Self Magazine's NutritionData explains that half of a large grapefruit that weighs 166 grams contains 12 grams of sugar. Half of a large grapefruit also contains 13 grams of carbohydrates, which is 4 percent of the daily nutritional recommendation.
Self Magazine's NutritionData states that the downside to eating grapefruit is its sugar content. However, if consumed in moderation, grapefruit still has nutritional benefits. For example, grapefruit is low in saturated fat, cholesterol and sodium. It also contains the following recommended nutritional percentages: 7 percent of dietary fiber, 7 percent of potassium, 31 percent of vitamin A and 95 percent of vitamin C.