Breads · Glycemic index

Does whole-wheat bread spike blood sugar?

Not much in a small portion. Whole-wheat bread has a high GI of 75, but a 32 g serving (1 slice) has a low glycemic load of 9. Surprisingly, most whole-wheat bread has about the same GI as white bread, because the whole grain is milled into fine flour. Its advantages are extra fiber and nutrients rather than a smaller spike.

Key numbers

Glycemic index: 75; High GI
Glycemic load: 9; Low GL
Available carbs: 12 g; 1.9 g fiber
Serving: 1 slice; 32 g · fresh

GI vs GL for whole-wheat bread

The glycemic index (GI) compares how fast the carbohydrate in a food raises blood sugar against pure glucose (100), using a fixed amount of carbohydrate. The glycemic load (GL) adds the other half of the story — how much carbohydrate a normal serving actually contains: GI × available carbs ÷ 100. For whole-wheat bread: 75 × 12 g ÷ 100 ≈ 9.

That figure is an average reported in the 2021 international GI tables (“Wholemeal wheat flour bread, mean of eight foods”). In the 2008 tables, 10 wholemeal breads averaged 74 — essentially the same as white bread. Two stoneground wholemeal loaves tested lower, at 59 and 66.

Eating a different amount? Work out the glycemic load of your portion.

How to eat whole-wheat bread with less of a spike

Look past the 'whole wheat' label to the texture: dense loaves with visible grains and seeds tested lower than soft, finely milled ones.
Choose stoneground whole-wheat bread when you can find it; two stoneground loaves tested 59 and 66 in the 2008 tables.
Keep it to one or two slices and pair it with protein such as eggs or canned fish.

Lower-GI swaps

Compare with

See all 67 foods in the glycemic index table

Frequently asked questions

What is the glycemic index of whole-wheat bread?

Whole-wheat bread has a glycemic index of 75, which is high. That figure is an average reported in the 2021 international GI tables (“Wholemeal wheat flour bread, mean of eight foods”). A 32 g serving (1 slice) contains about 12 g of available carbohydrate, giving a glycemic load of 9 (low).

Is whole-wheat bread good for prediabetes?

Whole-wheat bread beats white for fiber, but don't expect it to spike less. For a lower GI, look for dense breads with visible whole grains or seeds, or for rye.

Why doesn't whole-wheat bread have a lower GI than white bread?

Because the grain is ground into fine flour. Harvard's Nutrition Source notes that finely ground grain is digested more rapidly than coarsely ground grain, which is why intact whole grains beat whole-grain bread. In the 2021 tables, wholemeal bread averaged 75 and white bread 73.

Sources

GI values come from the international GI tables; carbohydrate and fiber per serving are calculated from USDA FoodData Central.

Data last checked September 30, 2026.