You were told to fast before your blood test, but your appointment isn’t until 3 pm and you are starving. Will it really make a difference?
For some tests, yes it actually will.
Fasting for a blood glucose test is important, because this test can help diagnose diabetes. It is important that a patient has not had anything to eat or drink for 8-10 hours before the test, to ensure an accurate blood glucose level test to rule out diabetes.
Fasting is also important for cholesterol testing. Cholesterol is a type of fat in our blood. If a patient has eaten a meal before the test, the results will be skewed. It is important not to eat for 8-10 hours before this test as well.
Not fasting before a blood test can also affect blood iron testing to evaluate for anemia.
Fun fact: Smoking or drinking alcohol before a blood test can cause liver function tests to be abnormal. It is best not to smoke or drink alcohol for 24 hors before liver function testing.