About to take 300ml of magnesium citrate, as directed by my doctor for constipation. however, how fast should i drink the magnesium citrate & how quickly should i drink the glass of water with it?if i have a decaf latte after taking it, is that okay?

Just drink: Just drink the bottle of magnesium citrate as though you were drinking a bottle of water when thirsty. Follow with bottle of water in similar fashion and relax. There is no problem having decaf latte.

Can take any time: You can drink the magnesium citrate as fast as you want and at any time. I usually recommend at bedtime since magnesium can be calming. I also recommend a daily magnesium capsule to many of my patients for the same reason (constipation and/or sleep). About 200-250 mg is fine and dose can be increased as long as you don't get diarrhea.