The total carbohydrate content of a medium banana is 30 grams, of which 19 grams is in the form of sugar. The remainder is in the form of starch. Click here for more information about bananas. If you are not sure how to fit bananas or other foods into your diet, I would encourage you to speak with a registered dietitian or a certified diabetes educator. You can find a registered dietitian by www.eatright.org.