The glycemic index (GI) of a food is a measure of its ability to increase your blood glucose level. A higher GI means that the food increases your blood glucose level more quickly. Diabetics must be especially cautious about eating foods with a high GI to avoid a spike in their blood sugar levels. You'll need to know the amount of carbohydrates in each type of food in your meal to measure the GI of the entire meal.
Step 1
Obtain the number of grams of carbohydrates in each food of your meal. This information is routinely provided on the nutritional labels of prepared food.
Step 2
Compute the total grams of carbohydrates in the meal. Assume for this example that the meal consists of milk with 20 grams of carbohydrates, toast with 30 grams of carbohydrates and shredded wheat with 40 grams of carbohydrates. This meal therefore has a total of 90 grams of carbohydrates.
Step 3
Calculate the percentage of total carbohydrates provided by each food in your meal. The milk has 20 grams of carbohydrates, so it provides 22.2 percent of the carbohydrates in your meal. The toast has 30 grams of carbohydrates, so it provides 33.3 percent of the carbohydrates in your meal. The shredded wheat has 40 grams of carbohydrates, so it provides 44.4 percent of the carbohydrates in your meal.
Step 4
Use the GI database on the website Glycemicindex.com to find the GI of each food in your meal. Multiply the GI of each food by the percentage of carbohydrates in the meal provided by that food. Milk has a GI of 32, so its GI value for this meal is 7.1. Toast has a GI of 70, so its GI value for this meal is 23.3. Shredded wheat has a GI of 63, so its GI value for this meal is 28.
Step 5
Add the partial GI values together to find the total GI for the meal. The milk in this meal has a GI value of 7.1, the toast has a GI value of 23.3 and the shredded wheat has a GI value of 28. The total GI value for the meal is 58.4.
Things You'll Need
- Calculator
- Glycemic index chart
