Citrus fruits are loaded with vitamins, minerals and dietary fibers which are essential for healthy growth and development of the body. The main reason we get energy from citrus fruits is that they are loaded with carbohydrates. They contain carbohydrates in the form of fructose, glucose and sucrose. A medium grapefruit contains 18.5 grams of carbs and 2.7 grams of fiber. A single serving of oranges contain 14 g of carbohydrates.