Nearly everyday here in sunny Tacoma, WA, I am asked by a patient to check their vitamin D levels. At our hospital, the vitamin D test is one of the most commonly ordered and most expensive tests. In fact, patients could literally purchase a 5 year supply of supplemental vitamin D for the cost of one vitamin D test per our chief lab officer. So why all the fuss with vitamin D? The issue is a matter of association and observational studies. Vitamin D isnt just a vitamin, it is a hormone that is absolutely necessary for humans. Studies have demonstrated an association between vitamin D and various cancers, heart disease, bone and musculosketal disorders, asthma, and depression along with numerous other conditions. The issue of course is that association doesnt ensure causation and numerous randomized controlled trials of vitamin D supplementation for many of the above listed conditions have not been conclusive (asthma, cancer) or were negative studies (sickle cell, infections, osteoarthritis, wheezing, postmenopausal women, chronic pain, hypertension, depression). The best data for vitamin D is for prevention of falls, strengthening bones, and breastfed infants. This hasnt stopped patients from asking to be tested and providers complying. Choosing Wisely even has a recommendation in an attempt to stop the madness. If patients are determined to know their levels and track their intake, is there an app to help them?

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