What’s The Difference Between Glycemic Index and Glycemic Load?

If you’re living with diabetes, you probably already know the importance of limiting carbohydrates in your diet. But not all carbohydrate rich foods are the same and they don’t all impact your blood sugar in the same way. That’s why science and medicine have come up with two ways to help you understand how various foods elevate blood sugar.

First came the Glycemic Index (GI) and, more recently, a figure called Glycemic Load (GL) was introduced (as if managing diabetes wasn’t challenging enough, they had to throw two ways to measure carbohydrates in food at you). The thing is both have their merits and, if nothing else, you should understand the difference between the two because knowing how they work just might help you better manage your blood sugar.

What is the Glycemic Index?

The glycemic index is a numerical method of classifying foods by the glycemic response they are likely to cause. In other words, how dramatically they are likely to cause your blood sugar to rise.

The glycemic index is measured on a scale of 1 to 100 with pure glucose (sugar) accounting for the value of 100. The GI is benchmarked on how 50 grams of carbohydrates within a given food will increase blood sugar. The lower the number on the scale, the slower and less intense the rise in blood sugar will be after eating that particular food. To further narrow things down, the glycemic index is divided into three primary categories.

  1. Low – foods that measure 55 or less on the index
  2. Medium – foods that measure between 56-69 on the index
  3. High – food that hit 70 or above on the index.

As examples, white bread is at 75 on the glycemic scale and we know why. There are lots of carbs in this processed food. Chickpeas, on the other hand, are at 28 on the glycemic index and popcorn is somewhere in the middle at 65.

The Flaw In The Glycemic Index

Using the glycemic index can certainly help you plan a diabetes friendly diet by pointing out which foods are likely to spike blood sugar. However, there’s a catch and that is this – the glycemic index only tells you how much 50 grams of carbohydrates in a food can spike blood sugar. It does not consider the quantity or portion you’re likely to be eating. In other words, a food that scores high on the glycemic index might be perfectly okay to eat if the number of carbs in an average serving are well below 50 – which brings us to the Glycemic Load.

What is Glycemic Load?

Glycemic load is a newer method of measuring blood sugar response that takes the glycemic index one step further. Rather than using 50grams of carbohydrates as a benchmark, the GL measures blood sugar response against the average serving size of a food and the carbs within that serving that a person is likely to consume. Determining The GI is a simple formula:

Glycemic Index  x  carb content of food in an average serving ÷ 100

This is far more accurate in determining how your blood sugar will actually react when you eat a specific food and Watermelon is the perfect example.

The glycemic index of watermelon is high at 72. But remember that’s based on a volume of watermelon that would give you 50g of carbohydrates. Here’s the thing. The average serving size of watermelon is about 100 grams and contains only about 5 grams of carbohydrates. After all, watermelon is mostly water! So, you’d have to eat ten times the serving size to reach the carbohydrate level measured in the glycemic index. So, what’s the GL of watermelon? Take its GI – 72 – multiply it by the carbs in an average serving – 5 grams – and divide by 100. You come up with a GL of 3.6, which is very low.

Like the glycemic index, glycemic load is divided into three categories.

  1. Low – A GL score measuring 10 or less
  2. Medium – A GL score between 11 - 19
  3. High – A GL score of 20 or higher

Therefore, you can eat more than two servings of watermelon and still be in the low range based on glycemic load! That’s a big difference when compared to the glycemic index of watermelon which tells you this is a sugar-spiking food.

Which one should you follow?

Clearly glycemic load is a more true-to-life measurement because it actually considers the portion size, you’re most likely to consume. But the two are still intertwined. In general, if a food has a low GI, it will also have a low GL.

The difference really comes into play when examining foods that have a high GI or a low GI because that number can be deceiving. The portion size of a high GI food may be far less than what it takes to reach the 50 grams of carbohydrate needed to measure GI (as in our watermelon example). Conversely, it’s possible that a low GI score may be based on a much smaller serving size than you would actually eat, which means blood sugar could spike even with that lower GI score.

There’s still debate over both GI and GL

A post by the Harvard Medical School is quick to point out that while many nutrition experts believe those with diabetes should pay attention to both glycemic index and glycemic load scores, the American Diabetes Association (ADA) says that the total carbohydrate content of a food is a stronger prediction as to what will happen to blood sugar after consuming it. There is also the argument that focusing GI and GL scores can be a rather confusing proposition that adds an unnecessary layer of complexity to creating a diabetes-healthy diet. After all, this is something doctors, nutritionists and tools like the “diabetes plate method” make far easier.

So, what’s the verdict? There’s no reason you shouldn’t consider both glycemic index and glycemic load when monitoring your diet. They can surely help you control blood sugar. However, things like losing weight, being active, testing your blood sugar regularly, and following your doctor-prescribed treatment plan might be easier and a lot more effective ways to manage diabetes for many individuals.


We hope you found this post interesting and informative. At Diabetic Warehouse, we committed to keeping you up to date with the latest topics and unique insights on living with diabetes. We’re also proud to help you stick to your doctor-prescribed diabetes treatment plan with a huge selection of diabetic supplies and equipment at prices up to 65% less than you’ll find at pharmacies and other suppliers.

Diabetic Warehouse is a trusted supplier of diabetes care products and accessories. For more information and to explore a complete range of products, including glucose meters and test strips, insulin syringes, pen needles, continuous glucose monitoring systems, and more, visit

1 THOUGHTS ON “Glycemic Index versus Glycemic Load”

by Stephen Henry

I love the information you present!