Magnesium Hydroxide: Uses, Safety, and What You Need to Know

When working with magnesium hydroxide, an over‑the‑counter antacid and laxative that neutralizes stomach acid and relieves constipation. Also known as Milk of Magnesia, it offers a dual action for digestive comfort. As a antacid, it raises gastric pH to alleviate heartburn, acid reflux, and indigestion, it directly counteracts excess hydrochloric acid in the stomach. The same compound works as a laxative, drawing water into the colon to soften stool and promote regular bowel movements. This dual‑function makes magnesium hydroxide a go‑to relief for people who experience both reflux and occasional constipation. The basic chemistry is simple: magnesium ions combine with hydroxide ions, creating a neutralizing solution that is safe for short‑term use. Because it’s sold as a liquid, chewable tablet, or powder, you can pick the format that fits your routine, whether you’re at home or on the go. magnesium hydroxide remains a staple in many medicine cabinets for precisely this reason.

When to Use It and Who Should Be Cautious

For most adults, the standard dose is 1–2 teaspoons of liquid or 2–4 tablets every 4–6 hours, not exceeding the label’s maximum daily amount. Pediatric use, however, follows stricter guidelines. In the pediatric use, the dosage is calculated by weight, typically 0.5 mL per kilogram of body weight for infants and toddlers. Parents should always check the product label and consult a pediatrician before giving it to children under two years old. The safety profile is good when used as directed, but overuse can lead to electrolyte imbalance, especially low calcium levels, because magnesium competes with calcium absorption. People with kidney disease need to be extra careful since their bodies may not clear excess magnesium efficiently, raising the risk of hypermagnesemia. Also, magnesium hydroxide can interact with certain antibiotics (like tetracyclines) and heart medications (such as digoxin), reducing their absorption. Checking with a pharmacist or your doctor before combining it with other prescriptions is a smart move.

Beyond everyday heartburn and constipation, magnesium hydroxide shows up in a few niche scenarios. It’s sometimes added to oral contrast agents for imaging studies to protect the stomach lining, and it can be part of a bowel‑preparation regimen before colonoscopy. In these cases, the timing and dosing differ from typical OTC use, so following the clinician’s instructions is crucial. The drug’s rapid onset—usually within 30 minutes for heartburn relief—makes it a handy rescue option, but it isn’t meant for chronic management. If you find yourself reaching for magnesium hydroxide more than twice a week, it may signal an underlying digestive issue that needs professional evaluation. The articles below dive deeper into related topics, from the science behind antacids to safe buying tips for other over‑the‑counter meds, giving you a broader view of how these everyday products fit into overall health.