Bananas are a fascinating fruit in terms of their carbohydrate and sugar content. Even though bananas are a fruit that tastes quite sweet when ripe—containing 14-15 grams of total sugar—bananas receive a rating of low in their glycemic index (GI) value. GI measures the impact of a food on our blood sugar. This low GI value for bananas is most likely related to two of their carbohydrate-related qualities.