Sugars & sweeteners · Glycemic index

Does table sugar spike blood sugar?

Only a little. Table sugar has a medium GI of 66, and a 4.2 g serving (1 teaspoon) has a low glycemic load of 3. Table sugar has a medium GI; a single teaspoon has a low glycemic load, but sugar in drinks, desserts and sauces adds up quickly.

Key numbers

Glycemic index: 66; Medium GI
Glycemic load: 3; Low GL
Available carbs: 4 g; 0 g fiber
Serving: 1 teaspoon; 4.2 g · granulated

GI vs GL for table sugar

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 table sugar: 66 × 4 g ÷ 100 ≈ 3.

That figure is an average reported in the 2021 international GI tables (“Sucrose, mean of seven studies”). Seven studies averaged 66 in the 2021 tables; the 2008 tables gave 65 across six studies.

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

How to eat table sugar with less of a spike

Cut the sugar in coffee or tea gradually — halve it for a couple of weeks, then halve it again.
Sweeten yogurt and oatmeal with berries instead.
Check labels on sauces, cereals and flavored yogurts, where added sugar often turns up.

Lower-GI swaps

Compare with

See all 67 foods in the glycemic index table

Frequently asked questions

What is the glycemic index of table sugar?

Table sugar has a glycemic index of 66, which is medium. That figure is an average reported in the 2021 international GI tables (“Sucrose, mean of seven studies”). A 4.2 g serving (1 teaspoon) contains about 4 g of available carbohydrate, giving a glycemic load of 3 (low).

Is table sugar good for prediabetes?

For prediabetes, the goal is to cut back on added sugar overall rather than to find a 'better' sugar. A teaspoon in coffee is a small load; sugary drinks and desserts are where the carbohydrate piles up.

Why doesn't table sugar have a GI of 100?

Because only half of it is glucose. Sucrose splits into glucose and fructose, and fructose barely raises blood glucose — its average GI was 24 in the 2021 tables — so sucrose's average of 66 sits between the two.

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.