Vitamin D Level

25-hydroxyvitamin D measurement to assess vitamin D status.

A vitamin D test measures the level of 25-hydroxyvitamin D in your blood — the most accurate indicator of your body's vitamin D status. Vitamin D is essential for calcium absorption, bone health, immune function, and mood regulation. Despite its importance, vitamin D deficiency is one of the most common nutritional deficiencies worldwide, affecting an estimated 1 billion people. Low levels are linked to increased risk of osteoporosis, fractures, autoimmune diseases, depression, and certain cancers. People living at higher latitudes, those with darker skin, office workers with limited sun exposure, and the elderly are particularly at risk.