From the Guidelines
The recommended daily intake of vitamin D for most adults is 600-800 IU (15-20 mcg) per day, with higher doses of 1,000-2,000 IU often suggested for those with deficiency, as supported by the most recent and highest quality study 1.
Key Considerations
- The exact replacement dose depends on the individual's current vitamin D level, age, weight, sun exposure, and medical conditions.
- Vitamin D3 (cholecalciferol) is more effective than vitamin D2 (ergocalciferol) in raising 25(OH)D concentrations and maintaining those levels for a longer time when longer dosing intervals are employed 1.
- For severe deficiency, healthcare providers may prescribe 50,000 IU weekly for 8-12 weeks followed by a maintenance dose, with regular monitoring through blood tests to ensure levels reach the target range of 30-50 ng/mL without exceeding safe limits.
Important Factors
- Vitamin D is essential for calcium absorption and bone health, and also plays roles in immune function and inflammation reduction.
- Taking vitamin D with food containing some fat improves absorption.
- The use of the terms “daily” and “per day” in these recommendations may give the false impression that a day without sunshine requires a dose of supplement, as 25(OH)D3 has a half-life of 2 weeks to 3 months, and is stored primarily in adipose tissue and, to a lesser extent, in the liver 1.
Dosage and Administration
- The Institute of Medicine suggests a daily use of vitamin D of 600 IU for individuals from 1 to 70 years of age, and 800 IU for individuals 71 and older, with a “safe upper limit” of dietary vitamin D intake as 4000 IU daily 1.
- Major institutions have used dosing schedules as infrequent as once every 1–4 months, and it may be more correct to refer to a monthly requirement, which may vary depending on age and season 1.
From the Research
Recommended Dosage for Vitamin D Replacement
The recommended dosage for vitamin D replacement varies depending on the individual's level of deficiency, body mass index (BMI), and other factors.
- For adults with vitamin D deficiency, a loading dose of 300,000 IU administered over 5 or 10 weeks is effective for repletion, as shown in a study published in 2024 2.
- A maintenance dose of 2000 IU daily is adequate to achieve the target vitamin D levels, according to the same study 2.
- Another study published in 2009 recommends oral ergocalciferol (vitamin D2) at 50,000 IU per week for eight weeks to treat vitamin D deficiency, followed by maintenance dosages of cholecalciferol (vitamin D3) at 800 to 1,000 IU per day 3.
- For patients with increased risk of vitamin D deficiency, such as those with obesity or multi-morbidity, daily doses of 7000 IU or intermittent doses of 30,000 IU/week may be considered, as suggested in a narrative review published in 2024 4.
- A European expert panel recommends a vitamin D supplementation dose of 800 to 2000 IU per day for adults, with higher doses (e.g., 6000 IU per day) used for the first 4 to 12 weeks of treatment if a rapid correction of vitamin D deficiency is clinically indicated 5.
- The Osteoporosis Research and Information Group (GRIO) recommends measuring the 25(OH)D concentration prior to supplementation and providing vitamin D supplementation to obtain a concentration between 30 and 60 ng/mL, with a daily supplementation of 800-1000 IU and calcium intake optimization if needed 6.
Special Considerations
- Overweight and obese patients may require higher doses to reach the same vitamin D levels, as shown in a study published in 2024 2.
- Patients with liver disease or malabsorption syndromes may require higher doses or more frequent supplementation, as suggested in a narrative review published in 2024 4.
- The use of intermittent long-term high doses vitamin D supplementation may increase the risk of falls, fracture, and premature death in certain populations, as discussed in a position statement published in 2025 6.