Amy Tenderich was diagnosed with type 1 diabetes in May of 2003. She is the founder and editor-in-chief of Diabetes Mine and co-authored the book Know Your Numbers, Outlive Your Diabetes. You will frequently find her speaking at diabetes, health, and social media events across the country.

Many common carb-loaded foods have similar effects on your blood glucose (BG), but some do have advantages over others. These advantages stem from containing fiber (which slows absorption of the sugar content) and other nutrients, present especially in fruits and vegetables. These extra-beneficial carbohydrates tend to be in the group of foods with a so-called “low glycemic index.”

The glycemic index (GI)

The glycemic index (GI) is an attempt to scientifically determine the impact of individual foods on your BG levels. Here’s how it’s calculated:

To set the GI value of a particular food, say a slice of bread, ten volunteers eat 50 grams (about two ounces) of the bread in the morning after fasting, and their BG is measured over the next two hours. The total rise in glucose during this two-hour time period is calculated. Several days later, the same 10 volunteers drink 50 grams of glucose, and have their BG measured in the same way over the next two hours. Then the two glucose sums are compared, and the difference in value between the test food and the ingested glucose becomes the GI value for the tested food.

You can easily find the GI value of hundreds of foods in a searchable database maintained by the University of Sydney, Australia, at

What’s important to know here is that foods with lower GI values have a lesser impact on your BG in the first two hours after you’ve eaten them. They take longer to absorb into your system, so they are generally good choices for people with diabetes. (Low-GI carbohydrate foods are otherwise known as “slow-acting carbs.”)

Using GI in real life

As simple as it sounds, the glycemic index isn’t so easy to utilize in real life. Foods don’t always affect your BG the way you would expect them to based on their GI value, due to a number of variables:

  • Most of your food is not eaten directly after fasting, as it was during the GI testing.
  • In real life, foods are eaten in various combinations and amounts, and the method of cooking (boiling, grilling, baking) varies.
  • The age of the food also changes the GI impact.

For these reasons, lots of people don’t use the glycemic index but rather work to keep their carb intake down by focusing on eating more fiber, fruits, and vegetables.

It’s also important to know that real, unprocessed foods will always be better for you than any fabricated “low-carb” product. That stuff is often extremely high in fat and chemicals, and has in some cases even been altered specifically to be indigestible so that your so-called “free” chocolate will create a nasty stomachache.

Other tips:

Tip 1: How to Recognize a Carb
Tip 3: How to Avoid Carb Overload
Tip 4: How to Learn and Practice Carb-Counting
Tip 5: What a Nutritionist Can Do for You