How do I know if I have vitamin D deficiency?

Vitamin D deficiency can only be confirmed by a blood test. Fortunately, these tests are readily available and inexpensive. Unfortunately, it is not easy to know what symptoms to look for if you think you might have a low serum level. This article will give you an easy way to determine whether you need a blood test.

First, who might have be low in vitamin D?
Estimates in the literature indicate that over 20% of the North American adult population may have vitamin D deficiency by the end of winter (1). Most people do not get enough vitamin D from their diets. Vitamin D deficiency is defined in the literature as having a low concentration of 25-hydroxyvitamin D3 in your serum (2). Since it's hard to tell that about someone just by looking at them, let's break down the risk factors here.

Factors that increase the likelihood of vitamin D deficiency (3,4):

sunscreen use-- if you regularly use over SPF 15

skin pigment-- dark skinned people make much less vitamin D

aging-- because your skin has less cholesterol

latitude-- if you live above 35 degrees latitude (Las Vegas, most of Europe, Canberra AU)

obesity-- because your body absorbs more of vitamin D

weather/sun exposure-- if you work indoors or live in a city with heavy cloud cover

How do you know if you have a problem?
The unfortunate answer is that you probably won't know it until you get it checked out. And given what we know about the relationship of low vitamin D to cancer and other diseases like diabetes, you probably want to do that . Here are some issues that come up more frequently for people with vitamin D deficiency than for others:

depression and seasonal affective disorder (5)

muscle pain, chronic pain (6)

respiratory infections, wheezing (7)

acne, psoriasis (8)

stress fractures (9)

These symptoms are mostly things we think of as normal problems, and might easily overlook something like vitamin status. If, however, you have some of these symptoms and fit into one of the risk factors listed above, you might want to get yourself checked out in a blood test for vitamin D deficiency here.

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2. Holick, MF. "Vitamin D deficiency." N Engl J Med. 357 (2007) 266-81.
3. Webb, AR. "Who, what, where, and when-influences on cutaneous vitamin D synthesis." Prog Biophys Mol Biol. 92 (2006) 17-25.
4. Chen, TC, Chimeh, F, Lu, Z, et al. "Factors that influence the cutaneous synthesis and dietary sources of vitamin D." Arch Biochem Biophys. 460 (2007) 213-7.
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