July 8, 2022
When you’re tired, you sleep. When you’re thirsty, you drink. And when you’re hungry, you eat. Unless, that is, your doctor recommends fasting before a blood test. In which case, what should you do?
We’re so accustomed to responding to hunger by immediately eating food that the simple request to fast for a period of time can send us spiraling. How long should I fast? Is a little snack okay? Can I still have my morning cup of coffee? What if I take prescription medicine?
With so many questions, we wanted to provide some facts about fasting before blood tests, why it’s important, how long you should fast, and some explanations about why eating before a blood test can impact results.
Let’s dive in.
It’s recommended that you fast anywhere between 8 to 12 hours before a blood test. Certain blood tests require longer or shorter fasting times, in which case, your doctor will inform you about the appropriate amount of time. Fortunately, most blood tests are scheduled for early in the morning, so the majority of fasting will take place while you sleep.
Blood tests help doctors understand how your body is functioning and check for certain health problems. To provide the most accurate picture of your overall health, it’s important to establish a baseline measurement of your results. Because everything you eat and drink contains nutrients that can impact different measurements, abstaining from food and drink is critically important to receiving accurate results.
For example, if you eat an entire sleeve of Oreo cookies before a blood glucose test, your blood sugar levels will be much higher than if you hadn’t eaten anything at all. This could alert your doctor to medical conditions that aren’t actually present by skewing the test results far outside their normal range.
Not every blood test requires you to fast, and your doctor will likely notify you if fasting is not required. Here are a few blood tests that you should fast for:
Yes! You’re allowed to drink water while fasting before a blood test. In fact, drinking plenty of water before a blood test is encouraged as it can help keep you hydrated. Dehydration can impact the results of certain blood tests, so ensuring you have plenty of water in your system will improve the accuracy of your blood test.
No, even black coffee can interfere with the results of your blood test. Coffee contains caffeine and is also a diuretic, which means it removes water from your body. Save that cup of Joe for after the blood test.
Not really. Juice, soda, and alcohol all contain high-levels of sugar and will interfere with your test results.
Tea is similar to coffee in that it contains caffeine and is a diuretic and removes water from your body. It’s best to avoid drinking all non-water beverages before taking a blood test.
Besides not eating or drinking any non-water beverages, you should also avoid exercising, smoking, or chewing gum. These can activate your digestive system and affect results.
It’s okay to continue taking your prescription drugs, unless your doctor asks you to skip them. However, you should ask your doctor before taking any over-the-counter medication as it may skew results.
Once the blood draw is complete and the phlebotomist collects all the samples they need, you’re free to eat and drink whatever you want.
Fasting before a blood test can be uncomfortable, but it’s important to follow these guidelines to ensure your test results provide an accurate picture of your health. Fortunately, if you’d like to quickly break your fast as soon as the blood draw is complete, Getlabs can help.
Getlabs provides the perfect solution for patients who prefer to take blood tests in the comfort of their homes. With over 5,000 different lab tests available, you can book a nearby phlebotomist for many of the tests your doctor may recommend.
If you want to learn more about Getlabs, visit www.getlabs.com/faq to learn more.
This page is provided for educational and informational purposes only and does not constitute the provision of medical advice or professional services. The information provided should not be used for diagnosing or treating a health problem or disease, and those seeking personal medical advice regarding any of the tests and conditions referenced above are advised to consult with a licensed clinician. Always seek the advice of your qualified health provider regarding a medical condition and do not disregard professional medical advice or delay in seeking it because of any information on this page. If you think you may have a medical emergency, immediately call 911 or go to the nearest urgent care center or hospital.
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