how many hours do you fast for a blood test?
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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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If fasting is required, you should not have anything to eat or drink (with the exception of water) for 10–12 hours before your test. Unless advised by your doctor, you should take all regular medication.
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For these blood glucose tests used to diagnose diabetes, you must fast at least 8 hours before you have your blood drawn. If you have symptoms of diabetes, your doctor may use the random plasma glucose test, which doesn't require fasting.
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It depends on the test. Fasting for a lab test typically lasts eight hours. Your doctor should give you any special instructions related to your tests, including fasting requirements.
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How to prepare for a blood glucose test. Blood glucose tests are either random or fasting tests. For a fasting blood glucose test, you can't eat or drink anything but water for eight hours before your 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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How long do I have to fast before the test? 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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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. If you're having a blood test for ferritin levels – a measure of how much iron is stored in the body – you don't usually need to fast before.
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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. Usually, you are allowed to take your medicines with water the morning of the test.
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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.
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Vitamin B12 test: Tests for the levels of the vitamin B12 in a person's blood. Typically, people are asked to fast for 6 to 8 hours for these tests. They must also let the doctor know what medications they take, as some can interfere with the test.
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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.
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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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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.) You may have sips of water if you are thirsty. Due to the nature of the test, testing is generally done in the morning.
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You will be asked to come to the test fasting — not having had anything to eat or drink for the previous eight hours. A fasting blood sugar will be obtained.
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Fasting for a lab test typically lasts eight hours. Your doctor should give you any special instructions related to your tests, including fasting requirements. Always follow her or his instructions.