When you reach for a bottle of milk of magnesia, you’re using magnesium hydroxide, a mild base used to neutralize stomach acid and draw water into the intestines. Also known as Mg(OH)₂, it’s one of the oldest and most trusted remedies for heartburn and occasional constipation. Unlike stronger acid blockers, it doesn’t shut down acid production—it just balances it. That’s why it’s often the first choice for people who want quick relief without long-term changes to their digestive system.
But magnesium hydroxide isn’t just an antacid. It’s also a gentle laxative, a substance that helps move stool through the colon by increasing water content. That’s why it’s in many over-the-counter constipation formulas. It works slowly, usually in 30 minutes to 6 hours, and doesn’t cause cramping like some stimulant laxatives. But it’s not for daily use. Too much can lead to diarrhea, electrolyte imbalances, or even kidney stress—especially if you already have kidney problems or take other meds like antibiotics or thyroid pills.
Many people don’t realize that drug interactions, when one medicine changes how another works in the body can turn a harmless remedy into a risk. Magnesium hydroxide can lower the absorption of tetracycline antibiotics, iron supplements, and even some HIV drugs. If you’re on a regular medication, check with your pharmacist before using it. And if you’re using it for more than a week without relief, it’s not a fix—it’s a sign something else is wrong.
It’s also worth noting that magnesium hydroxide is often confused with other magnesium compounds like magnesium citrate or magnesium oxide. They all have magnesium, but they work differently. Citrate is better for constipation, oxide is used for long-term magnesium deficiency, and hydroxide? It’s the go-to for quick, short-term relief. Knowing the difference helps you pick the right one.
There’s no magic here. No fancy science. Just a simple compound that’s been helping people for over a century. But that doesn’t mean you can treat it lightly. Too much, too often, or the wrong combo with other meds can backfire. The posts below cover real cases—people who took it without knowing the risks, others who used it safely alongside other treatments, and what to watch for if you’re on multiple prescriptions. Whether you’re using it for heartburn, constipation, or just curious why your pill looks different this time, you’ll find practical, no-fluff advice here.
Antacids like Tums and Milk of Magnesia can be dangerous for people with kidney disease. Learn how calcium, magnesium, and aluminum in these drugs affect phosphate levels, cause toxicity, and interact with prescription binders - and what to do instead.
