Your blood contains different kinds of cells in a clear fluid called plasma. Blood carries nutrients (from your digestive system) and hormones (from your glands) to cells throughout your body. It also carries waste to your excretory system (the system that gets rid of what your body doesn’t need). And blood can carry germs all through your body when you get an infection.
Testing your blood to see how many of each kind of cell you have can show whether there are any problems. Some drugs you may be taking can affect these tests. Your doctor may suggest you stop using a certain drug to see if it is the cause. Your blood cells are produced in your bone marrow. Several drug treatments used for HIV infection can affect bone marrow, which in turn can affect the levels of many of these cells.
Complete blood count (CBC): This is made up of several different tests. These are the most common blood tests, and they’re done quite often. Your CBC can give you and your doctor a general sense of your overall health. Any count that is outside your normal range can suggest an infection or damage to your body, which tells your doctor to go on to do more specific tests. Your CBC studies three different kinds of cells: white blood cells, red blood cells, and platelets.
White blood cell (WBC) count: White blood cells (also called leukocytes are your immune system cells. This test measures the total number of white blood cells found in a sample of your blood. A low white blood cell count is called leukopenia. AZT, ganciclovir, and other medications can cause a drop in the number of your white blood cells. If you take these drugs, your doctor will probably monitor your WBC count every month.
Differential: This test breaks down the WBC into different types of white blood cells and tells you what percentage of them are lymphocytes, macrophages , or other kinds of cells. Increases or decreases in the numbers of these cells can show different types of problems. You can discuss these issues with your doctor.
Red blood cell (or RBC) count: Red blood cells give blood its red colour, which comes from iron. They carry oxygen from your lungs to all the other cells in your body. They also carry carbon dioxide from your tissues to your lungs, where it’s breathed out. This count tells you how many red blood cells there are in a certain amount of blood.
Hemoglobin (Hgb): Red blood cells contain hemoglobin, which binds to oxygen in your lungs and carries it to tissues all through your body, where it’s released. Even if you have enough red blood cells, you may not have enough hemoglobin.
Hematocrit: Your blood is made up of plasma and red blood cells, white blood cells, and platelets (see below). The hematocrit measures the percentage of your blood that is made up of all these cells except the plasma.