

Monitoring Errors

• Don't check levels too soon—wait at least 3 months for stabilization 1, 6
• Don't ignore seasonal variation—levels are typically lowest after winter 4, 6
• Don't forget to ensure adequate calcium intake (1,000-1,500 mg daily from diet plus supplements) alongside vitamin D supplementation 5

Nutritional Support Considerations

Enteral Nutrition

Patients receiving enteral nutrition should get at least 1,000 IU (25 mcg) per day in 1,500 kcal of feeding 4. Standard enteral formulas often provide only 400-800 IU/day, which may be inadequate 4.

Parenteral Nutrition

Patients on parenteral nutrition should receive at least 200 IU (5 mcg) of vitamin D per day, though some will have higher requirements that should be checked by blood determination 4.