Some basic vitamin D issues 24. August 2008 William Davis (7) The last post on vitamin D raised a number of basic questions among readers. So let me discuss some of these questions one by one. All of them raise important issues surrounding the practical aspects of managing vitamin D in your health. Anne said:I think it is important to stress that vitamin D supplementation needs to be continued long term. I have met too many people who have been prescribed 50,000 IU of D2 for 8-12 weeks and then told to stop because their 23(OH)D went over 30ng/ml. I know one person who's doctor stopped and started the D2 3 times. Thanks for pointing that out, Anne. Excellent point. I also see doctors do this with statin drugs: start it, check a LDL level which is lower, then think that you're done and stop the drug. What the heck are they thinking? If vitamin D is not being produced by sun exposure and not obtainable through diet, continued supplementation is necessary, essentially for life. Twinb asked:How often you think Vit. D levels should be tested after the initial test is done, especially if the levels are drastically low?We have used every 6 months in the office. Ideally, levels are in mid-summer and mid- to-late winter in order to gauge the extremes of your seasonal fluctuations. While most adults over 40 fail to fluctuate more than 10 ng/ml in the Wisconsin climate (and this summer, after an initial rainy season early, has been flawlessly bright and sunny, in the high-70s and 80s every single day for months), an occasional person fluctuates more widely. The only way to judge is to check a blood level. Rich said:Vitamin D dosage effects appear to be quite idiosyncratic.Yes, indeed it is. Despite using crude rules-of-thumb, like taking 1000 units of vitamin D per 10 ng/ml desired (a rule I learned from Dr. John Cannell, which he offered fully aware of its inaccuracy), many people will surprise you and have levels that make no sense. Testing is crucial to know your vitamin D level. Richard asked: Where do we get enough vitamin D wihout worring about laboratory tests? Well, the entire point of the post was that you absolutely, positively cannot just take vitamin D blindly at any dose and hope that your level is ideal, no more than you can blindly take a dose of thyroid and know you have achieved normal thyroid levels. In my view, vitamin D blood levels are an absolute. Another simple issue: Don't be afraid of vitamin D. It is, in all practicality, no more dangerous than getting a dark tan. (But, as many of you realize, getting a tan is no assurance of raising vitamin D if you are over 40 years old.)Wouldn't it be great if someone developed a do-it-yourself-at-home skin test for vitamin D? I know of no effort to develop this, but it would be a huge advantage for all of us.