Glycaemic index (GI) and Glycaemic load (GL) are two different but somehow related terms which tell us how consuming a food item will affect the blood glucose levels.

Glycaemic Index (GI)-

• GI is a value assigned to foods based on how slowly or how quickly those foods causes increase in blood glucose levels, rather we can say it tells us the quality of the carbohydrate present in the food product.
• However, the problem with the GI is that it doesn’t provide an accurate picture of the entire blood sugar raising potential of the food, so here glycaemic load comes into the picture.
• Glycaemic Index Ranges- 

        Low        – 55 or less

        Medium – 56-69

        High       – 70 and above

Glycaemic Load (GL)-

• GL is a value obtained by multiplying the quality of carbohydrate in a given food (GI) by the amount of carbohydrate in a serving of that food.
• GL is basically an extension of the GI, taking into account the quantity of carbohydrates as well.
• Glycaemic Load Ranges-

        Low        – 10 or less

        Medium – 11-19

        High       – 20 or above

Relation between Glycaemic Index and Glycaemic Load-

Glycaemic Load = Glycaemic Index * Carbohydrate content of the food in question 

EXAMPLE-

Apple- 

GI = 38

Carbohydrate content = 13g

GL = 38 * 13 / 100 = 5 (Low)

Above example clearly tells us how slowly carbohydrate present in the apple converted into sugar, so if taken in optimum quantity, it will have low glycaemic load on the blood glucose levels. 

Potato-

GI = 85 

Carbohydrate content = 14g

GL = 85 * 14 / 100 = 12 ( High/Medium )

Potato has the quality of carbohydrate which is quickly converted into sugar, so even if taken in optimum quantity, it will have a medium glycaemic load on blood glucose levels and a high glycaemic load if consumed in large quantities.

Note- 

Foods low on GI scale tend to release glucose slowly and steadily, on the contrary, foods high on GI release glucose rapidly.