What You Need to Know About Fasting for a Blood Test
A blood test could be the difference between life and death. 70% of medical decisions depend on laboratory results, namely blood tests.
A blood test can help your doctor diagnose you with a condition and start a treatment plan. Yet you can’t just walk into a hospital and have your doctor draw blood. Before your appointment, you need to know about fasting for a blood test.
Why is fasting necessary? How long should you fast for a blood test, and can you drink water when fasting for a blood test? What other rules do you need to follow?
Answer these questions and you can get accurate information about your health in no time. Here is your quick guide.
Fasting for a Blood Test Promotes Accuracy
The foods you eat contain nutrients that go into your bloodstream. Carbohydrates, proteins, and fats are present in your blood, and a blood test can pick them up.
The nutrients can also skew parts of your blood chemistry. Carbohydrates can increase your blood sugar levels while fats can increase your cholesterol.
By fasting, you prevent these nutrients from affecting your lab results. It takes time for these nutrients to pass out of your bloodstream, so you need to avoid eating for a set number of hours. Most people need to fast for 10-12 hours before getting their blood drawn.
You can break your fast as soon as your blood has been drawn. You may want to bring a snack with you, but many medical facilities have snacks on site.
But Fasting Isn’t Always Necessary
Some of the most common blood tests require fasting. A basic metabolic panel test measures your blood sugar and organ function rates. Avoiding food will let your doctor get an accurate reading of how your organs are doing.
Fasting blood glucose tests measure your blood sugar levels when you have not eaten carbohydrates. High test results indicate that you may have insulin resistance or type 2 diabetes. In order to get a good result, you need to avoid all foods for 8-10 hours before your test.
You may need to avoid certain foods and drinks for a longer period of time. Gamma-glutamyl transferase tests measure levels of enzymes that indicate liver disease. You must refrain from drinking alcohol for 24 hours.
However, many tests do not require fasting. Hemoglobin level, renal function, and thyroid hormone tests are three common tests that do not require fasting.
You may be exempt from fasting if fasting would make you faint or drop your blood pressure levels to an unhealthy degree. Talk to your doctor if you need to fast and figure out how long you may need to do so.
You May Need to Avoid Other Activities
Achieving more accurate results means more than just avoiding food. Every person is different, and biological factors like genetics can affect results and rules for fasting blood tests. Contact your doctor to see what exactly you need to do.
Chewing gum can speed up your metabolism and digestion, which can affect test results. You also may swallow your gum by mistake. You should avoid chewing gum for a few hours before your test.
Cigarette smoke can leave chemicals in your blood and destroy other substances in your body. At a minimum, you should stop smoking for 24 hours before your test. You may be able to use nicotine patches, though nicotine can skew test results.
You can go out for a walk or do some stretches. But extensive exercise can affect your results, especially if you are getting your blood sugar or cholesterol levels tested. Do not lift weights or go for a run a few hours before your test.
You Can Drink Water Before a Test
Drinking water before a blood test is always a good idea. Water provides fluid for your veins, allowing a doctor to draw blood more easily. It also keeps you from being faint after your blood has been drawn.
You can drink water whenever you want before a test. Try to drink water without any additives, including vitamins and minerals.
Do not add lemon or lime juice to your water, as they contain minerals that will skew your results. You can drink hot or cold water.
Caffeinated beverages act as diuretics, dehydrating you and thinning the fluid in your blood. You should avoid drinking coffee and tea the morning before your test. You should also avoid drinking juice, milk, and soda, as they can also affect your test results.
It’s Okay if You Eat by Accident
Following the rules for a fasting blood test will allow you to receive the most accurate results. But eating a little food won’t skew your results by too much. If you eat something by mistake, you should call your doctor and see if they can interpret the test results.
If they cannot, you can reschedule your fast for another time. Make sure not to eat again before your test. Try eating a full meal the night before your test that contains high levels of protein, which will keep you full for a longer period of time.
Fast for a Test the Right Way
Fasting for a blood test lets doctors get an accurate reading of your blood chemistry. Most tests require fasting, but not all. You should always talk to your doctor before getting a test.
You should drink water to avoid dehydration, but you should avoid all other beverages. You should also avoid exercise and cigarettes. If you eat food by accident, you should give your doctor a call and reschedule your appointment.
Get all the information you need for an accurate blood test. Precision Labs runs blood tests for Midwestern medical facilities. Read our guide to blood testing services today.