Blood vitamin D levels

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In response to the comment on what is a safe blood vD level:

Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr. 1999 May;69(5):842-56. 

For adults, the 5-microg (200 IU) vitamin D recommended dietary allowance may prevent osteomalacia in the absence of sunlight, but more is needed to help prevent osteoporosis and secondary hyperparathyroidism. Other benefits of vitamin D supplementation are implicated epidemiologically: prevention of some cancers, osteoarthritis progression, multiple sclerosis, and hypertension. Total-body sun exposure easily provides the equivalent of 250 microg (10000 IU) vitamin D/d, suggesting that this is a physiologic limit. Sailors in US submarines are deprived of environmentally acquired vitamin D equivalent to 20-50 microg (800-2000 IU)/d. The assembled data from many vitamin D supplementation studies reveal a curve for vitamin D dose versus serum 25-hydroxyvitamin D [25(OH)D] response that is surprisingly flat up to 250 microg (10000 IU) vitamin D/d. To ensure that serum 25(OH)D concentrations exceed 100 nmol/L, a total vitamin D supply of 100 microg (4000 IU)/d is required. Except in those with conditions causing hypersensitivity, there is no evidence of adverse effects with serum 25(OH)D concentrations <140 nmol/L, which require a total vitamin D supply of 250 microg (10000 IU)/d to attain. Published cases of vitamin D toxicity with hypercalcemia, for which the 25(OH)D concentration and vitamin D dose are known, all involve intake of > or = 1000 microg (40000 IU)/d. Because vitamin D is potentially toxic, intake of >25 microg (1000 IU)/d has been avoided even though the weight of evidence shows that the currently accepted, no observed adverse effect limit of 50 microg (2000 IU)/d is too low by at least 5-fold.



You will notice from this table, copied from the paper above, that studies in people with occupations with large quantities of outdoor sun exposure (framers and lifeguards) that their levels are well above 100nmol/L. 

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Prof G

Professor of Neurology, Barts & The London. MS & Preventive Neurology thinker, blogger, runner, vegetable gardener, husband, father, cook and wine & food lover.

3 comments

  • So you are saying that its impossible to rise above 140 nmol/L if you take less that 10000uI/day? Currently my levels are 121 with only 4560uI/day. – with that amount what should my max level then be? (even better – how do you calculate such a thing?(approximated))

    But yes, if what you are saying is that its ok to be under 140nmol/L and being above _may_ cause some issues, then it answers my question.

  • Wow … I take 10,000 IU daily on days when I don't get out in the sun. On days when I go for a walk or am outside for a bit, I take 5,000 IU. My most recent level was 97.9 ng/mL. If I have the correct conversion, then that would be 244 nmol/L!!

    I seemed to have overshot my goal. However, as per the lab reference ranges (for the hospital reporting my results), I am at the upper limit of normal. The ranges are as follows:

    Deficiency = <10 ng/mL (25 nmol/L)
    Insufficiency = 10 – 25 ng/mL (25 – 75 nmol/L)
    Sufficiency = 30 – 100 ng/mL (75 – 250 nmol/L)
    Toxicity = >100 ng/mL (> 250 nmol/L)

  • Re: "So you are saying that its impossible to rise above 140 nmol/L if you take less that 10,000uI/day?"

    Very unlikely. vD levels are controlled by many factors, including genetic factors. If in doubt have your levels checked.

    "Currently my levels are 121 with only 4560uI/day. – with that amount what should my max level then be? (even better – how do you calculate such a thing?(approximated))"

    You can't calculate a max level. In addition, your levels will vary depending on sun exposure; being higher in summer than winter. It looks as if you don't need more than 4,000 per day.

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