Vitamin D deficiency is a condition in which your body ... Your liver converts vitamin D into 25 hydroxyvitamin D, or 25(OH)D. Your kidneys use 25(OH)D to make "active vitamin D," which helps ...
Despite the importance of vitamin D for overall health, it is estimated that about one billion people worldwide have a deficiency, usually defined as having serum levels of 25-hydroxyvitamin D 3 ...
Additionally, frequent illnesses or infections can indicate a compromised immune system, which can be linked to low vitamin D levels. The most reliable method, however, is a blood test. A healthcare ...