Most citrus fruits have a low glycemic index so if you are trying to lower post-prandial blood glucose levels, they can be a great choice when selecting fruit. As with all carbohydrate foods, you need to count the carbohydrate in your meal plan.
Serving sizes for 15 grams of carbohydrate are:
1 small nectarine or orange (5 oz)
2 small tangerines (8 oz)
1/2 large grapefruit (11 oz)
3/4 cup canned mandarin oranges
1/2 cup of orange or grapefruit juice