Vitamin D is much prescribed as seen on most of the prescription papers by majority of physicians and there is no trend to repeat the test how it is assessed and when and how to treat if toxicity occurs and how a physician can know it without lab tests ?
Vitamin D toxicity is a rare but potentially serious condition that occurs when you have excessive amounts of vitamin D in your body. Vit D toxicity is usually caused by megadoses of vitamin D supplements — not by diet or sun exposure. That's because your body regulates the amount of vit D produced by sun exposure, and even fortified foods don't contain large amounts of vit D. The main consequence of vitamin D toxicity is a buildup of calcium in your blood (hypercalcemia), which can cause nausea and vomiting, weakness, and frequent urination. Symptoms might progress to bone pain and kidney problems, such as the formation of calcium stones. Treatment includes stopping vitD intake and restricting dietary calcium.
Please check
1. Maria G. Vogiatzi, Elka Jacobson-Dickman, Mark D. DeBoer. Vitamin D Supplementation and Risk of Toxicity in Pediatrics: A Review of Current Literature. J Clin Endocrinol Metab, April 2014, 99(4):1132–1141. doi: 10.1210/jc.2013-3655.
2. Parvaiz A. Koul, Sheikh Hilal Ahmad, Feroze Ahmad, Rafi A. Jan, S.U. Shah, Umar H. Khan .Vitamin D Toxicity in Adults: A Case Series from an Area with Endemic Hypovitaminosis D. Oman Medical Journal (2011) Vol. 26, No. 3: 201-204 DOI 10. 5001/omj.2011.49
3. Fahad Alshahrani and Naji Aljohani .Vitamin D: Deficiency, Sufficiency and Toxicity. Nutrients 2013, 5, 3605-3616; doi:10.3390/nu5093605
The amount of vitamin D prescribed for maintaining a sufficient status (75 nmol/L 25OH vit D3) is about 1000 - 2000 iU/day, depending on diet and sun exposure.
In deep deficiency stoss therapy is applied (giving doses up to 300.000 iU in one single dose or divided over a some weeks). It has been shown that such dose is not toxic, it is more or less one full-year dose.
See for example the Cipriani paper in JCEM 2010 "Effect of a Single Oral Dose of 600,000 IU of
Cholecalciferol on Serum Calciotropic Hormones in Young Subjects with Vitamin D Deficiency: A Prospective Intervention Study"
However, in some regimes doctors are given much more. As a rule of thump one should not give more than 25000 iU/d, see Hathcock and Vieth AmJClinNutr 2007 "Risk assessment for vitamin D"
Personally I recommend not to give more than 50.000 iU in a single dose and spread over one or two month a maximum of 300.000 iU. Doing this the chance of hypercalcemia (the toxic effect of vit D overdose) is neglegible. But I agree that doctors giving stoss therapy should watch their patients.
Nice and really documented answers very informative thanks every body
There is a wide range between lower limit and toxicity, so they feel safe when prescribe it.
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