What Is a Cortisol Test? A cortisol test measures the level of cortisol in your blood, urine or saliva. Cortisol is a hormone that's important throughout the body for maintaining blood pressure, blood ...

A BUN test measures the level of urea nitrogen in the blood using a standard blood sample. Abnormal BUN levels may indicate problems with liver or kidney functioning. BUN stands for blood urea ...

A complement C4 (also known as a complement component 4, or simply C4) is a test to measure the level of C4 proteins you have in your blood. These proteins play a role in how your immune system ...

Your potassium levels can indicate underlying health conditions like high blood pressure or kidney disease. A doctor may perform a potassium blood test as part of a routine physical. A potassium test ...