Fasting for Blood Work: The Do’s and Dont’s for Accurate Testing
When your physician requests that you fast before getting blood work done, it means that they need to refrain from eating (and sometimes drinking) for a specified amount of time. For many, fasting for blood can be an uncomfortable headache. But some blood tests require fasting in order to obtain more accurate results.
In this article, we’ll explore why blood fasting is necessary and what you can do to get through the process as painlessly as possible.
Why Is Fasting Required for Some Blood Work?
When blood work is needed, your physician, nurse, or a lab associate will let you know if fasting is required. While fasting is not always required with blood testing, sometimes the intake of food and drink can affect results depending on what’s being tested for. It’s crucial that fasting requests are followed for the most accurate test results to be obtained. Here are some common examples of blood tests that commonly require fasting:
- Cholesterol Level Testing – When you’re scheduled for a cholesterol test, your doctor will be assessing your resting levels of “good” HDL cholesterol and “bad” LDL cholesterol. Because cholesterol levels can be temporarily impacted by food and drink being consumed, you will most likely be asked to fast before the test for nine to twelve hours.
- Blood Glucose Testing – Fasting blood glucose tests check the levels of sugar in an individual’s blood. Glucose testing can be necessary for determining that healthy blood sugar levels are present and what the diabetic status of a patient is. Because the consumption of many foods can temporarily impact internal sugar levels, you may be asked to fast for eight to ten hours before testing.
- Iron Level Testing – When you have an iron level test scheduled, your physician will be checking for conditions, such as blood anemia, that can lead to low levels of the vital mineral iron. Because certain foods contain iron, you may be asked to refrain from eating the morning prior to your test.
- Vitamin B12 Level Testing – Vitamin B12 is an important component your body needs to support nerve and blood cell health. Certain foods can affect blood glucose levels; therefore, you may be asked to fast for six to eight hours prior to testing.
- Renal Function Testing – Your kidneys handle the task of removing fluid and waste from your body. You may be asked to fast for eight to twelve hours prior to a renal function blood panel test so that kidney function isn’t impacted.
- Comprehensive Metabolic Testing – Comprehensive metabolic tests will test for a combination of electrolyte balances, kidney function, and blood sugar levels. Your physician may ask you to fast for ten to twelve hours prior to blood testing for the most accurate results.
How to Prepare for Fasting Blood Work
If you have an upcoming fasting blood test, it’s vital to prepare accordingly. Preparation for fasting blood work will not only help ensure the accuracy of your testing, but it can also help make the process a little easier to handle. Here are some tips to help with blood work preparation:
- Time Yourself Correctly – Fasting correctly primarily comes down to timing yourself. Once you have been provided with your testing time and fasting requirements, be sure to time your eating around those requirements. If you have a test at 8 a.m., for instance, and your physician has instructed you to fast for 12 hours, it’s important that you don’t have anything to eat past 8 p.m. To help ensure your hunger levels don’t get to an extreme degree, try having a small snack shortly before 8 p.m.
- Drink Your Water – Hydration levels can directly impact blood work results. Be sure to consume plenty of water and stay hydrated before your blood testing.
- Coordinate with Your Physician – If you have any questions or concerns regarding fasting, it is important that you discuss them with your physician prior to your fasting time beginning. One instance in which it is important to coordinate with your physician is when you’re pregnant. While it is generally safe to fast while pregnant, it’s important that you do so safely and under a physician’s guidance.
- Continue Taking Your Medication – Unless otherwise directed by your physician, it’s crucial that you continue taking any regular medications throughout your fasting schedule. Due to some medications having requirements of being taken with food, it’s essential that you speak with your physician to determine the best way to approach this.
What Not to Do When Preparing for Fasting Blood Work
Just as it’s crucial to follow specific steps prior to your blood work appointment, there are also things that you should try to avoid. Below we’ll review some standard actions to avoid during blood test fasting:
- Don’t Smoke – Smoking should always be avoided, but particularly so when you have a blood test scheduled. Smoking can impact your bodily functions in profound ways; therefore, it should be avoided to ensure accurate testing.
- Avoid Alcohol – Because alcohol contents can directly affect your blood sugar levels, fat levels, blood pressure, and more, it should be avoided during your fasting period.
- Don’t Chew Gum – It has been shown that the act of chewing gum can directly impact your digestive system by increasing gastric juice production, which can stimulate bowel movements. Gum with sugar as an ingredient should also be avoided because it can affect fasting blood glucose levels.
- Restrict Exercise – While exercise is generally good for you, it can adversely affect blood testing if conducted during your fasting period. Exercising can impact your digestive system and, in fact, speed up your body’s digestive process. During your scheduled fasting time, you should avoid exercising unless otherwise directed by your physician.
- Don’t Drink Coffee – Coffee is another item that can impact your body’s digestive process. To prevent your blood work from being adversely affected by coffee consumption, you should avoid consuming this beverage until after your fasting and blood testing periods are over.