why do i need to fast before blood test?
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If your doctor asks you to fast before a blood test, it's to ensure the results of the blood test are as accurate as possible. That's why a fasting blood test usually requires fasting for 8-12 hours before your blood is taken.
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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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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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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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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. That way, most of your fasting time will be overnight.
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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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If you are having a vitamin B blood test, you may need to fast (not eat or drink) for several hours before the test. You don't need any special preparations for a urine test.
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a fasting blood glucose test (used to test for diabetes) – you fast for 8 to 10 hours before the test.
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Common fasting blood tests Examples of blood tests that require you to fast include: a fasting blood glucose test (used to test for diabetes) – you fast for 8 to 10 hours before the test. an iron blood test (used to diagnose conditions such as iron deficiency anaemia) – you fast for 12 hours before the test.
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The most common types of tests that require fasting include: Glucose tests, which measure blood sugar. One type of glucose test is called a glucose tolerance test. For this test you will need to fast for 8 hours before test.
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Fasting means that you abstain from all food and fluids other than water for a period of 8-14 hours prior to your test. Alcohol should not be consumed for 72 hours (3 days) prior to the test. You should avoid smoking during the fasting period. Do not fast for more than 14 hours prior to your testing.
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It's fine to drink water before a blood test, unless you're instructed otherwise by your doctor. This is different from some surgical procedures, which may require you to have a totally empty stomach. Tap or bottled water are both OK, but leave the squeeze of lemon for another time.
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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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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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Getting your cholesterol levels tested is an important part of keeping your heart and blood vessels healthy. In general, fasting before your test isn't required. But your doctor may recommend fasting if you're already taking a cholesterol medication. Be sure to ask your doctor before your test whether you need to fast.
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Diabetes Fasting and Insulin. Your doctor has suggested a test that requires you to fast before the test. This means you will not eat food or drink liquids for a period of time before the test. If you have diabetes and take Insulin, this Test Facts will help you fast and control your blood sugar (glucose) levels.
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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. That could cause your appointment to be rescheduled. If at any point you're unsure if fasting is required, contact your doctor.