My 13 year old is taking sucralfate for stomach ache how long should it be before it starts working?

Depends on injury.: Sucralfate is absorbed very minimally and works by coating the lining of the stomach to protect any ulcers or inflammation from the acids in the stomach. It should be taken 4 times a day at least 1 hour before meals to allow for coating of the stomach. Pain relief should occur after a few doses, but if persist after 3 -4 days, contact your doctor for advise regarding your symptoms.