The Cortisol Serum (3 to 5 PM) test is a diagnostic blood test that measures the level of cortisol, a hormone produced by the adrenal glands, in the blood. Cortisol plays an important role in the body’s stress response and helps regulate metabolism, blood pressure, and immune system function. The test is typically performed in the late afternoon, as cortisol levels naturally decrease throughout the day. Abnormal levels of cortisol in the blood can indicate underlying health conditions, such as Cushing’s syndrome, Addison’s disease, or adrenal gland dysfunction. Symptoms of these conditions can include weight gain, high blood pressure, and fatigue. The Cortisol Serum (3 to 5 PM) test is a useful tool for diagnosing and monitoring these conditions and can help guide treatment decisions. However, it’s important to note that cortisol levels can also be affected by medications and other factors, such as stress, so additional testing may be needed to confirm a diagnosis.