Mg(OH)2: What It Is, How It Works, and When to Use It

If you’ve ever taken a pink liquid for heartburn or a chewable tablet for constipation, chances are you used magnesium hydroxide – the chemical name Mg(OH)2. It’s basically a double‑acting mineral that neutralizes stomach acid and draws water into the bowels to ease stool passage.

Because it’s cheap, widely available, and generally gentle, Mg(OH)2 shows up in many over‑the‑counter products like Milk of Magnesia, Alka‑Melt, and various pediatric antacids. But it’s not just a one‑trick pony; doctors sometimes prescribe it for kidney stone prevention or as a phosphate binder.

Medical Uses of Mg(OH)2

The two biggest jobs for magnesium hydroxide are acting as an antacid and a laxative. As an antacid, it reacts with hydrochloric acid in the stomach to form magnesium chloride and water, which raises pH and relieves burning sensations. You’ll see doses ranging from 0.5 g to 2 g per serving for occasional heartburn.

When used as a laxative, Mg(OH)2 works by osmosis – it pulls fluid into the intestines, softening stool and stimulating peristalsis. The typical adult dose is 1–2 tablespoons of liquid or 2–4 chewable tablets taken at bedtime, giving you relief the next morning.

Beyond those, some clinicians recommend magnesium hydroxide for hyperphosphatemia in patients with chronic kidney disease because it binds phosphate in the gut. The dosage is higher and must be monitored by a healthcare professional.

How to Take Mg(OH)2 Safely

First, always read the label. Over‑dosing can cause diarrhea, electrolyte imbalance, or even magnesium toxicity if you have kidney problems. If you’re on prescription meds like antibiotics or heart drugs, check with your pharmacist – Mg(OH)2 may interfere with absorption.

Take it with a full glass of water unless the product is already liquid. For antacid use, you can repeat the dose every 2–4 hours, but don’t exceed the daily maximum listed on the packaging (usually around 5 g). For laxative purposes, limit to one night’s dose; using it nightly may make your bowels dependent.

If you’re pregnant or nursing, magnesium hydroxide is generally considered safe, but stick to the lowest effective amount and talk to your doctor first. Children under 2 years should only use pediatric formulations and dosage must be strictly followed.

Watch out for side effects: cramping, excessive gas, or a chalky taste are common. Persistent diarrhea, muscle weakness, or irregular heartbeat signal you need medical help right away – those could mean too much magnesium in your system.

Store Mg(OH)2 products in a cool, dry place and keep them out of reach of kids. If the liquid turns cloudy or the tablets break apart, discard them; stability can degrade over time.

In short, Mg(OH)2 is a handy, inexpensive tool for occasional heartburn and constipation when you follow dosing guidelines. Use it responsibly, stay aware of interactions, and you’ll get relief without unwanted surprises.