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What Should I Eat the Day Before My 3-Hour Glucose Test?

Medically Reviewed on 7/15/2025
Disease and Condition: Diabetes Mellitus

What is an oral glucose tolerance test?

What should I eat the day before my 3 hour glucose test?
Before a glucose test, you may consume about 150 grams or 10 servings of carbohydrates.

An oral glucose tolerance test (OGTT) measures the body's response to glucose from foods. OGTT can identify if you have or are at risk of diabetes. Doctors may use a shorter version of the OGTT to check for diabetes during pregnancy.

OGTT is recommended if you have the following conditions:

A shorter version of the OGTT may be performed between the 24th and 28th week of pregnancy to identify gestational diabetes.

What should I eat before my 3-hour glucose test?

For about three days before the test, you can eat about 150 grams or 10 servings of carbohydrates. These should be taken over the whole day.

One serving of carbohydrate

  • One slice of bread = Half a large bread roll or muffin
  • One-fourth of Lebanese bread
  • One apple = One orange = One small banana
  • Medium mandarin = Two peaches = Three apricots = Three prunes
  • Two Weetabix
  • One-fourth cup muesli = One-third cup Just Right = Half cup bran flakes (most people would have two to three servings of cereal for a meal)
  • Three-fourths cup of cornflakes (most people would have two servings of cornflakes for a meal, that is, a bowlful is about one and a half cups)
  • Two biscuits (milk coffee, shredded wheat, and full-o-fruit)
  • One cup of milk
  • One 200-gram carton of yogurt
  • Half cup cooked pasta (most people would have 1 to 1.5 cups of pasta for a meal, which would be two to three servings)
  • One-third cup cooked rice (most people would have two-thirds to one cup of rice for a meal, which would be two to three servings)
  • One medium potato
  • One small corn cob

You can consume some extra fruit juice or biscuits instead of bread and cereals. Include meat, fish, eggs, cheese, butter, and margarine during these three days.

Do not eat or drink anything after 10 p.m. on the night before the test. Refrain from smoking after 9 p.m. the night before the test.

SLIDESHOW

Diabetes: What Raises and Lowers Your Blood Sugar Level? See Slideshow

How is an oral glucose tolerance test performed?

You will fast for 8 to 10 hours before the test starts.

The test procedure is performed in the following manner:

  1. The nurse collects an initial baseline blood sample.
  2. You will be given a glucose drink with 75 grams of glucose, which should be consumed within five minutes.
  3. Further blood samples are collected every 60 minutes.
  4. Your blood glucose level will be tested one, two, and three hours after drinking the solution.
  5. Once the test ends, you should have something to eat and drink (it is best to take it with you).

Are there side effects of the oral glucose tolerance test?

The oral glucose tolerance test does not cause any serious side effects. Some people may have side effects from sugary drinks or blood tests.

Side effects due to sugary drinks may include:

Side effects of blood tests may include:

  • Excess bleeding
  • Bruising
  • Fainting
  • Infection due to improper handling of vein
  • Issues with finding a vein

Health News

Medically Reviewed on 7/15/2025
References
Image Source: iStock Image

https://www.webmd.com/diabetes/guide/oral-glucose-tolerance-test

https://www.mayoclinic.org/tests-procedures/glucose-tolerance-test/about/pac-20394296

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