USA Today is reporting that testing for vitamin D levels, once uncommon, has skyrocketed as medical studies raise awareness about vitamin D deficiencies. Physicians agree that they’re increasingly using the blood test to find out whether their patients are low on the vital vitamin.
My Take?
The jump in vitamin D testing comes after a slew of emerging research, much of it reported in this column, linking vitamin D deficiency with some infectious diseases, cancers, cardiovascular disease, fractures, osteoporosis, and autoimmune disorders.
In addition, research indicates that many Americans are deficient in vitamin D, and that is also fueling the testing trend.
Though specialists who treat bone-related conditions and the elderly regularly run D tests, now even we primary-care physicians are ordering the tests in children, teens, and adults.
A normal vitamin D test result is 30 ng/mL (nanograms/milliliter) or above. If a reading dips below that, a patient is considered insufficient; under 20 ng/mL, and he or she is tagged deficient. 
Indeed, levels can be enhanced with D-rich foods, such as fortified no-fat milk. But, many teens and adults don’t get enough.
The UV rays in sunshine also activate one form of vitamin D in the body, but increased sun exposure can lead to skin cancer.
So, what do I recommend? If your doctor tests your vitamin D level, and finds it low, I’d recommend a supplement.