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Can I eat and drink before a blood test?

Posted by Be Well

Can I eat and drink before a blood test?
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Blood tests are carried out for a number of reasons. For example, to diagnose or rule out certain conditions, to monitor an existing condition, or simply to find out what your blood group is before you have a transfusion.

In most cases, you will be able to eat and drink as normal before having a blood test. However, there are times when you will not be able to eat before a blood test, and you may also be asked not to drink certain liquids, such as tea, coffee, alcohol and fruit juice. This is because eating or drinking certain foods and liquids may affect the accuracy of certain types of blood test. The healthcare professional who is treating you will tell you if there is anything that you need to do in preparation. You should ask them if you have any concerns.

Tests for autoimmune diseases

Sometimes blood is tested to check for conditions affecting the immune system, such as HIV, hepatitis A or B, or cancer. For this test, you may be told not to eat, or to avoid certain foods before the test. However, unless you are told otherwise, it's a good idea to have a snack before the test to stop yourself feeling faint.

Blood cholesterol level

A blood test is often used to check the amount and type of cholesterol in your body. Cholesterol is a fatty substance that builds up in the artery walls and can lead to serious health problems, such as heart disease. There are two types of cholesterol test and, depending on which type you have, you may be asked to fast beforehand.

A test known as the fasting lipoprotein profile may be used to check how much low density lipoprotein (LDL) or 'bad cholesterol' is contained in your blood. Before having this test, you will be asked not to eat for up to 14 hours so that your body has enough time to digest the food in your digestive system, and to clear any fatty particles from your blood.

It is also possible to have a cholesterol test without fasting, but this test can only be used to measure the total amount of cholesterol and the high density lipoprotein (HDL) or 'good cholesterol' in your blood.

Blood glucose test

There are a number of different blood tests that are used to measure blood glucose levels. They are often used to check for diabetes, or to find out how well organs such as the pancreas and liver are processing glucose.

If you are having this test for the first time, you may be asked to continue eating as normal. However, if the results from the test are abnormal, you may need to have a second test, when you will be asked not to eat beforehand. This second test is to check whether your original abnormal blood glucose test result was caused by the food you ate.

Iron test

Blood tests are sometimes used to measure iron levels in the blood, which can help to diagnose conditions such as anemia. Iron tests are usually taken in the morning, before you have had anything to eat. You should also avoid taking iron pills or tablets for 24 hours before the test. This is because iron is absorbed very quickly from food or pills, and can make your blood iron levels higher than normal.

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NOTICE: The information provided on this site is not a substitute for professional medical advice, diagnosis, or treatment. Never delay or disregard seeking professional medical advice from your physician or other qualified health provider because of something you have read on Wellsphere. If you have a medical emergency, call your doctor or 911 immediately.
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