Blood Tests That Require Fasting

At some point in your life, you will be required to go for a blood test. It could be for a general check-up or screening for some diagnosis. Whatever it may be, blood tests are essential for giving insights into your health. For instance, a private GP can determine a person’s iron level, whether it is within the normal range or deficient. It is the same with other nutrients.

Fasting is abstaining from food and other beverages between 8 and 12 hours before taking a blood test. It is a standard procedure for patients before they undergo a blood draw. However, blood tests are different. You need to know which test requires fasting and whether you can take some liquid during this fasting period. With this, you can understand what you need to do to prepare for the test so that your results can be accurate.

Why should I fast before taking some blood tests?

Blood tests help doctors to understand the state of your health and its baseline. But when you consume food or drinks before the test, they alter your body’s typical nutrient level. For example, if you are hypoglycaemic, taking food before having the blood test can increase your sugar level and make it difficult for the doctor to detect the abnormalities and correctly diagnose the condition. This can hinder the doctor from knowing whether the food you ate influenced the result or if you are truly hypoglycaemic.

What if I don’t fast before the test?

If you did not fast before your blood test, you need to tell your healthcare provider immediately. Depending on the physician and the test, you may be asked to go for an alternative test available, or they reschedule your appointment. It is better to reschedule your appointment than undergo the test and have an incorrect result and diagnosis. Having a wrong diagnosis will alter your treatment plan.

Blood tests that require fasting

The following are the blood tests that you should fast for;

  • Blood glucose test: This blood test is done to measure your blood sugar level. You need to fast for about 8 to 10 hours.
  • Gamma Glutamyl Transferase (GGT): This test gives an insight into the GGT enzyme and your liver health. The fasting time is 8 to 10 hours.
  • Glucose Tolerance Test: This blood test is carried out to evaluate your blood sugar levels. It needs a fasting time of 8 to 12 hours.
  • Liver function test: This blood test provides all the information about the enzymes and liver nutrients. It requires a fasting time of 8 to 12 hours.
  • Renal function test: This blood test evaluates your kidney functioning and your body’s ability to filter waste. It requires a fasting time of 8 to 12 hours.
  • Vitamin B12 test: This blood test will tell whether or not you are deficient in vitamin B12 and its impact on your system. The fasting time is from 8 to 12 hrs.
  • Lactose Tolerance Test: This blood test determines how much you can tolerate dairy products. The fasting time is from 8 to 12 hours

Though you may need to fast for 8 to 10 hours before a test, some tests will require 12 hours long of fasting. They include;

  • Lipid profile test: This test is used to measure the amount of triglycerides and cholesterol in your blood. It requires of fasting time of 12 hours.
  • Thyroid function test: This blood test measures the number of thyroid hormones you have, which are highly impacted by your diet. It requires a fasting time of 12 hours.
  • Iron test: This blood test is used to evaluate your iron levels, and you will be diagnosed if your doctor suspects anaemia. It requires a fasting time of 12 hours.

Is it better if I fast for more than 12 hours before a test?

You should not fast longer than 12 hours before the test. While fasting is essential to make your blood test result valid and reliable, fasting for too long can cause dehydration and other side effects. When undergoing a fast, remember that sleep is also regarded as fasting. For instance, if your appointment is by 8 a.m, sleeping from 9 p.m to 7 a.m makes up to 10 hours of fasting, as long as you do not eat anything in the morning before going for the appointment.

Can I take liquids while fasting?

Fasting goes beyond avoiding food. So, when fasting for your blood test, you should not drink any beverage besides water. Although some patients say that beverages are different from food, they can still influence your test results and their credibility. For instance, if you drink orange juice, it can influence your vitamin C level during a test, producing false data. So it is imperative to avoid consuming beverages like orange juices because they can make it difficult to differentiate between the normal range of your enzymes and those impacted by the vitamins, sugar, and minerals contained in the beverage. Generally, you should avoid taking tea, soda, coffee, alcohol, and juices before a blood test.

Remember that it is essential for you to stay hydrated during fasting to make blood draws easier.

In addition to beverages, you should also avoid;

  • Chewing gum
  • Smoking
  • Taking multivitamins and supplements
  • Strenuous exercise
  • Some medications. In using drugs, ensure you tell your doctor about the current medicines you are on. It may be okay to take some medicines during fastings, but you need to be sure if the one you have must be avoided, especially if it must be taken with food.

Do you want to have a private blood test?

Would you like to have a same day private blood tests London for a general check-up or diagnosis? Book a private GP appointment today at our site.

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