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Health Information For Teens
A blood test is when a sample of blood is taken from the body to be tested in a lab. Doctors order blood tests to check things such as the levels of glucose, hemoglobin, or white blood cells. This can help them find problems like a disease or medical condition. Sometimes, blood tests can help them see how well an organ (such as the liver or kidneys) is working.
A complete blood count (CBC) test is a blood test that helps doctors check the level of different types of cells in the blood. A CBC measures:
A CBC can be done as part of a routine checkup to screen for problems or because someone isn’t feeling well. The levels of red blood cells, white blood cells, and platelets can provide doctors with information about possible problems like anemia (low red blood cells), infections, inflammation, and other conditions.
You should be able to eat and drink normally unless also getting other tests that require fasting beforehand. Tell your doctor about any medicines you take because some drugs might affect the test results. Also let the doctor know if you have had a blood transfusion or if you smoke. These can also affect the CBC.
It can help to wear a T shirt or other short-sleeve top on the day of the test to make things faster and easier for the technician who will be drawing the blood.
Most blood tests take a small amount of blood from a vein. To do that, a health professional will:
It’s best to try to relax and stay still during the procedure because tensing muscles can make it harder and more painful to draw blood. And if you don’t want to watch the needle being inserted or see the blood collecting, you don’t have to. Look the other way and maybe relax by focusing on saying the alphabet backward, doing some breathing exercises, thinking of a place that makes you happy, or listening to your favorite music.
Most blood tests take just a few minutes. Occasionally, it can be hard to find a vein, so the health professional may need to try more than once.
The health professional will remove the elastic band and the needle and cover the area with cotton or a bandage to stop the bleeding. Afterward, there may be some mild bruising, which should go away in a few days.
Blood samples are processed by a machine, and it may take a few hours to a day for the results to be available. If the test results show signs of a problem, the doctor might order other tests to figure out what the problem is and how to treat it.
A CBC is a safe procedure with minimal risks. Some people might feel faint or lightheaded from the test. A few teens have a strong fear of needles. If you’re anxious, talk with the doctor before the test about ways to make the procedure easier.
A small bruise or mild soreness around the blood test site is common and can last for a few days. Get medical care if the discomfort gets worse or lasts longer.
If you have questions about the CBC, speak with your doctor or the health professional doing the blood draw.
If you’re afraid of shots, you’re not alone. Next time your doc asks you to roll up your sleeve, try these tips.
These videos show what’s involved in getting a blood test and what it’s like to be the person taking the blood sample.
Find out about the mysterious, life-sustaining fluid called blood.
Anemia is common in teens because they undergo rapid growth spurts, when the body needs more nutrients like iron. Learn about anemia and how it’s treated.
A basic metabolic panel (BMP) is a group of blood tests that provide doctors with clues about how the body is working. Find out why doctors do this and what’s involved for teens.
This group of blood tests provides doctors with clues about how the body is working. Find out why doctors do these tests and what’s involved for teens.
This test measures the speed at which red blood cells fall to the bottom of an upright glass test tube. Find out why doctors do it and what’s involved for teens.
Need to get a blood test? An MRI? These videos show what happens in 10 of the most common medical tests.
Visit our Cancer Center for teens to get information and advice on treating and coping with cancer.
Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.
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