What is a Blood Test?

• A blood test is a procedure in which a thin needle is inserted, usually on the inside of your arm, and blood is "drawn" out through the needle into a syringe. It is one of the routine ways your doctor can determine what may be wrong with you, or to make sure your body is functioning properly.
  
  

Why a Fasting Blood Test?

• Some blood tests will not be accurate if you eat or drink before the test.
  
  

What Kinds of Blood Tests Require Fasting?

• Some of the tests that may require fasting are tests for cholesterol, glucose and iron in the blood. Tests for HIV, hepatitis A or B, and cancer also may require you to fast before having blood drawn.
  
  

Drinking and Eating Before Your Blood Test

• You will be asked not to have anything by mouth anywhere from 8 to 12 hours before your test. In this case, some laboratories may allow water, but never food, coffee, tea, alcohol or fruit juice.
  
  

Risks of Blood Tests

• There is not much risk involved in having a blood test, but bruising may occur. If this happens, make sure you apply firm pressure to the site for a few minutes. The other risk is there may be some discomfort at the place where your blood was drawn. These are both temporary conditions that will soon go away.