How Long to Fast Before a Blood Test

April 19, 2012

fasting for blood testIf you’ve been considering having some blood work done, you may be asking yourself “How long should you fast  before taking a blood test?” It’s true that it’s important to fast before blood tests in order to get the most accurate readings.  Anytime you eat, your body must process the nutrition as it travels throughout your bloodstream. When you undergo blood testing, a number of different components are examined including:

  • Blood contaminants
  • Foreign entities
  • Blood sugar levels
  • Foods consumed

When you eat too soon before any blood tests, you can severely skew the accuracy of your blood test results. Fast the correct amount of time before blood testing, to assist your physician in obtaining an accurate view of your body chemistry.

Which blood tests require fasting?

  • High density lipoprotein (HDL )
  • Fasting metabolic panel
  • Fasting lipid panel
  • Fasting glucose
  • Fasting cholesterol
  • Triglyceride

If you eat too soon before any of these blood tests, you’ll severely affect results. This can mean a waste of time and money for you and your doctor and possibly a compromise of your health.

How long should you fast before a blood test?

If your blood tests are ordered by your doctor, he or she will tell you exactly how long you should fast. If you take advantage of online blood testing from Lab Test Portal, the information you receive when you purchase the blood tests you want will provide this information. Talk with Lab Test Portal’s friendly and knowledgeable staff if you have questions.

Generally speaking, you should fast for 6 to 12 hours before blood testing. That‘s why it’s a good idea to schedule your blood tests first thing in the morning. You can naturally fast overnight as you sleep, and treat yourself to breakfast after your blood testing is done!

What are some specific times to fast before blood testing?

Glucose test: 8 hours. It is important for your body to be well-rested and free of outside influences for glucose testing.  Schedule your glucose blood work test first thing in the morning before you eat and while you’re still rested and refreshed.

Cholesterol blood test: 12 hours. To get an accurate triglyceride reading, fast for 12 hours before cholesterol testing. Avoid the cholesterol testing offered at health fairs and mall kiosks. These types of tests are never accurate and can lull you into a false sense of security or cause unnecessary alarm.

What is the best way to fast before blood testing?

1. Be sure to drink lots of water and stay well hydrated unless otherwise directed by your doctor via an NPO (nothing by mouth) order.
2. Continue to take your prescribed medications unless otherwise directed by your doctor.
3. Abstain from smoking during your fasting time.
4. Do not chew gum during your fast

How hard is it too fast before blood testing?

Fasting before blood testing is not difficult, especially if you can fast overnight while you sleep. Remember to follow these steps to fast correctly before blood testing:

* Ask your doctor or the lab staff how long you must fast for the specific blood testing you plan to have. Remember that in some cases you will fast only for 6 hours. In others, you may fast for as long as 8 to 12 hours.

* Make fasting easy for yourself by scheduling your blood testing first thing in the morning. Simply stop eating after dinner (6 to 7 PM) go to bed early, go straight to the lab when you get up, have your blood test and go out for breakfast!

* If you are planning on having a blood cholesterol test to qualify for a life insurance policy, eat properly in the weeks before the test. Keep away from high cholesterol and high fat foods such as eggs and red meats.

* If you are simply getting routine blood work, continue with your regular diet before blood testing and up until the time your fast begins. This helps your doctor see your normal blood cholesterol levels.

* Remember to ask your doctor or the lab staff about beverages. Usually, you are encouraged to drink plenty of pure water. Sometimes, you are allowed to drink clear beverages such as coffee and tea; however, you must be sure to ask about this.
* If you have cheated on your fast, be sure to inform the staff at the lab. This is very important knowledge to be used in interpreting the results of your blood tests.

Clearly, “How long to fast before a blood test?” Is a question that has more than one answer. Follow the guidance presented here and that of your doctor and the staff at blood testing resources such as to fast for just the right amount of time and get accurate blood test results.

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3 Responses to How Long to Fast Before a Blood Test

  1. Bonnie Virag on December 10, 2012 at 9:24 am

    Very informative and detailed Fasting requirements. Best one I found. Enjoy the Holidays!


  2. Bonnie Virag on December 10, 2012 at 9:25 am

    Very informative and detailed fasting requirements. Best one I read. Enjoy the Holidays!

  3. Peter Marks on December 18, 2012 at 6:54 am

    On your website you ask “How hard is it too fast before blood testing?”
    I guess you mean “to fast” NOT “…too fast”
    It becomes hard to trust clinical diagnosis when the company seems spell challenged.
    Have a blessed Christmas.

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