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Fasting for a Blood Test: All You Need To Know

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What is Fasting for a Blood Test | Blood Tests Requiring Fasting | How Long To Fast Before A Blood Test | Can you Drink Water | Can you Drink Coffee | Can you Take Medicine

Fasting for blood test results – an official guide to help you before you go. Your doctor must have asked you to observe a fast before you undergo specific blood tests. Fasting for a blood test is essential to obtaining accurate blood work results in certain types of blood tests. 

In this post, we will discuss all you need to know about fasting for blood work, including what it is, how long you need to fast, some of the blood tests that require a fast, and things you need to do before your scheduled blood test.

What is Fasting for a Blood Test or Blood work?

Intermittent fasting is when you deliberately deprive your body of food for a specific duration for physical, mental, psychological, or spiritual reasons. However, blood work fasting is when your physician instructs you to deprive yourself of certain foods or food in general for a specified length of time before a scheduled blood test. 

The nutrients in food, including carbohydrates, fats, minerals, proteins, and vitamins, adversely interfere with the blood test leading to an inaccurate result on your test. To avoid such issues, your doctor recommends fasting for a blood test. It must be stated that not all blood tests require you to fast. 

Blood Tests Requiring Fasting for Blood Work

Blood Tests Requiring Fasting for Blood Work

The type of blood tests that most doctors recommend for fasting include:

1. Blood Glucose Test

This blood test helps to determine your blood sugar level. A blood glucose test is done to diagnose prediabetes or Type 1 diabetes. It is, therefore, a useful preventive measure to indicate your blood sugar level while also helping guide you on what diet you should embrace in the future. Your doctor would normally require that you fast for a minimum of 8 hours before the test.

2. Comprehensive Metabolic Panel Blood Test

This test is often recommended during a regular physical examination. The blood test determines your fluid balance, electrolyte, blood sugar, and liver and kidney functions. This test requires you to fast up to 12 hours before your scheduled blood work.

3. Gamma-Glutamyl Transferase or GGT Blood Work

This test reveals the GGT enzyme level in your body. If you have a high GGT, it could be a result of alcohol abuse, an indication of bile duct issues, or even liver disease. A fast for this type of test is essential, and your doctor may require that you fast for 8 hours before your scheduled blood work.

4. Lipid Profile Blood Test

This type of blood test determines your cholesterol level and the triglycerides (blood fats) in your body. If you have high levels of cholesterol or blood fats, you will be at risk of stroke or cardiovascular disease. The fasting time for this type of blood test is usually between 9 to 12 hours.

5. Iron Blood Test

This blood work checks for iron levels. Iron is a vital mineral in your blood and crucial to hemoglobin production in red blood cells. Hemoglobin is responsible for conveying oxygen directly from your lungs to every other part of your body, including your brain. Iron deficiency leads to fatigue due to a shortage of red blood cells carrying oxygen to all parts of your body system. You will need to fast for 12 hours before undergoing this blood test.

6. Vitamin B12 Blood Test

With this blood work, your doctor would want to know the level of vitamins in your blood. This test is used to diagnose blood conditions like anemia. Typical fasting for this blood test will be between 6 and 8 hours.

How Long To Fast – Fasting for blood tests

One question that often asked is – how long fasting blood work is required. There is no easy answer to this question because there are so many types of tests, and each one may need an X-amount of fasting time that your doctor would determine. 

Before blood work, your doctor may roughly recommend overnight fasting for a blood test. 

Most blood tests are scheduled in the morning, and since you sleep for up to 8 hours throughout the night, right up to the early hours of the morning, you should be all-clear for blood work by the next morning. But if you are unsure how long to fast before a blood test, ask your doctor. 


Can you Drink Water When Fasting for Blood Work?

You are typically allowed to drink water when fasting for a blood test, except if you are instructed to the contrary by your physician. If you are permitted to drink water, you should only drink bottled or tap water. Do not drink flavored water or add lemon to your drinking water.

Avoid carbonated drinks, club soda, seltzer, or tea before your scheduled blood work. Drinking water before your blood test will keep you hydrated and help make it easy for a nurse to find a vein from which to draw blood during the test.

Can you Drink Coffee When Fasting for Blood Work?

No. The soluble plant matter and caffeine contained in coffee are known to disrupt the results of blood work adversely. In addition, coffee is a diuretic and, therefore, will increase your urination rate, leading to dehydration.

The importance of this to blood work is that dehydration makes it difficult for the nurse attending to you during your blood work to locate a vein when trying to draw blood. The blood test can be frustrating, painful, and stressful if a vein is hard to find. So in fasting for blood work coffee should be avoided at all costs, even if drinking the beverage is part of your daily routine. 

Can I Take Medicine When Fasting for Blood Tests?

There is no straightforward answer to this question. However, on most occasions, it may be alright for you to take prescription medicines while fasting for blood work.

But also, if your medication is supposed to be taken along with food, your doctor may recommend that you do not take medicine before your scheduled blood test. It would be best to communicate with your doctor, as every case is different. So if your doctor gives you the go-ahead to take medication during your fast, then, by all means, do as they advise.

Other Activities to Avoid Before Fasting for Blood tests

If you are a cigarette smoker, you should inform your doctor during your routine checkup. Ideally, you should not smoke cigarettes at all, as they are bad for your health, but in this case, you should avoid smoking at least 8 hours before your blood test. You should also avoid exercising as a workout session will make you sweat, which could lead to dehydration and make finding your vein hard.

Chewing gum should equally be avoided as well. If you should eat, drink a beverage or take medication while you should be fasting, make sure to inform your doctor. Do not hide anything from your doctor, as they would be in the best position to advise you on what you should do in such situations. 

In Conclusion

Fasting for blood tests, what should you do? The question of how many hours of blood work fasting is simple.

Depending on the type of blood test you are scheduled to undergo, you should fast for 8 to 12 hours before your blood work. Fasting for blood work should be per your doctor’s recommendation, and you should inform them if you should ever break the fast for whatever reason. 

Drinking water is often allowed, but you should never add flavorings to it. If you are on prescription meds, you will need to ask your doctor if you can take them while you fast. Smoking is bad for your health, so avoid smoking cigarettes, especially before your blood work, as smoking can lead to dehydration and make drawing blood difficult.

Also need help fasting? Check out these Top 6 Fasting Mobile Apps we recommend to help you on your journey.

I recommend starting here to learn more about these types of fasting which are the MOST popular, starting with 16/8 Fasting, click on these guides below to learn more:
16/8 Fasting Guide, 14/10 Fasting Guide18/6 Fasting GuideOne Meal a Day Guide.

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