Key Points

• 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.
• Blood tests are very common. When you have routine checkups, your doctor often orders blood tests to see how your body is working.
• Some of the most common types of blood tests that doctors order are complete blood count (CBC), blood chemistry tests, blood enzyme tests, and blood tests to assess heart disease risk.
  • A CBC can detect blood diseases and disorders.
  • Blood chemistry tests measure different chemicals in the blood. These tests give doctors information about nerves, muscles (including the heart), bones, and organs such as the kidneys and liver.
  • Blood enzyme tests measure the amounts of enzymes in your blood. These tests can help diagnose a heart attack.
  • Blood tests to assess heart disease risk measure chemicals in your blood that show whether you're at increased risk for heart disease.
• Many blood tests don't require any special preparation and take only a few minutes. Other blood tests require fasting (not eating any food) anywhere from 8 to 12 hours before the test.
• During a blood test, blood usually is drawn from a vein in your arm or other part of your body using a thin needle. It also can be drawn using a finger prick. Drawing blood usually takes less than 3 minutes.
• Once the needle is withdrawn, you'll be asked to apply gentle pressure with a piece of gauze or bandage to the place where the needle went in. This helps stop bleeding. After a minute or two, you can remove the pressure.
• The main risks with blood tests are discomfort or bruising at the site where the needle goes in. These complications usually are minor and go away shortly after the tests are done.
• Your doctor should get the results of your blood test(s) and discuss them with you. Blood tests show whether the levels of different substances in your blood fall within a normal range. Your doctor should discuss any unusual or abnormal results with you.