how many hours should you fast before doing blood work?
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You usually need to fast for 8–12 hours before a test.
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Tell your doctor about any prescription or over-the-counter medications or supplements you're taking. You may need to fast (refrain from eating or drinking) for four hours before the test.
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However, fasting is required before commonly ordered tests for glucose (blood sugar) and triglycerides (part of the cholesterol, or lipid, panel) for accurate results. You should not eat for eight hours before having your blood glucose measured to check for diabetes or to see how well treatments are working.
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How do you prepare for a blood test? Some blood tests will require you to fast beforehand. In these cases, your doctor will instruct you not to eat or drink anything, except water, in the hours leading up to the test.
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Patient Instructions If your doctor has requested that a fasting blood test be performed, fasting is generally overnight. 12 hours is the optimal fasting period. Fasting longer than the recommended time could compromise your results. You may be advised to defer the test to another day.
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For these tests, most hospital departments or radiology practices will ask you to fast (not eat or drink) before your appointment. Fasting for 2–4 hours is common, and it is usually permitted to drink water over this time to avoid dehydration (losing too much water from your body).
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How long do I have to fast before the test? You usually need to fast for 8–12 hours before a test. Most tests that require fasting are scheduled for early in the morning.
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You should fast for 8 hours before having an iron level blood test. This is to ensure that levels of iron detected in your blood are not skewed by food or drink intake.
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Typically, people will be asked to fast for 10 to 12 hours before having one of these tests. Renal function panel: Tests to see how well the kidneys are working. Typically, people are asked to fast for 8 to 12 hours before these tests. Vitamin B12 test: Tests for the levels of the vitamin B12 in a person's blood.
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Requirements Prior to the Test You are to remain on a normal, unrestricted diet for at least 3 days prior to test. You have had no acute significant illness for 2 weeks prior to test. Fasting is required for a period of 8-10 hours prior to the test. (No food or fluids such as tea, coffee or fruit juice.)
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This means that you should consume no food or drink (except plain water) for at least 12 hours before the blood test. Please DO continue to take any prescribed medication with water only. It is possible to perform the blood test if you have not fasted.
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With certain blood tests, you may be instructed to fast for up to eight hours before your appointment. Fasting before a blood draw means you don't eat or drink anything except water. Don't wait until the day of your blood draw to ask if you should fast.
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How often and when should I test? You may need to test your blood several times a day. Generally, these times are fasting (first thing in the morning before you eat) and 2 hours after each meal. Occasionally, you may be asked to test more frequently during the day or at night.
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You may be instructed not to eat or drink anything except water for 9 to 12 hours before having your blood drawn. This is called a "fasting blood test." Fasting is not always necessary, but it may be recommended.
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How long should you fast before a blood test? The amount of time you need to fast for will vary depending on the test. For most tests, you will be told not to consume anything but water for eight hours leading up to the test. For a few tests, a 12-hour fast may be needed.
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#13 – Fast 24 Hours Before Your Exam You can get the most accurate results by fasting for about 24 hours before the exam. That way, you don't throw numbers off by having a blood sugar spike or increased blood pressure due to an unhealthy meal.
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With certain blood tests, you may be instructed to fast for up to eight hours before your appointment. Fasting before a blood draw means you don't eat or drink anything except water.