It takes about thirty minutes for circulating melatonin to become inactive after the sun rises or lights are turned on. During that time there may be drowsiness, which subsides and does not interfere with daytime functioning. The formula also contains organic dextrose. Diabetics should be aware that 2 tablespoons contain the same amount of carbohydrate as one slice of dry toast. Finally, patients taking drugs that already cause drowsiness, such as antidepressants (pharmaceutical grade or natural such a St. John’s Wort) or lithium, should avoid use.