Blood Testing

What Is It?

Blood tests enable doctors to assess your health by analyzing cells, chemicals, proteins and other substances in your blood. Some tests are recommended regularly to see if blood levels of certain cells or chemicals fall within a normal range. Others are done to help diagnose health conditions, such as allergies, anemia, and diabetes.

There are two typical methods for taking a blood sample. One, called venipuncture, involves drawing a vial of blood from a vein, usually on the inner surface of your arm near your elbow. The other, called a finger stick, is done by pricking your finger with a sharp blade to obtain a small amount of blood from a capillary. The method used depends on how much blood is needed for the test you are having.

What It's Used For

Blood tests can be used to screen for a wide variety of diseases and disorders. They are also used to determine how well treatment is working for many different conditions. The kinds of problems for which doctors order blood tests include:

To continue reading this article, you must login.
  • Research health conditions
  • Check your symptoms
  • Prepare for a doctor's visit or test
  • Find the best treatments and procedures for you
  • Explore options for better nutrition and exercise
Learn more about the many benefits and features of joining Harvard Health Online »