How many hours fasting for blood test

If your healthcare provider has instructed you to fast before your upcoming test, it means that you should not eat or drink anything besides water for the specified amount of time before having your blood drawn. Understanding why fasting is important and how to properly fast before a blood test can be helpful for eliminating pre-test anxiety and simplifying the testing process.

Below, learn how to fast for a blood test correctly to help make sure that your test results are accurate. Fasting before a blood test helps improve the accuracy and reliability of the test. Accurate test results are a critical component of diagnosing various health conditions and monitoring the effectiveness of treatment plans.

Your diet contains a range of nutrients, including carbohydrates, proteins, fats, minerals and vitamins. When you eat and drink normally, those nutrients are broken down and absorbed into your bloodstream.

If you take medications, continue taking them as normal unless your doctor says otherwise. Food and drinks can affect your results because sugar, fats, enzymes, minerals and cholesterol all absorb into your blood stream. Affected results could then lead to an inaccurate diagnosis. If you forget and eat or drink something, call your doctor or lab and ask if the test can still be done.

They can then tell you if you need to reschedule your test. Be honest with your doctor or lab technician if you mistakenly ate or drank. Most fasting lab results are available for your doctor in about 24 hours. However, some tests may take longer to complete.

That could affect the results of certain types of blood tests. Glucose tests are used to diagnose diabetes. You usually need to fast for 8—12 hours before a test. Most tests that require fasting are scheduled for early in the morning. That way, most of your fasting time will be overnight. Juice, coffee, soda, and other beverages can get in your bloodstream and affect your results.

In addition, you should not :. But you can drink water. It's actually good to drink water before a blood test. It helps keep more fluid in your veins, which can make it easier to draw blood. Ask your health care provider. Most of the time it's OK to take your usual medicines, but you may need to avoid certain medicines, especially if they need to be taken with food. Home Common health questions Operations, tests and procedures Back to Operations, tests and procedures.

Can I eat and drink before having a blood test? Common fasting blood tests Examples of blood tests that may require you to fast include: a fasting blood glucose test used to test for diabetes — you may be asked to fast for 8 to 10 hours before the test an iron blood test used to diagnose conditions such as iron deficiency anaemia — you may be asked to fast for 12 hours before the test For more information about a wider range of blood tests, go to Lab Tests Online.