Complete Blood Count (CBC)

The complete blood count, known as the CBC, is a routine blood test that measures the cells circulating in your blood, including red blood cells, white blood cells, and platelets, and helps your healthcare provider assess your overall health as well as detect or monitor many different disorders.

The 17-Hydroxyprogesterone (17-OHP) test measures the amount of a specific hormone in your blood. This test is done twice: once before and once 15 minutes after receiving an injection of ACTH (adrenocorticotropic hormone), which is also called a cosyntropin or Cortrosyn stimulation test. The ACTH injection stimulates your adrenal glands to produce hormones, and this test helps doctors see how well your adrenal glands respond.

Your provider may order this test as part of a routine checkup, to investigate symptoms such as fatigue, weakness, fever, unusual bruising, or bleeding, to monitor an existing condition such as anemia or infection, or to track how a treatment you are receiving is affecting your blood cells.

This test is primarily used to diagnose and evaluate conditions affecting the adrenal glands, especially congenital adrenal hyperplasia (CAH). CAH is a genetic disorder that affects the adrenal glands' ability to produce certain hormones. The test can also help distinguish between different types of adrenal disorders and evaluate adrenal gland function.

This test usually requires no special preparation, and you can typically eat and drink normally beforehand. Tell your provider about all medicines, vitamins, and supplements you take, because some can affect the results. If your sample will be used for other tests at the same time, you may be asked to fast for several hours, and you will receive specific instructions if that applies to you. Wearing a sleeve that rolls up easily can make the visit more comfortable.

Your doctor will provide specific instructions. Generally, you may need to fast (not eat or drink) for a certain period before the test. Inform your doctor about all medications you are taking, as some medications can affect test results. Women should tell their doctor about their menstrual cycle, as hormone levels can vary during the cycle.

A trained professional will wrap an elastic band around your upper arm, clean the skin at the inside of your elbow or the back of your hand, and insert a small needle into a vein to collect the sample into a tube. You may feel a brief pinch or sting, and the collection usually takes only a few minutes. After the needle is removed, pressure and a small bandage are applied to the site, and you can return to your normal activities right away.

A healthcare professional will first draw a blood sample from a vein in your arm. Then, you will receive an injection of ACTH (cosyntropin). After exactly 15 minutes, another blood sample will be drawn. The process usually takes about 30-45 minutes total. You may experience mild discomfort during the blood draw.

Your report will show whether your red blood cell, white blood cell, and platelet levels fall within the standard reference ranges listed beside each result. Values that are higher or lower than normal can point to conditions such as anemia, infection, inflammation, or clotting problems, but a single abnormal value does not always mean you are ill. Your provider will interpret your numbers together with your symptoms, medical history, and other test results, so review the report with them before drawing any conclusions.

Normal results vary based on age, sex, and laboratory reference ranges. Significantly elevated 17-OHP levels after ACTH stimulation typically indicate congenital adrenal hyperplasia. Your doctor will interpret your results in context with your symptoms and other test findings.