Should I Eat Before A Blood Test


Should I Eat Before A Blood Test? Many patients wonder if they should eat before a blood test. This can be a difficult question to address with certainty. There are factors to consider, like what kind of blood test you’re having and your health status. I’ll cover some of the most common concerns in just a moment.

Depending on your circumstances, you may be asked to fast before your blood test – that is, to have nothing to eat or drink other than water for a period of time prior to the test. Failure to follow any instructions regarding food and drink intake can alter the outcome of your blood test.

Should I Eat Before A Blood Test

An individual should refrain from eating or drinking anything than water before having certain blood tests, which is known as fasting. Which blood tests, though, need patients to fast, and how can they do so safely?

Before a blood test, a person is not always required to fast. Usually, only a brief period of fasting is necessary when a blood test is required.

Even yet, it could seem intimidating to go without food or liquids for even a short while. It can be less stressful if you know when and how to fast before a blood test.

This page examines the various blood tests that necessitate fasting, why it is essential, and safe fasting techniques.

How long to fast before blood test?

Whether someone needs to fast or not before a blood test depends on the type of blood test they need to undergo. Some blood tests require fasting to provide accurate results, while others do not.

The types of blood tests that require fasting are:

Fasting blood glucose test

Diagnosing diabetes can be aided with a fasting blood glucose test.

Diabetes is a disorder that can cause the blood sugar to rise too high. A fasting blood glucose test examines blood sugar levels to determine their wellness.

It’s crucial that someone has gone 8–10 hours without eating or drinking anything than water before having a fasting blood glucose test. Usually, a person takes the test early in the morning after fasting overnight.

Fasting makes it easier to get an accurate reading of fasting blood sugar levels during the blood test. The outcomes support a doctor’s diagnosis or exclusion of diabetes.

Blood cholesterol tests

Cholesterol is a fatty substance in the blood. High cholesterol can lead to an increased risk of certain health conditions.

Blood cholesterol tests, also known as lipid profiles, assess the quantities of fats in the blood. The different fats tested for include:

  • high-density lipoprotein cholesterol, also known as “good” cholesterol
  • low-density lipoprotein cholesterol, also known as “bad” cholesterol
  • triglycerides

If a person has recently eaten, the level of these fats will rise. People are advised to abstain from food for 9 to 12 hours prior to the test in order to provide an accurate profile of the levels of these fats in the blood.

According to several studies, not all cholesterol and triglyceride testing require fasting. Nonetheless, those who are undergoing these tests should abstain from alcohol for 24 hours prior to the examination. It is advisable for people to see a doctor before determining if these new regulations apply to them.

Gamma-glutamyl transferase test

The GGT test aids in the identification of liver disease. The liver has an enzyme called GGT that contributes to its efficiency.

It may be necessary to refrain from eating, drinking, and using any prescription medications for eight hours before to the test.

Iron blood test

The amount of the mineral iron in the blood is determined via an iron blood test. This examination aids in the diagnosis of diseases like anemia that are brought on by low blood iron levels.

Certain foods include iron, which the body absorbs swiftly into the bloodstream. As a result, if someone eats before getting an iron blood test, the findings might be overstated.

A person should fast from midnight the night before the test until the results are in order to ensure reliable results.

Other blood tests that require fasting

People may be asked to fast for:

  • Blood glucose test: This tests the sugar in a person’s blood and can help confirm or rule out diabetes.
  • Liver function test: This looks at how well a person’s liver is working.
  • Serum electrolyte and kidney function tests: These tests look at the function of the kidney to assess for chronic kidney disease.
  • Vitamin B12 test: This tests for the levels of vitamin B12 in a person’s blood. Typically, people are asked to fast for 12 hours before the test. They must also let the doctor know whether they take any medications, as some can interfere with the test.

Why fasting is required

Alcohol consumption causes the food and liquid consumed to be digested in the stomach and absorbed into the bloodstream. This may have an impact on how much cholesterol or blood glucose are present in the blood.

The following disorders, among others, require a precise diagnosis of these chemicals’ levels:

  • diabetes
  • anemia
  • high cholesterol
  • liver disease

For correct diagnosis of these conditions, it is important that a person fasts. Eating or drinking before the test may raise the levels of a particular substance in the blood, leading to inaccurate results. Incorrect results could in turn lead to an incorrect diagnosis.

Foods to Avoid Before Having a Blood Test

Man having blood collecting in hospital

Blood tests are frequently used to determine the origin of symptoms, identify or track disease progression, or assess disease risk. The majority of blood tests do not require much preparation in advance since the bulk of the components analyzed are not considerably affected by recent dietary intake. However, some blood tests call for you to fast for up to 12 hours before to the test, consuming just water.

Lipid Panel

A 12-hour fast is necessary for the standard lipid panel, which means only water can be taken in the 12 hours before blood is drawn. This lipid test, also known as a cholesterol panel, measures the blood’s total cholesterol, triglyceride, and LDL and HDL cholesterol levels. These two types of cholesterol are usually referred to as the “good” and “bad” cholesterol. The only aspect of the lipid test that is affected by recent dietary intake is the triglyceride, or fat, level in the blood, therefore a growing trend is to conduct cholesterol testing without fasting.

Blood Glucose

A fasting blood glucose test, which is used to check for the existence of prediabetes and diabetes, must be avoided for at least 8 hours before to the test. Prior to an oral glucose tolerance test, which is done in pregnancy to check for the existence of gestational diabetes, fasting is also necessary. Although it is possible to detect blood glucose without fasting, the fasting test is more frequently employed for diagnostic purposes.

Other Tests

After eating, blood levels of vitamins, minerals, electrolytes, and other nutrients may momentarily rise. Even caffeine and alcohol can change a number of blood component levels. Despite yet, for proper results, most lab tests don’t require fasting. Nonetheless, your doctor might advise that you abstain from eating particular foods or nutritional supplements before undergoing particular tests.

What to eat before the glucose test

When you eat, your body breaks down carbs into glucose, which is your body’s main source of energy. During pregnancy, two types of tests check your blood glucose (sugar) levels to detect and diagnose gestational diabetes. Each requires a different eating strategy.

Glucose screening

Your doctor will perform a glucose screening, often in the morning, between weeks 24 and 28 of each pregnancy (or maybe earlier if you have a higher risk of gestational diabetes). You will consume a sugary beverage for this test, commonly referred to as the two-step test or the one-hour glucose test, and then have blood collected an hour later to measure your blood glucose levels.

Don’t make the error of skipping breakfast even though you might believe that not eating at all before your test will boost your chances of passing. Your blood sugar levels might even become out of whack as a result. Instead, the evening before and the morning of your glucose screening, you should consume a meal that is balanced in healthy carbs and protein.

“Good” or “complex” carbohydrates are those that are richer in fiber and take longer for your body to breakdown. You won’t feel blood sugar spikes because of how gently they reach your bloodstream. Foods with complex carbohydrates include:

  • Whole grains, like whole-wheat bread and oatmeal
  • Vegetables, including non-starchy veggies like tomatoes, cucumbers, broccoli, leafy greens and green beans
  • Fresh fruit, such as berries, apples and watermelon
  • Legumes, such as chickpeas, black beans, kidney beans and lentils

For long-lasting energy, balance your meal with protein-filled foods such as dairy, nuts, fish or lean meat like poultry.

Examples of healthy breakfasts during pregnancy that will help you pass the glucose test include: 

  • Whole wheat toast topped with natural peanut butter or mashed avocado
  • Plain Greek yogurt with blueberries 
  • Oatmeal made with low-fat milk and topped with fresh berries
  • Broccoli and cheddar cheese omelet 
  • Tofu scramble with spinach and Swiss cheese
  • Whole wheat burrito filled with scrambled eggs, beans and tomatoes

A smart tip is to keep an eye on your diet before to your scheduled doctor’s appointments. That’s because you’ll probably have to urinate into a cup each time you see your doctor so your medical team can examine the sugar levels in your urine, which could indicate that you have gestational diabetes. Similar to the glucose screening, it is possible to receive a positive result even though you do not have gestational diabetes if you have recently consumed a sugary meal.

Can I continue taking medicine during a fast?

Ask your health care provider. Most of the time it’s OK to take your usual medicines, but you may need to avoid certain medicines, especially if they need to be taken with food.

What if I make a mistake and have something to eat or drink besides water during my fast?

Tell your health care provider before your test. He or she can reschedule the test for another time when you are able to complete your fast.

When can I eat and drink normally again?

As soon as your test is over. You may want to bring a snack with you, so you can eat right away.

Is there anything else I need to know about fasting before a blood test?

Be sure to talk to your health care provider if you have any questions or concerns about fasting.

You should talk to your provider before taking any lab test. Most tests don’t require fasting or other special preparations. For others, you may need to avoid certain foods, medicines, or activities. Taking the right steps before testing helps ensure your results will be accurate.

Glucose tolerance test

Your body may not be making enough insulin to digest the excess glucose in your system during pregnancy if your blood sugar levels on the glucose screening are too high. You might have to return for a glucose tolerance examination (sometimes called the one-step test or three-hour glucose test).

You must fast prior to having your blood collected for this test. Following the consumption of a sugary beverage, you will have three further blood draws at one, two, and three hours.

You must fast for eight to 14 hours prior to your appointment in order to prepare for the glucose tolerance test.

How to pass the glucose screening

For the best results, try to: 

Eat breakfast 

Before the glucose screening, eat a meal that includes both complex carbohydrates and protein. (Remember, if you’re doing the glucose tolerance test, you’ll need to fast for eight or so hours beforehand. Not sure which test you’re taking? Confirm with your doctor.)

Avoid sugars and refined carbs

Avoid eating simple carbs, such as refined grains, or high-sugar items the morning of your glucose test. These foods are quickly broken down by the body, which causes a surge in blood sugar levels. That entails avoiding things like:

  • Orange juice and other fruit juices
  • Sugary granola 
  • Refined cereal 
  • Sugary toppings like jam or syrup
  • Pancakes
  • Doughnuts
  • White bread 
  • Many other sweetened baked goods made with refined white flour, such as banana bread, croissants or muffins

Take a walk

If you can, try to squeeze in a 10- to 15-minute walk after your meal, which can help get your blood sugar levels in check.

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