What are the implications of replacing Vitamin D3 at a level of 13, indicating a deficiency in Vitamin D3 (Cholecalciferol)?

From the Guidelines

To replace vitamin D3 at a level of 13 ng/mL, I recommend taking a prescription vitamin D (ergocalciferol) 50,000 IU weekly for 8 weeks, followed by a recheck of the serum 25(OH) D level, with subsequent dosing based on the results, as suggested by the NCCN task force report 1. When considering vitamin D supplementation, it's essential to note that vitamin D3 (cholecalciferol) is more effective in raising 25(OH) D concentrations and maintaining those levels for a longer time when longer dosing intervals are employed 1. Some key points to consider when supplementing vitamin D include:

• The goal of supplementation is to bring serum 25(OH) D levels to 30 ng/ml (75 nmol/L) or higher for bone health 1
• Vitamin D toxicity is uncommon but may occur with daily doses of more than 50,000 IU per day that produce 25(OH) D levels larger than 150 ng/mL 1
• Current expert opinion on supplementation for adults older than age 50 is 1200 mg of calcium (from all sources) and 800 to 1000 IU of vitamin D daily, which may also be recommended for younger patients at risk for cancer treatment–associated bone loss 1 It's crucial to monitor serum 25(OH) D levels after supplementation to ensure they've increased to the optimal range, and adjust the dosage accordingly.

From the FDA Drug Label

Therapeutic dosage should be readjusted as soon as there is clinical improvement. IN VITAMIN D RESISTANT RICKETS THE RANGE BETWEEN THERAPEUTIC AND TOXIC DOSES IS NARROW.

Replacing vitamin D3 at a level of 13 is not directly addressed in the provided drug labels.

• No specific dosage level of 13 is mentioned for replacing vitamin D3.
• The labels emphasize the importance of individualized dosage and careful monitoring to prevent toxic effects.
• Clinical improvement should guide the readjustment of therapeutic dosage. 2

From the Research

Replacing Vitamin D3 at a Level of 13

• The optimal level of vitamin D replacement is still a topic of debate, with some studies suggesting that vitamin D3 may be more effective than vitamin D2 in raising serum 25-hydroxyvitamin D levels 3.
• A study published in 2016 found that vitamin D3 increased total and free 25-hydroxyvitamin D levels to a greater extent than vitamin D2, and that free 25-hydroxyvitamin D may be a superior marker of vitamin D bioactivity 3.
• Another study published in 2014 found that a daily dose of 2000 IU of vitamin D3 raised 25-hydroxyvitamin D levels to ≥ 20 ng/mL in 96% of adolescents, and to ≥ 30 ng/mL in 64% of adolescents 4.
• However, a study published in 2009 found that vitamin D2 and vitamin D3 had equivalent effects on intestinal calcium absorption in Nigerian children with rickets, and that fractional calcium absorption did not increase with either vitamin D2 or vitamin D3 supplementation 5.
• A systematic review published in 2014 found that vitamin D3 decreased mortality in all 56 trials analyzed together, but that vitamin D2, alfacalcidol, and calcitriol did not have a significant effect on mortality 6.
• The same review found that vitamin D3 combined with calcium increased the risk of nephrolithiasis, and that alfacalcidol and calcitriol increased the risk of hypercalcaemia 6.

Key Findings

• Vitamin D3 may be more effective than vitamin D2 in raising serum 25-hydroxyvitamin D levels 3.
• A daily dose of 2000 IU of vitamin D3 may be sufficient to raise 25-hydroxyvitamin D levels to ≥ 20 ng/mL in adolescents 4.
• Vitamin D2 and vitamin D3 may have equivalent effects on intestinal calcium absorption in certain populations 5.
• Vitamin D3 may decrease mortality, but may also increase the risk of nephrolithiasis when combined with calcium 6.