The only way to know if you're getting enough vitamin D is to get testedeither by your doctor (a simple, standard blood test) or by yourself: ZRT Laboratory provides an easy-to-use, relatively painless home test ($75; zrtlab.com). The results might surprise you. Case in point: Here's how several Outside editorsoutdoor junkies in sunny Santa Fe, New Mexicoand our writer in Chicago fared at the end of winter:
MONIQUE RYAN, WRITER // CHICAGO,51*
ABE STREEP, SENIOR EDITOR // SANTA FE,33
JUSTIN NYBERG, ASSOCIATE EDITOR // SANTA FE, 31
CHRISTOPHER KEYES, EDITOR // SANTA FE,24
RYAN KROGH, RESEARCH EDITOR // SANTA FE,20
U.S. AVERAGE IN WINTER 15-18
*Supplementing with 1,200 IU of vitamin D daily. It takes about 1,000 IU to raise blood levels by 10 units.
SOURCE: ZRT LAB TESTS; THE VITAMIN D SOLUTION, BY MICHAEL HOLICK
UNITS: NANOGRAMS OF VITAMIN D PER MILLILITER OF BLOOD (NG/ML)
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