Complete Blood Count (CBC)

A complete blood count (CBC) is a common blood test that measures the cells circulating in your blood, including red blood cells, white blood cells, and platelets. It gives your doctor a broad picture of your overall health and helps detect conditions such as infections, anemia, and other blood disorders.

This test measures the level of 17-hydroxyprogesterone (17-OHP) in your blood. It is specifically the third blood sample collected after you receive a dose of gonadotropin releasing hormone (GnRH). This is called a GnRH stimulation test, which helps doctors evaluate how well your adrenal glands are working.

Your doctor may order this test as part of a routine checkup, to look into symptoms like fatigue, weakness, fever, unexplained bruising, or frequent infections, or to monitor a condition you already have and track how well your treatment is working over time.

Your doctor may order this test if they suspect you have a condition affecting your adrenal glands, such as congenital adrenal hyperplasia (CAH). CAH is a genetic disorder that affects the adrenal glands' ability to produce certain hormones. The GnRH stimulation test helps doctors see how your adrenal glands respond to hormone signals and can differentiate between normal and abnormal adrenal function.

A healthcare professional will draw a small sample of blood, usually from a vein on the inside of your elbow or the back of your hand, using a thin needle. The collection takes only a few minutes, and the sample is sent to a laboratory where the number, size, and type of your blood cells are measured.

A healthcare professional will first give you an injection of GnRH. Then, they will collect blood samples at specific time intervals - typically at baseline (before the injection), and then at 15, 30, 60, and/or 120 minutes after the injection. The '3rd specimen' refers to the third blood sample taken after receiving the GnRH dose. Blood is drawn from a vein in your arm using a small needle.

This test usually requires no special preparation, and you can normally eat and drink beforehand. If the CBC is ordered together with other blood tests that require fasting, your doctor will let you know. Mention any medications or supplements you take, since some of them can affect the results.

Follow your doctor's instructions about any special preparations. You may need to fast (not eat or drink anything except water) for a certain period before the test. Inform your doctor about all medications you are taking, as some medicines can affect the test results. Wear comfortable clothing with sleeves that can be easily rolled up.

This test is very safe. You may feel a quick sting when the needle is inserted, and the puncture site can be slightly sore, red, or bruised for a day or two. Serious problems such as infection or heavy bleeding are rare. Tell your provider beforehand if you have a bleeding disorder or take blood thinners.

The risks are minimal and include slight pain or bruising at the injection site, dizziness, or rare infection. The GnRH injection may cause temporary flushing, headache, or nausea. These side effects are usually mild and go away quickly.