What determines if I should get it done? Get answers to the most asked questions about routine blood work. Blood can tell you about your organ function, diet, metabolism, illnesses, and if you have certain diseases.
It can tell you hundreds of things about your lifestyle and habits. You likely have lots of questions about the process and results.
Keep reading for everything you need to know about blood tests. Usually, the technician, nurse, or doctor will have you sit down on a chair with your feet on the ground. This is often inside your forearm where the veins are visible. But, they can take it from any vein. Then, a needle attached to a test tube is inserted. In some cases, they may need to collect more than one tube before taking out the needle.
The reasons for getting your blood tested vary. In a routine blood test, it might just be to check that nothing has changed since your last healthy test result. This routine blood test measures the cells in the body through the blood. They test the blood for white blood cells, red blood cells, hemoglobin, hematocrit, and platelets. CBC tests can detect if you have anemia, nutritional deficiencies, an infection, cancer, and bone marrow problems. This blood test measures certain components of the blood.
The first screening test for a condition often has to be confirmed by a second, more specific test to find out whether the results are accurate and meaningful for your health. An example is the rapid HIV test, which is often accurate but rarely will cause a false positive meaning the test result is positive, but the person does not actually have the disease. This can occur with certain tests that measure antibodies, since a person may have an immune condition such as rheumatoid arthritis or multiple myeloma that also produces antibodies and interferes with the test.
For example, if you had a blood test for hepatitis C and the results came back negative, but you were exposed to the virus in the past few months, you could still have an infection and not realize it. A test result outside the normal range of expected lab values does not necessarily mean you have a disease or disorder. Test results can be abnormal for other reasons. If you had a fasting plasma glucose test and you ate something before the test, or were drinking alcohol the night before or taking certain medications, your results could be temporarily outside the normal ranges, but are not evidence of a disease.
To avoid such problems, it is best to talk with your doctor before any lab tests about whether you need to make any special preparations before getting your blood drawn, such as fasting the night before.
Although mix-ups of blood test samples are rare, they do happen. How your blood sample is handled before it's analyzed can affect results, too. For example, if the sample is collected in the wrong container, shaken inappropriately, or stored for too long or at the wrong temperature, you may get an erroneous result. The main risks of blood tests are discomfort and bruising at the site where the needle goes in. These complications usually are minor and go away shortly after the tests are done.
Blood tests show whether the levels of different substances in your blood fall within a normal range. For many blood substances, the normal range is the range of levels seen in 95 percent of healthy people in a certain group. For many tests, normal ranges vary depending on your age, gender, race, and other factors.
Your blood test results may fall outside the normal range for many reasons. Abnormal results might be a sign of a disorder or disease. Other factors—such as diet, menstrual cycle, physical activity level, alcohol intake, and medicines both prescription and over the counter —also can cause abnormal results.
Your doctor should discuss any unusual or abnormal blood test results with you. These results may or may not suggest a health problem. Many diseases and medical problems can't be diagnosed with blood tests alone. However, blood tests can help you and your doctor learn more about your health. Blood tests also can help find potential problems early, when treatments or lifestyle changes may work best.
NOTE: All values in this section are for adults only. They don't apply to children. Talk to your child's doctor about values on blood tests for children. The table below shows some normal ranges for different parts of the complete blood count CBC test. Some of the normal ranges differ between men and women. Other factors, such as age and race, also may affect normal ranges. Your doctor should discuss your results with you.
He or she will advise you further if your results are outside the normal range for your group. This table shows the ranges for blood glucose levels after 8 to 12 hours of fasting not eating. It shows the normal range and the abnormal ranges that are a sign of prediabetes or diabetes. The table below shows ranges for total cholesterol, LDL "bad" cholesterol, and HDL "good" cholesterol levels after 9 to 12 hours of fasting.
High blood cholesterol is a risk factor for coronary heart disease. He or she will advise you further if your results are outside the desirable range. Learn more about participating in a clinical trial. View all trials from ClinicalTrials. Visit Children and Clinical Studies to hear experts, parents, and children talk about their experiences with clinical research.
Blood Tests. What Are Blood Tests? Outlook Blood tests have few risks. Types - Blood Tests. It's often done as part of a routine checkup. Red Blood Cells Red blood cells carry oxygen from your lungs to the rest of your body. White Blood Cells White blood cells are part of your immune system, which fights infections and diseases.
Hemoglobin Hemoglobin HEE-muh-glow-bin is an iron-rich protein in red blood cells that carries oxygen. Hematocrit Hematocrit hee-MAT-oh-crit is a measure of how much space red blood cells take up in your blood. Blood Glucose Glucose is a type of sugar that the body uses for energy. Calcium Calcium is an important mineral in the body.
Electrolytes Electrolytes are minerals that help maintain fluid levels and acid-base balance in the body. Blood Enzyme Tests Enzymes are chemicals that help control chemical reactions in your body. Troponin Troponin is a muscle protein that helps your muscles contract. A lipoprotein panel gives information about your: Total cholesterol.
LDL "bad" cholesterol. This is the main source of cholesterol buildup and blockages in the arteries. For more information about blockages in the arteries, go to the Diseases and Conditions Index Atherosclerosis article.
HDL "good" cholesterol. This type of cholesterol helps decrease blockages in the arteries. Triglycerides are a type of fat in your blood. Most people will need to fast for 9 to 12 hours before a lipoprotein panel. What To Expect During Blood Tests Blood usually is drawn from a vein in your arm or other part of your body using a needle. Drawing blood usually takes less than 3 minutes. What To Expect After Blood Tests Once the needle is withdrawn, you'll be asked to apply gentle pressure with a piece of gauze or bandage to the place where the needle was inserted.
What Are the Risks of Blood Tests?
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