Tagatose has very similar sweetness to sugar while its glycemic index (GI 3) is very low. GI is a measure of the effects of carbohydrates in food on blood sugar levels. It estimates how much each gram of available carbohydrate (total carbohydrate minus fiber) in a food raises a person's blood glucose level following consumption of the food, relative to consumption of glucose. Glucose has a glycemic index of 100, by definition, and other foods have lower glycemic index. Sucrose has a GI of 68, fructose is 24, and tagatose has very low GI compared with other sweeteners.