Grapes contain natural sugar, but they’re considered a low glycemic index (GI) food. This means a single serving is unlikely to raise your blood sugar significantly. But raisins are another story.

The sugar in raisins becomes concentrated during the dehydration process. This raises their GI level to moderate. The American Diabetes Association encourages eating fresh fruit as part of a healthy diet. Dehydrated fruits like raisins should be eaten in moderation.