The glycemic index (GI) ranks carbohydrate foods by how quickly they raise blood sugar compared with pure glucose, which scores 100. A food with a GI of 30 raises blood sugar slowly; a food with a GI of 90 raises it almost as fast as glucose itself.
Low GI: 55 or less · Medium GI: 56–69 · High GI: 70 or more
See the values for 278 foods on our glycemic index chart.
How GI is measured
Volunteers eat a portion of a food containing a set amount of carbohydrate, usually 50 g, and their blood sugar is measured over the next two hours. That response is compared with their response to the same amount of pure glucose. The average across the group becomes the food’s GI.
Because the test needs a meaningful amount of carbohydrate, foods with very little, like meat, fish, eggs, oils, and most non-starchy vegetables, don’t have a GI. For blood sugar, that’s a good thing.
What changes a food’s GI
| Factor | Example |
|---|---|
| Processing | Steel-cut oats 52, rolled oats 55, instant oats 79 |
| Cooking method | Sweet potato boiled 63, baked 94 |
| Cooking time | Spaghetti al dente 38, softer-cooked average 49 |
| Ripeness | Banana slightly green 42, ripe 51, overripe 58 |
| Type of starch | Basmati rice 58, jasmine rice 89 |
| Fermentation | Sourdough 54, white bread 75 |
| Fat and protein | Potato chips 56, baked potato 85 |
GI vs. glycemic load
GI describes the type of carbohydrate; it doesn’t account for how much you eat. Glycemic load (GL) does, by multiplying GI by the carbs in a serving. Watermelon has a high GI (76) but a GL of only 5 per slice, while spaghetti has a low GI (49) but a high GL (24) per plate. More in glycemic load vs. glycemic index.
How to use the glycemic index
- Swap within food groups. Sourdough for white bread, basmati for jasmine, rolled oats for cornflakes.
- Build meals, not single foods. Protein, fat, and fiber lower the effect of the whole meal.
- Watch portions. A big serving of a low-GI food can still carry a high GL.
- Don’t judge health by GI alone. Chocolate and ice cream test low because of their fat. GI is one tool, not a full nutrition score.
Where to start
- Complete glycemic index chart
- Low GI food list
- How to follow a low glycemic diet
- Food lists for South Beach, keto, Mediterranean and more
This page is general information, not medical advice. Last reviewed October 2026.
i like to know why glycemic index of conflakes is high?
please reply as soon as possible
How do I determine the GI value of food (specifically Fiber One Cereal) not on the list?