If you’re trying to avoid sharp spikes in blood sugar, then read food package labels or check for a food’s glycemic index online. The glycemic index (GI) is a number that measures how quickly foods containing carbohydrates raise the amount of sugar in the blood.

In general, foods with a low glycemic index (55 or less) have the least impact on your blood sugar. Foods with a glycemic index of 56 to 69 affect blood glucose levels more, and foods with a GI of 70 or greater boost blood sugar too high.

A food’s GI is affected by a number of factors. For example, how a food is prepared and the ingredients used can lower or increase its glycemic index; ripened fruit has a higher GI; and processed and refined foods register higher glycemic indexes than whole foods.

But remember, nutritionists advise that foods with low GI numbers aren’t necessarily better for you. The overall amount of nutrients a food contains can trump these digits, as well as the quantity of the foods we eat.