From the Guidelines
High dose vitamin D therapy should be initiated when serum 25-hydroxyvitamin D (25-OH vitamin D) levels fall below 20 ng/mL (50 nmol/L), which indicates vitamin D deficiency. This recommendation is based on the most recent and highest quality study available, which suggests that a level below 50-75 nmol/L (or 20-30 ng/ml) of serum/plasma 25(OH)D concentration is considered to define vitamin D deficiency 1. For patients with levels between 20-30 ng/mL (50-75 nmol/L), considered vitamin D insufficiency, treatment may also be appropriate depending on clinical circumstances.
The recommended high-dose regimen for deficiency is vitamin D2 (ergocalciferol) or D3 (cholecalciferol) at 50,000 IU weekly for 8-12 weeks, followed by maintenance therapy of 1,000-2,000 IU daily. For severe deficiency (levels <10 ng/mL), some clinicians may use higher loading doses. After the initial treatment period, repeat testing of 25-OH vitamin D levels is recommended to ensure the deficiency has been corrected. Patients with certain conditions like malabsorption, obesity, or those taking medications that affect vitamin D metabolism may require higher or more prolonged dosing.
Key considerations for initiating high dose vitamin D therapy include:
- Serum 25-OH vitamin D levels below 20 ng/mL (50 nmol/L) indicating vitamin D deficiency
- Clinical circumstances such as malabsorption, obesity, or medications affecting vitamin D metabolism
- Recommended high-dose regimen of vitamin D2 or D3 at 50,000 IU weekly for 8-12 weeks, followed by maintenance therapy
- Repeat testing of 25-OH vitamin D levels after initial treatment period to ensure deficiency correction. Vitamin D is essential for calcium absorption and bone health, and deficiency can lead to osteomalacia in adults and rickets in children, as well as potentially contributing to other health issues including muscle weakness and increased fall risk 1.
From the Research
Initiating High-Dose Vitamin D Therapy
To determine when to start high-dose vitamin D therapy, it's essential to consider the serum 25-hydroxyvitamin D (25-OH vitamin D) level.
- The definition of vitamin D deficiency is a serum 25-hydroxyvitamin D level of less than 20 ng per mL (50 nmol per L), and insufficiency is defined as a serum 25-hydroxyvitamin D level of 20 to 30 ng per mL (50 to 75 nmol per L) 2.
- Severe vitamin D deficiency with a 25(OH)D concentration below <30 nmol/L (or 12 ng/ml) dramatically increases the risk of excess mortality, infections, and many other diseases, and should be avoided whenever possible 3.
Treatment Goals and Dosage
The goal of treatment is to normalize vitamin D levels to relieve symptoms and decrease the risk of fractures, falls, and other adverse health outcomes.
- In persons with vitamin D deficiency, treatment may include oral ergocalciferol (vitamin D2) at 50,000 IU per week for eight weeks 2.
- After vitamin D levels normalize, experts recommend maintenance dosages of cholecalciferol (vitamin D3) at 800 to 1,000 IU per day from dietary and supplemental sources 2.
- A daily vitamin D supplementation with 2000 IU (50 µg) may be considered a simple, effective, and safe dosage to prevent and treat vitamin D deficiency in the adult general population 4.
Serum 25-Hydroxyvitamin D Levels and Supplementation
Vitamin D modulates fracture risk in two ways: by decreasing falls and increasing bone density.
- Fall prevention was only observed in a trial of at least 700 IU vitamin D per day, and fracture prevention required a received dose (treatment dose*adherence) of more than 400 IU vitamin D per day 5.
- Anti-fall efficacy started with achieved 25-hydroxyvitamin D levels of at least 60 nmol l(-1) (24 ng ml(-1)) and anti-fracture efficacy started with achieved 25-hydroxyvitamin D levels of at least 75 nmol l(-1) (30 ng ml(-1)) and both endpoints improved further with higher achieved 25-hydroxyvitamin D levels 5.
- Vitamin D alone appears as effective as combined calcium/vitamin D treatment in restoring serum vitamin D levels in older community dwelling and institutionalised patients 6.