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Information on the latest vitamin D news and research.

Find out more information on deficiency, supplementation, sun exposure, and how vitamin D relates to your health.

Hi there, I have some questions about the accuracy of a recent 25(OH)D that I am hoping someone can help me out with. I just received my lab results for a 25(OH)D test, and it indicates that my serum concentration is 39 ng/ml. I am highly convinced that it should be lower than this, as I have been experiencing certain symptoms for years that I strongly believe are related to a vitamin D deficiency. Granted, I realize 39 ng/ml is still considered somewhat low by Vitamin D Council standards, but it is nonetheless higher than I was expecting it to be. Because I took high dose (~10,000 IU) vitamin D supplements daily for two days prior to the test, I am wondering if this can affect the test outcome. To be clear, I took ~10,000 IU for two days, then took one day off from any vitamin D supplementation, then the next day I was tested. That was yesterday and I just received my test results today (which, as a side note, seems awfully fast…). Does anyone know how quickly a high dose of vitamin D can affect serum concentration, especially as it relates to the 25(OH)D lab test? From everything I've read about this subject, it sounds like it can take *months* for serum levels to increase in response to supplementation, and so I am leaning towards believing that these supplements likely did not affect my lab results in any significant way. But I just want to be sure nonetheless. Thanks so much for taking the time to read this, and thanks in advance for any feedback on my question!

General Discussion

Asked by  Anonymous on July 8, 2016


  • Anonymous
     Anonymous on

    See title

    Answered by  Anonymous on

  • IAW
     IAW on

    No I think it “did” affect your results. Someone else asked a question that’s related to yours several days ago.
    What I could find then was that 25OHD appears in 24 hours or less. What most people also do not know/understand is the following. For example if you did not take anymore supplemental D (or sunshine) once you took the test then that 39ng/ml in two weeks would most likely read around 20ng/ml. (This may only hold true if you are not deficient in the first place. People do not “store” Vitamin D for later use until they reach a level of 40ng/ml.)
    If you have been reading this website you know we recommend 5000iu a day for most adults weighing 150lbs. (If you weigh more, you have to take more).
    So if you take the 5000iu a day and your “symptoms” go away, great! If they do not then take more Vitamin D and see if they go away. What if “Mike’s” genetic makeup says he needs a level of 80ng/ml and not 50ng/ml? My point is try not to get “hung up” too much in the numbers/levels.

    Answered by  IAW on

    • Anonymous
       Anonymous on

      Thank you so much for the response! I did not see that someone else recently posted a similar question, and so I do apologize for the repetition. I am new to using this website and so am not yet too familiar with navigating my way around here.

      As for my serum concentration, it sounds like it was likely quite lower prior to my two days of taking ~10,000 IUs? This actually makes sense considering my symptoms have been improving quite a bit since I started taking this high dose vitamin D. This is a pretty big deal considering I have been dealing with these symptoms for YEARS. I therefore was shocked when I saw my lab results because I was expecting it to be much lower.

      Anyway, thanks again. I really appreciate it. I’ll definitely keep all of this in mind!

      Answered by  Anonymous on