Sex is exercise, just like running or swimming. Like all exercise, the number of calories you burn making love depends on the duration and intensity of the activity, as well as your weight (the more you weigh, the more calories you burn doing the same activity). The average caloric consumption during lovemaking has been calculated at 250 calories an hour.
If your blood glucose tends to go low during sex or immediately after, you might want to check your level just before or after you make love. If you are low or headed in that direction, it's best to eat something. This can briefly interrupt your loving interlude, but it can also help prevent the more serious interruption of a low glucose episode.