Tums contain one active ingredient: calcium carbonate, a mineral compound that neutralizes stomach acid on contact. Depending on the strength you buy, each tablet contains between 500 mg and 1,000 mg of calcium carbonate, along with a handful of inactive ingredients that give the tablets their color, flavor, and chewable texture.
The Active Ingredient: Calcium Carbonate
Calcium carbonate is a naturally occurring mineral found in limestone, chalk, and seashells. In Tums, it serves a dual purpose: it works as an antacid and provides a supplemental dose of calcium. When you chew a tablet, the calcium carbonate reacts directly with hydrochloric acid in your stomach. That reaction produces water, carbon dioxide gas (which you may notice as mild burping), and calcium chloride, a harmless salt your body processes normally.
This reaction happens quickly, which is why Tums can relieve heartburn within minutes. Unlike some other heartburn medications that reduce acid production over hours, calcium carbonate physically neutralizes the acid already sitting in your stomach.
One detail worth knowing: calcium carbonate is only 40% elemental calcium by weight. That means a tablet with 750 mg of calcium carbonate delivers about 300 mg of actual calcium to your body, and a 1,000 mg tablet delivers about 400 mg. If you’re using Tums partly as a calcium supplement, this matters for hitting your daily target.
Inactive Ingredients by Formulation
The inactive ingredients vary by flavor and product line, but most standard Tums tablets share a common base: corn starch, sucrose (table sugar), mineral oil, flavoring agents, and sodium polyphosphate. The flavored versions also contain synthetic food dyes. Cherry tablets use FD&C Red #40. Wintergreen uses a combination of Blue #1 and Yellow #5. The Assorted Fruit variety contains Blue #1, Red #40, Yellow #5 (tartrazine), and Yellow #6 to create its range of colors. Talc appears in most of these formulations as well, and some flavors include adipic acid, which adds a slight tartness.
The Tums Naturals line takes a different approach. These tablets are labeled “no artificial flavors or dyes” and use a noticeably shorter ingredient list: calcium stearate, dextrose, gum arabic, and natural flavors. The Black Cherry and Watermelon variety gets its color from carmine, a pigment derived from cochineal insects. The Coconut Pineapple version skips added color entirely.
Sugar-free versions replace sucrose with sorbitol and sucralose as sweeteners. They also use acacia gum and calcium stearate instead of the corn starch and mineral oil found in regular tablets. If you’re watching sugar intake or managing diabetes, these are the ones to look for.
How Much Sugar Is in Regular Tums
Standard Tums tablets list sucrose as a primary inactive ingredient. Each tablet is small, so the sugar content per tablet is modest, but it adds up if you’re chewing several throughout the day. The label allows up to 15 tablets in 24 hours for non-pregnant adults (10 for pregnant women), which means someone at the maximum dose is consuming a meaningful amount of added sugar. The sugar-free formulations avoid this entirely by using sugar alcohols and artificial sweeteners.
Medications That Don’t Mix Well With Tums
Because calcium carbonate raises your stomach’s pH and binds to certain compounds, it can interfere with how your body absorbs other medications. The list is longer than most people expect. Thyroid hormones, certain antibiotics (fluoroquinolones and tetracyclines), iron supplements, osteoporosis drugs, proton pump inhibitors like omeprazole, and some heart rhythm medications can all be affected.
The issue isn’t that Tums makes these drugs dangerous. It’s that your body absorbs less of the medication, so you may not get the full therapeutic dose. If you take any of these regularly, spacing them at least two hours apart from Tums is the standard recommendation.
Daily Limits and Calcium Concerns
The label on regular strength Tums caps adults at 15 tablets per day, with a lower limit of 10 tablets for pregnant women. These limits exist partly because of the calcium load. Fifteen tablets of extra-strength Tums could deliver over 4,500 mg of calcium carbonate, translating to roughly 1,800 mg of elemental calcium. That’s well above the 1,000 to 1,200 mg most adults need daily, and consistently exceeding that amount can lead to problems like constipation, kidney stones, or in rare cases, a condition where excess calcium disrupts normal kidney and metabolic function.
Occasional use for heartburn is straightforward. But if you find yourself reaching for Tums daily for more than two weeks, the frequency itself is worth paying attention to, as it may signal an underlying condition that antacids alone won’t resolve.