Magnesium Hydroxide: What It Is, How It Works, and What You Need to Know

When you reach for a bottle of milk of magnesia to calm a sour stomach or ease constipation, you’re using magnesium hydroxide, a simple compound that neutralizes stomach acid and draws water into the intestines. Also known as Mg(OH)₂, it’s one of the oldest and most trusted remedies for digestive discomfort. Unlike fancy new supplements, this isn’t a trend—it’s a proven, low-cost solution that’s been used for over a century.

Magnesium hydroxide works in two clear ways: as an antacid, it neutralizes excess stomach acid to relieve heartburn and indigestion, and as a laxative, it pulls water into the colon to soften stool and trigger bowel movements. That’s why you’ll find it in products like Milk of Magnesia, Di-Gel, and many generic OTC formulas. It doesn’t just mask symptoms—it fixes the root issue: too much acid or too little movement in the gut.

People use it for short-term relief, not daily maintenance. Taking it too often can lead to diarrhea, electrolyte imbalances, or even dependency. It’s not meant for long-term use like proton pump inhibitors, but for when you need fast, reliable help—like after a heavy meal or during travel. It’s also a common choice for older adults who struggle with constipation from other medications, or anyone avoiding stronger laxatives.

What you won’t find in most drugstores is how it compares to other magnesium forms. Magnesium citrate, oxide, or glycinate each serve different purposes—citrate is better for absorption, glycinate is gentler on the gut, and oxide is often used for constipation. Magnesium hydroxide sits right in the middle: strong enough to work fast, but not always the best for long-term magnesium levels. If you’re taking it for heartburn, fine. If you’re trying to boost your overall magnesium, you might need something else.

It’s also worth noting that magnesium hydroxide can interact with other drugs. Antibiotics like tetracycline, iron supplements, and thyroid meds can be less effective if taken at the same time. Always space them out by a few hours. And if you have kidney problems, talk to your doctor first—your body might not clear the extra magnesium safely.

Behind every bottle of milk of magnesia is a simple truth: sometimes the best solutions are the oldest ones. You don’t need a complicated regimen or expensive supplements to feel better. Magnesium hydroxide delivers quick, direct results when you need them most. Below, you’ll find real stories and practical guides on how people use it—along with alternatives, dosing tips, and what to watch out for. Whether you’re using it once a month or helping a loved one manage chronic issues, there’s something here that applies to you.