Vitamin D Dosage Chart
Vitamin D (cholecalciferol / D3) is a fat-soluble vitamin essential for calcium absorption, bone density, and immune function. Optimal levels depend on body weight, baseline serum 25(OH)D, geographic location, and skin pigmentation. Doses range from 600 IU for maintenance to 5,000+ IU for repletion.
Vitamin D Dosage by Age Group
| Age Group | Age Range | Dose Range | Notes |
|---|---|---|---|
| Infants (0–12 mo) | 0–12 months | 400 IU | Daily drops; breastfed infants especially need supplementation |
| Children (1–18 yr) | 1–18 years | 600–1000 IU | RDA is 600 IU; 1,000 IU if limited sun exposure |
| Adults — maintenance | 18–64 years | 1500–2000 IU | Based on Endocrine Society guidelines |
| Adults — repletion (deficient) | 18–64 years | 2000–5000 IU | Continue 8–12 weeks; retest serum 25(OH)D |
| Seniors (65+) | 65+ years | 2000–4000 IU | Decreased skin synthesis + lower dietary intake |
Weight-Based Dosage Calculator
Enter your weight to calculate a personalized Vitamin D dose based on body weight. Some endocrinologists use 40–60 IU/kg/day for personalized dosing. A 70 kg adult = 2,800–4,200 IU/day.
When and how to take Vitamin D
Take with a fatty meal (lunch or dinner) to maximize absorption — vitamin D is fat-soluble. Morning or evening does not significantly affect efficacy.
Available Forms
Most effective form for raising serum 25(OH)D. Preferred over D2.
Available as softgels, drops, tablets
Plant-based (vegan-friendly) but less potent at raising blood levels.
Requires ~2× the D3 dose for equivalent effect
Co-supplementation with K2 (MK-7) may improve calcium distribution.
Useful for those supplementing at 2,000+ IU/day
Safety Cautions
- Upper tolerable intake level: 4,000 IU/day for adults (RDA guideline). Many experts consider 10,000 IU/day the practical safety limit.
- Toxicity (hypercalcemia) is rare below 10,000 IU/day but possible — test serum 25(OH)D before dosing above 5,000 IU.
- Fat malabsorption conditions (Crohn's, celiac) significantly reduce vitamin D absorption.
- Certain medications (steroids, anticonvulsants, weight-loss drugs) reduce vitamin D efficacy.
- Infants should not exceed 1,000 IU/day without physician oversight.
Frequently Asked Questions
How much vitamin D should I take per day?
For most adults, 1,500–2,000 IU/day is the maintenance dose recommended by the Endocrine Society. If you have confirmed deficiency (serum 25(OH)D below 20 ng/mL), repletion doses of 2,000–5,000 IU/day are typical for 8–12 weeks, followed by retesting.
What is 1,000 IU of vitamin D in mcg?
1,000 IU of vitamin D3 equals 25 mcg. The conversion is: IU ÷ 40 = mcg. So 2,000 IU = 50 mcg, and 4,000 IU = 100 mcg. EU supplement labels use mcg while US labels often show IU.
Can I take vitamin D without vitamin K?
Yes, but if you supplement above 2,000 IU/day, adding vitamin K2 (MK-7, 90–200 mcg) is often recommended to support proper calcium metabolism and prevent soft-tissue calcification. This is precautionary, not mandatory.
Sources & References
- Endocrine Society Clinical Practice Guideline: Vitamin D Deficiency
- NIH ODS — Vitamin D Fact Sheet
- Holick MF, NEJM 2007 — Vitamin D Deficiency