Dr. Holick describes the only test that can indicate if a woman is vitamin D deficient.
The only test that I will tell you if you are vitamin D deficient is the 25-hydroxy vitamin D. And what you care about is the total 25-hydroxy vitamin D because there are many different laboratories doing these tests and some will give 25-hydroxy D2 and the 25-hydroxy D3, and people and doctors don’t know what to do about that. All you care about is the total, and what we want it to be is at least 30 nanograms/ml.
And it’s also important to realize that even if your doctor says that the active form of vitamin D is probably a better indicator, it is not; 1,25-dihydroxy vitamin D is normal or elevated when you are vitamin D deficient.
About Dr. Holick, Ph.D., M.D.:
Michael Holick, Ph.D., M.D., is the Professor of Medicine of Physiology and Biophysics at Boston University School of Medicine. He received his medical degree from the University of Wisconsin, Madison and performed his residency and fellowship at Massachusetts General Hospital. Dr. Holick specializes in vitamin D, calcium, bone metabolism, photobiology of vitamin, and osteoporosis. Dr. Holick is also the recipient of the American Skin Associations Psoriasis Research Achievement Award, the American College of Nutrition Award, the Robert H. Herman Memorial Award in Clinical Nutrition from the American Society for Clinical Nutrition, and more.