Understanding Your Laboratory Test: What It Is, Why It Is Done, and What to Expect

This laboratory test measures specific substances in a sample of your blood, urine, or other body tissue. The results help your healthcare provider evaluate how well your body is functioning and look for signs of illness or disease.

The 16-Beta,18-Dihydroxydeoxycorticosterone (16β,18-DiOH-DOC) urine test measures the amount of a specific corticosteroid metabolite in your urine. This substance is produced when your body breaks down deoxycorticosterone (DOC), a hormone made by the adrenal glands located on top of your kidneys. The test helps healthcare providers understand how well your adrenal glands are functioning and whether there are any abnormalities in corticosteroid production.

Your provider may order this test as part of a routine checkup, to help find the cause of symptoms you are having, to monitor an ongoing health condition, or to check how well a current treatment is working over time.

Your doctor may order this test if you have symptoms suggesting an adrenal gland disorder, such as unexplained weight changes, high blood pressure, excessive hair growth, acne, irregular periods, or signs of hormonal imbalance. It is particularly useful in diagnosing conditions like congenital adrenal hyperplasia (a genetic disorder affecting adrenal hormone production) and certain adrenal tumors that cause overproduction of corticosteroids.

A trained healthcare professional will collect a small sample for testing, most often a blood sample drawn from a vein in your arm with a sterile needle. Sometimes a urine sample, throat swab, or other specimen is collected instead and sent to a laboratory for analysis.

This test requires a 24-hour urine collection. You will be given a special container to collect all urine produced over a 24-hour period. During collection, it's important to follow instructions carefully: store the container refrigerated or on ice, avoid contaminating the sample with toilet paper or feces, and collect the first-morning urine separately. After the 24-hour period, return the container to your healthcare provider's office or laboratory as instructed.

This test is very safe. You may feel a quick sting when the needle is placed and notice mild bruising afterward. Follow any special instructions from your provider, such as fasting for a set number of hours beforehand, and tell them about all medicines and supplements you take.

There are no significant risks associated with this test beyond those of routine urine collection. You may need to avoid certain medications, supplements, or foods that could affect test results—your healthcare provider will give you specific instructions. Inform your doctor about all medications you are taking, as some drugs can interfere with corticosteroid measurements. It is helpful to drink normal amounts of fluids during the collection period unless otherwise directed.