Magnesium Hydroxide: What It Is and How It Works

Magnesium hydroxide is a white powder that turns into a weak base when it meets water. In the body it acts like a gentle neutralizer for stomach acid and also pulls water into the intestines to help move stool along. Because it does both jobs, you’ll often see it in over‑the‑counter products for heartburn and constipation.

Common Uses: Antacid and Laxative

When you feel that burning sensation after a big meal, a dose of magnesium hydroxide can quickly calm the pain. The compound reduces acidity by reacting with hydrochloric acid in the stomach, forming magnesium chloride and water. This reaction is mild, so it won’t strip away all stomach acid, which you need for digestion.

On the flip side, if you’re dealing with occasional constipation, magnesium hydroxide works as an osmotic laxative. It draws water into the colon, softening stool and making bowel movements easier. Most products recommend taking it with a full glass of water, and the effect usually kicks in within a few hours.

Safety, Dosage, and When to See a Doctor

For most adults, the standard dose for heartburn is 1 to 2 teaspoons of the liquid form or 2 to 4 tablets of the chewable form. For constipation, the dose may be a bit higher, but you should always follow the label or your doctor’s advice. Taking too much can cause diarrhea, cramping, or an electrolyte imbalance, especially if you have kidney problems.

Kids need a lower dose based on weight, and infants should only use magnesium hydroxide if a pediatrician says it’s safe. If you notice persistent stomach pain, blood in the stool, or you can’t get relief after two days, it’s time to call a health professional.

People on certain medications—like antibiotics, blood pressure drugs, or heart medications—should check with a pharmacist before using magnesium hydroxide. The mineral can interfere with how some drugs are absorbed.

Overall, magnesium hydroxide is a cheap, widely available option for occasional heartburn or constipation. Keep it in a cool, dry place, and replace it if the product looks discolored or passes its expiration date.

Remember, it’s fine for short‑term use, but if you find yourself reaching for it often, talk to a doctor. Chronic heartburn or constipation can signal deeper health issues that need a proper diagnosis and treatment plan.