Question: how long does diarrhea last after taking milk of magnesia?
Answer: When taken as a laxative, Milk of Magnesia should produce a bowel movement within 30 minutes to 6 hours. Call your doctor if the condition you are treating with Milk of Magnesia does not improve, or if it gets worse while using this medicine. Do not use Milk of Magnesia for longer than 7 days without medical advice.