How long does Aluminum Hydroxide and Magnesium Hydroxide take to work?
Last updated September 7, 2026.
Aluminum hydroxide and magnesium hydroxide usually starts working within about 5 minutes, because it neutralizes acid that is already sitting in your stomach rather than shutting off acid production. How long the relief lasts depends mostly on timing: on an empty stomach the dose leaves the stomach quickly and may last only 20 to 60 minutes, while a dose taken about an hour after eating can last up to roughly 3 hours. The liquid form generally coats the stomach faster than tablets, and tablets need to be chewed completely rather than swallowed whole. This medicine treats symptoms as they happen, so it does not build up over days the way an acid reducer like famotidine or omeprazole does. If you are reaching for it most days for more than 2 weeks, that pattern is worth a conversation with a clinician instead of a bigger dose.
What to do
- Time it with meals: Taking a dose about 1 hour after eating and again at bedtime stretches relief closer to 3 hours.
- Prepare the dose properly: Shake the suspension hard before measuring, and chew tablets completely instead of swallowing them whole.
- Separate your other medicines: Take antibiotics, iron, and thyroid medicine at least 2 hours apart from this antacid so absorption is not blocked.
- Watch your stools: The magnesium tends to loosen stools and the aluminum tends to firm them up, so tell a clinician if either side takes over.
- Ask first with kidney disease: Reduced kidney function lets magnesium and aluminum build up, so check before using this product regularly.
- Set a 2 week limit: If heartburn keeps coming back past 2 weeks of antacid use, get evaluated instead of increasing the dose.
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