There’s no single “best” antacid for everyone. The right choice depends on your specific symptoms, how often you need relief, and whether you have any health conditions that rule out certain ingredients. What all antacids share is a fast mechanism: they neutralize stomach acid directly, providing relief in minutes rather than the hour or more that stronger acid-reducing medications require. The tradeoff is that antacid relief is shorter-lived, typically fading within one to three hours.
How Antacids Work
Antacids contain alkaline minerals that neutralize hydrochloric acid in your stomach. They also block pepsin, the enzyme your stomach uses to break down food. This raises the pH in your stomach enough to stop the burning sensation of heartburn or the discomfort of indigestion. The three most common active ingredients are calcium carbonate, magnesium hydroxide, and aluminum hydroxide. Many products combine two of these to balance out their side effects.
Comparing the Three Main Types
Each mineral base works slightly differently, and each comes with its own quirks.
Calcium carbonate (found in Tums and many store brands) is the most popular choice. It works quickly, tastes relatively mild in chewable form, and delivers a small dose of calcium. The downside: it can cause constipation, and taking too much over time can raise blood calcium levels. Labels typically cap use at 9 tablets per 24 hours for adults (6 if you’re pregnant), and you shouldn’t use the maximum dose for more than two weeks without medical guidance.
Magnesium hydroxide (the active ingredient in Milk of Magnesia and some Rolaids formulations) tends to work a bit faster and has a mild laxative effect. That makes it a reasonable pick if you’re already prone to constipation, but a poor one if loose stools are a concern. People with kidney disease should avoid magnesium-based antacids entirely, because impaired kidneys can’t clear excess magnesium efficiently, allowing it to build to dangerous levels.
Aluminum hydroxide (found in Amphojel and similar products) provides comparable relief but leans in the opposite direction: it’s more likely to cause constipation. This is why many manufacturers combine aluminum and magnesium in a single product, so the two effects roughly cancel each other out.
Alginate Products for Reflux
If your main problem is acid creeping up into your throat, especially when you lie down, an alginate-based product (like Gaviscon) works differently from a standard antacid. When alginates mix with stomach acid, they form a gel-like raft that floats on top of your stomach contents. This physical barrier sits between your stomach and esophagus, keeping acid from splashing upward. Standard antacids neutralize acid that’s already there, but they don’t prevent it from traveling up. For nighttime heartburn or reflux that hits after meals, the raft-forming approach often provides more noticeable relief than a plain calcium or magnesium tablet.
Matching the Product to the Problem
For occasional heartburn after a spicy meal, a basic calcium carbonate chewable is usually the simplest and cheapest option. It starts working within minutes, and you can carry a few tablets in your pocket or bag.
For reflux that worsens when you recline, an alginate combination gives you both acid neutralization and a physical barrier. This is particularly useful if you get symptoms at bedtime.
For frequent heartburn happening more than twice a week, antacids alone are probably not the right tool. H2 blockers take about an hour to kick in but last four to ten hours, making them better suited for predictable, recurring symptoms. If you’re reaching for antacids daily, that pattern itself is worth discussing with a healthcare provider, because chronic acid exposure can damage the esophagus over time.
Side Effects Worth Knowing
Most people tolerate antacids well when used occasionally. The most common complaints are digestive: constipation from calcium or aluminum products, diarrhea from magnesium products. These effects are mild at normal doses but become more noticeable with frequent use.
A less obvious concern is how antacids interact with other medications. Because they change the pH in your stomach and intestines, antacids can interfere with how your body absorbs a surprisingly wide range of drugs. They can either speed up or slow down absorption, or reduce the total amount that makes it into your bloodstream. If you take thyroid medication, certain antibiotics, or other daily prescriptions, spacing them at least two hours apart from any antacid helps avoid this problem.
Special Considerations for Pregnancy
Heartburn is extremely common during pregnancy, and antacids are considered the most appropriate first-line treatment. Calcium carbonate is the most widely recommended option because it’s effective, well-studied in pregnancy, and provides supplemental calcium. The main caution is a lower daily maximum: most labels advise no more than 6 tablets in 24 hours during pregnancy, compared to 9 for other adults.
Use in Children
Over-the-counter antacids formulated for kids are dosed by weight first, then by age if weight isn’t available. Children under 2 years old generally need a doctor’s guidance before taking any antacid. For ages 2 to 5 (roughly 24 to 47 pounds), the typical dose is one pediatric tablet with a maximum of 3 tablets per day. Children 6 to 11 (48 to 95 pounds) can take two tablets at a time, up to 6 per day. As with adults, these products aren’t meant for daily use beyond two weeks without medical supervision.
When Antacids Aren’t Enough
Antacids are designed for short-term, as-needed relief. If you find yourself using them most days, or if your symptoms return as soon as the effect wears off, the issue likely needs a longer-acting approach. H2 blockers and proton pump inhibitors reduce acid production at the source rather than neutralizing it after the fact, which makes them more effective for persistent problems like gastroesophageal reflux disease. Persistent heartburn, difficulty swallowing, or unintentional weight loss alongside digestive symptoms all warrant a closer look beyond the antacid aisle.