A vitamin D test is a blood test that measures the level of vitamin D (calciferol) in your blood. It can indicate whether the vitamin D levels in your body are low or high. Low vitamin D levels can ...

Some vitamin D tests may give misleading results despite progress made in recent years to improve the quality of these assays, according to the US Centers for Disease Control and Prevention (CDC).

Vitamin D tests certified by the U.S. Centers for Disease Control and Prevention (CDC) Clinical Standardization Programs (CSP) are well calibrated overall, according to a new study presented Sunday at ...

Historically, 400 IU (10 ug) of vitamin D was recommended for better health because it closely approximated the amount of vitamin D in a teaspoonful of cod liver oil. However, 800 to 1,000 IU is the ...