Vitamin D daily dose: how much do you really need?

The short answer: 600–800 IU/day for most adults; 1,000–2,000 IU/day if deficient

Vitamin D requirements depend on age, latitude, skin color, season, and baseline serum levels. The Endocrine Society and Institute of Medicine both recommend 600–800 IU per day as the general adult target, with higher doses for people with documented deficiency, limited sun exposure, or darker skin.

Daily recommended intake by age

| Age | RDA (IU/day) | Upper tolerable limit (IU/day) | |---|---|---| | 0–12 months | 400 | 1,000–1,500 | | 1–13 years | 600 | 2,500–3,000 | | 14–70 years | 600 | 4,000 | | 71+ years | 800 | 4,000 | | Pregnant/breastfeeding | 600 | 4,000 |

Who needs more than 600 IU?

• Serum 25(OH)D <20 ng/mL (50 nmol/L) — officially deficient. Repletion typically 2,000–5,000 IU/day for 8–12 weeks, then maintenance 1,000–2,000 IU/day.
• Darker skin tones — melanin reduces skin synthesis by up to 10×; people with darker skin often need 1,000–2,000 IU/day supplementation.
• Limited sun exposure (office workers, high latitudes, veiling clothing) — winter months especially.
• Obesity (BMI ≥30) — vitamin D is sequestered in adipose tissue; requirements are 2–3× higher.
• Older adults — skin synthesis drops 50–75% after age 70.
• Malabsorption disorders (celiac, Crohn's, post-bariatric surgery) — higher doses or prescription.
• Chronic kidney disease — active form (calcitriol) often prescribed.

When to test your level

Serum 25(OH)D testing is reasonable for:

• Symptoms of deficiency (fatigue, bone pain, muscle weakness, frequent infections)
• Risk factors listed above
• Osteoporosis or low-trauma fractures