Blood Tests: An Overview
Red blood cells are biconcave, disc-shaped cells that transport oxygen from the lungs to body cells. They circulate around the body in the blood and also remove carbon dioxide to the lungs for exhalation. Their red colour comes from the oxygen-carrying protein haemoglobin. Red blood cells are the most abundant cell in the blood. They have no nucleus and are about 7 micrometres in diameter. Magnification: x1650 when printed 10 centimetres wide.
Blood tests are very common. When you have routine checkups, your doctor may recommend blood tests to see how your body is working.
Many blood tests don’t require any special preparations. For some, you may need to fast (not eat any food) for 8 to 12 hours before the test. Your doctor will let you know how to prepare for blood tests.
During a blood test, a small amount of blood is taken from your body. It’s usually drawn from a vein in your arm using a needle. A finger prick also may be used. The procedure usually is quick and easy, although it may cause some short-term discomfort. Most people don’t have serious reactions to having blood drawn.
Lab workers draw the blood and analyze it. They use either whole blood to count blood cells, or they separate the blood cells from the fluid that contains them. This fluid is called plasma or serum.
The fluid is used to measure different substances in the blood. The results can help detect health problems in early stages, when treatments or lifestyle changes may work best.
However, blood tests alone can’t be used to diagnose many diseases or medical problems. Your doctor may consider other factors, such as your signs and symptoms, your medical history, and results from other tests and procedures, to confirm a diagnosis.
Blood tests help doctors check for certain diseases and conditions. They also help check the function of your organs and show how well treatments are working.
Specifically, blood tests can help doctors:
- Evaluate how well organs, like the kidneys, liver, and heart, are working
- Diagnose diseases and conditions such as cancer, HIV/AIDS, diabetes, anemia (uh-NEE-me-eh), and coronary heart disease (also called coronary artery disease)
- Learn whether you have risk factors for heart disease
- Check whether medicines you’re taking are working
Blood tests have few risks. Most complications are minor and go away shortly after the tests are done.
Source: National Heart, Lung and Blood Institute