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Understanding Portion Size

By in Nutrition

The portion, or the amount of food you eat, affects blood glucose levels.  For foods that contain carbohydrates, the larger the portion size, the more carbohydrates it will have.  For foods that are a combination of fat and protein, large portions can affect your glucose over a long period of time. Knowing the actual portion size of the foods you eat, can help in determining correct carbohydrate counts and insulin doses. The best way to know how food much you are eating is to measure it.

Tips for Measuring Food

  • Use measuring spoons and cups for foods measured in teaspoons, tablespoons and cups. Use a food scale to weigh food that is listed in grams, ounces or pounds.
  • Use smaller plates, bowls and cups so you are not tempted to always fill the larger ones.
  • Remember that some vegetables and all fruits have carbohydrates that need to be counted. A large banana will have more carbohydrates than a medium one.

Portion Size Tips for Eating Out

It can be difficult to know the portion sizes of food when eating out.  Here are a few tips for estimating correct sizes.  The measurements are using an average-size adult hand.  Before using the guide, compare your hand to a 1 cup measurement and adjust as needed.


  • 3 oz. (about the size of the palm of your hand) – typical portion size of a serving of meat or poultry
  • 1 oz. (about the size of your thumb) – typical size of a serving of cheese
  • 1 cup (about the size of a fist) – typical serving size of vegetables



Updated 2/17/19

This document is not intended to take the place of the care and attention of your personal physician or other professional medical services. Our aim is to promote active participation in your care and treatment by providing information and education. Questions about individual health concerns or specific treatment options should be discussed with your physician.