Fasting for Blood Work: Tips and Guidelines for a Successful Test


Blood work, or specific blood tests, is valuable for health checkups and diagnostics. They are often one of the initial steps on many paths to treatment for various ailments and conditions. In some cases, fasting helps ensure accurate test results. While it may seem simple, proper preparation for blood work is essential to avoid skewed results that could lead to a misdiagnosis or incorrect treatment; failing to prepare correctly can translate to higher medical costs and additional time suffering from symptoms. 

There are few things more confusing than conflicting information regarding fasting. To help avoid improper preparation and to answer common questions related to fasting for blood work, we will discuss why fasting is necessary for specific blood tests, how to fast effectively, and what to do after the test.

Why Fast Before Blood Work?

Fasting is necessary for several blood tests to get reliable results. These examinations often assess triglycerides, cholesterol, blood sugar levels, and other markers affected by dietary intake.

The amount of these compounds in your bloodstream can change after you eat because your body processes the meal. Fasting gives your body the time required to properly digest and process food, ensuring more reliable test results.


How to Fast for Blood Work

Fasting for blood work is crucial for obtaining accurate results. The fasting period typically ranges from 8 to 12 hours, but your healthcare provider will give you specific instructions based on the test you will be undergoing. Here is the pertinent information you will need about fasting for blood work:

Follow the instructions from your healthcare provider

Always follow your healthcare provider’s instructions, as different tests have different needs.

Plan your fast accordingly

Plan out your fast so that most of it occurs while sleeping. It will be simpler to control hunger and discomfort as a result. This minor consideration may increase your ability to follow fasting protocols. To help, leave a note on your nightstand or a reminder on your phone so that you remember you are fasting upon waking. 

Hydrate with water

While fasting, you can and should continue to drink water unless instructed otherwise. Staying hydrated will help curb hunger, making it easier for the phlebotomist to draw your blood. Studies have found dehydration can affect the accuracy of test results. Dehydration can make undergoing a fast harder. 

Avoid coffee and tea. Even though these beverages are low in calories, they may still interfere with your blood test results. Stick to drinking water during the fasting period. 


Skip calorie-free gum and candies

Contrary to popular belief, zero or low-calorie chewing gum or candies is ill-advised when fasting is required. The reason is that chewing gum and consuming hard candies can stimulate the production of stomach acid, which can affect your blood test results.

Continue taking medications as prescribed

Unless your healthcare provider advises otherwise, continue taking your prescribed medications as usual. However, be sure to inform your doctor of each medicine you take. 

Inform your healthcare provider about any supplements

Some vitamins and supplements can interfere with blood tests. Always inform your healthcare provider about any supplements you are taking, including those classified as natural supplements. 

Don’t smoke

While cigarette smoking would never be advantageous, that is especially true when fasting because smoking cigarettes affects oxidative stress and hematological indexes during blood testing.

Stay busy

Your greatest battle will likely be on the mental side of the fasting equation. To help offset this instinctual struggle, keep your mind occupied by engaging in activities or hobbies that help you avoid thinking about food.

Be mindful of overeating before your fast

While it may be tempting, eating a large meal right before your fast may lead to indigestion or other issues during the fasting period. Instead, choose a balanced meal with a healthy mix of protein, complex carbohydrates, and healthy fats.


What to Do After the Blood Test

Once you have completed your blood test, taking care of yourself and following some guidelines is essential to ensure a smooth recovery.

Break your fast slowly

After a fast, your body may be more sensitive to some foods. Start slowly by eating things that are simple to digest, such as fruits, yogurt, or a smoothie. When your body adjusts, gradually introduce more solid foods.


Keep drinking water to replace any fluids lost during the blood draw and the fasting interval. Doing this will ensure a faster recovery and return to your routine. 

strawberry smoothie for breaking up fasting


Feeling worn down and tired is normal after a blood test, especially one requiring fasting. Give your body time to recover by resting and taking it easy for a few hours.

Monitor any side effects

After a blood test, some people may experience minor side effects like dizziness or bruises. Look for any symptoms, and contact your doctor about any concerns or questions.

Resume your regular diet

You can resume your regular eating schedule when you’ve broken your fast and feel ready. Take advantage of this chance to review your diet and, if necessary, switch to a better diet.

Follow up on your results

Your blood test results will be given to you by your doctor, typically within a few days. Follow up and discuss any necessary actions or modifications to your healthcare strategy in light of the findings.

Final Thoughts

Getting accurate test results requires fasting before blood work. Make sure that the blood test results from your fast are as precise as possible by adhering to the fasting instructions and advice offered in this article. Always remember that the short-term difficulty of fasting is a modest price to pay for the long-term advantages of knowing about and looking after your health.

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