The Glycaemic Index

This leaflet explains what glycaemic index is.


The rate at which carbohydrate impacts on blood glucose depends chiefly on the amount (Carbohydrate Load) and to a lesser extent, the type of carbohydrate (Glycaemic Index).

The Glycaemic Index (GI) is a scale from 1 to 100 that is used to measure how quickly foods that contain carbohydrate raise blood glucose levels. Foods that contain carbohydrate are given a GI value; foods that have little or no carbohydrates such as cheese, meat, fish and eggs will have no GI value.

Carbohydrate foods that break down quickly during digestion raise blood glucose more quickly, and have a higher GI value (greater than 70). Foods that break down more slowly during digestion raise blood glucose more slowly and have a lower GI value (less than 55).

Mixing foods with different GI values creates a new GI for the meal. Swapping high GI foods for medium or low options may help you to improve your diabetes control, improve cholesterol profile, and help obtain / maintain a healthy weight. When considering how to incorporate the GI into meal planning, consider:

  • Mixing high GI foods with lower GI alternatives will help to lower the GI of the meal for example: High GI Food (Baked Potato) + Low GI Food (Baked Beans) = Medium GI Meal
  • Low GI foods are not always healthy for example ice cream, nuts, chocolate all have a low to medium GI but is high in fat and kilocalories. Such items should be eaten in small quantities.
  • High GI foods can be a good source of nutrients for example watermelon, so do not need to be removed just because they have a rapid and large affect on blood glucose levels.
  • Focus on the overall GI content of your meal to keep blood glucose levels within target range.
  • For a healthy, balanced approach to eating, include low fat and low sugar foods with lower GI options as a basis for meal and snacks

The diagram below demonstrates how low, medium and high GI foods can affect blood glucose over time.


Low, Medium and High GI Foods 

The table below illustrates the GI value of commonly eaten foods and drinks.


Low GI

Less than 55

Medium GI

55 - 70

Higher GI

Greater than 70

Breakfast Cereals

All Bran, Sultana Bran, Muesli, Porridge Oats

Instant Porridge, Weetabix, Shredded Wheat, Special K

Coco Pops, Rice Krispies, Cornflakes, Cheerios

Bread, Biscuits, Cakes, Confectionary

Rye Bread, Pumpernickel Bread,

Granary / Multigrain Bread, Pitta Bread, Wholemeal Bread, Crumpet, Digestive, Rich Tea, Crisps, Chocolate

French Stick, White Bread, Bagel,

Potatoes, Rice, Pasta

Sweet Potatoes, Noodles, Macaroni Spaghetti,

New Potatoes, Boiled Potatoes, Couscous, Brown Rice, Basmati

Instant Potatoes, Baked Potatoes, Instant Rice, French Fries, Chips

Fruit and Vegetables

Apples, Grapefruit, Grapes, Kiwis, Oranges, Peaches, Pears, Carrots, Green Peas

Apricots, Mangoes, Pineapples, Raisins, Sultanas, Melons

Watermelon, Turnip, Parsnips

Beans and Pulses

Baked, Butter, Black, Kidney Beans, Chick Peas, Lentils, Nuts


Broad Beans

Milk and Dairy

Milk, Custard, Yoghurt

Ice Cream


The key is to use the GI in the context of balanced eating. A healthy way to use the GI principles is to incorporate a range of lower GI carbohydrates that are also low in fat and calories into your meals.

Further Information:

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