Is taking 5000 International Units (IU) of cholecalciferol (Vitamin D3) daily for 8 weeks excessive and does it necessitate monitoring of vitamin D levels to prevent hypercalcemia?

From the Guidelines

Taking vitamin D3 5000 IU daily for 8 weeks is generally considered safe for treating vitamin D deficiency, but you should get your levels checked soon. For most adults with deficiency, 5000 IU daily is an appropriate treatment dose for 8-12 weeks, followed by a maintenance dose of 1000-2000 IU daily once levels normalize 1. I recommend scheduling a blood test to check your 25-hydroxyvitamin D levels to ensure they're reaching the target range (typically 30-50 ng/mL) without becoming excessive (above 100 ng/mL). Vitamin D is fat-soluble and can accumulate in your body, potentially causing hypercalcemia at very high levels over extended periods. Your doctor may adjust your dosage based on your test results, your specific health conditions, and severity of your initial deficiency. While taking vitamin D, ensure adequate calcium intake and consider taking it with meals containing some fat to improve absorption. Some key points to consider:

• The recommended daily intake of vitamin D varies by age, with 600 IU recommended for adults aged 18-70 and 800 IU for those over 70 1.
• Vitamin D3 is preferred over vitamin D2 for supplementation, as it maintains serum 25(OH)D2 concentration for a longer period 1.
• It's essential to monitor your vitamin D levels and adjust your dosage accordingly to avoid excessive levels, which can lead to hypercalcemia.
• A maintenance dose of 1000-2000 IU daily is typically recommended once levels normalize, but this may vary depending on individual factors, such as diet and health conditions 1.

From the Research

Vitamin D3 Supplementation

• The study 2 found that long-term supplementation with vitamin D3 in doses ranging from 5000 to 50,000 IUs/day appears to be safe, with no cases of vitamin D3-induced hypercalcemia or adverse events attributable to vitamin D3 supplementation.
• However, another study 3 found that long-term vitamin D supplementation resulted in increased risks of hypercalcemia and hypercalciuria, which were not dose-related.

Checking Vitamin D Levels

• It is essential to monitor vitamin D levels, especially when taking high doses of vitamin D3, as excessive levels can lead to hypercalcemia and other adverse effects 3, 4.
• The study 2 found that patients on D3 supplementation had a mean 25OHD3 level of 118.9 ng/ml, with a range from 74.4 to 384.8 ng/ml, highlighting the importance of regular monitoring.

Risks of High-Dose Vitamin D3 Supplementation

• High-dose vitamin D3 supplementation may increase the risk of kidney stone formation, particularly in individuals predisposed to hypercalciuria 4, 5.
• The study 3 found that vitamin D supplementation did not increase the risk of kidney stones, but subgroup analyses suggested that the effect of vitamin D supplementation on risk of hypercalcemia, hypercalciuria, or kidney stones was not modified by baseline 25-hydroxyvitamin D, vitamin D dose and duration, or calcium co-supplementation.

Recommendations

• Based on the study 2, taking 5000 IU of vitamin D3 per day for 8 weeks may not be excessive, but it is crucial to monitor vitamin D levels and adjust the dosage as needed to avoid adverse effects.
• Regular monitoring of vitamin D levels, calcium levels, and kidney function is recommended when taking high-dose vitamin D3 supplementation 3, 4.