Ciprofloxacin and Antacids: What You Need to Know About This Dangerous Interaction

When you take ciprofloxacin, a broad-spectrum antibiotic used to treat bacterial infections like urinary tract infections, pneumonia, and skin infections. Also known as Cipro, it works by stopping bacteria from reproducing. But if you’re also taking antacids, over-the-counter medicines like Tums, Rolaids, or Maalox that neutralize stomach acid. Also known as acid reducers, they’re meant to relieve heartburn and indigestion, you could be making your antibiotic useless. This isn’t a minor caution—it’s a well-documented interaction that can turn a simple infection into a serious problem.

The problem? calcium, a mineral found in many antacids that binds tightly to ciprofloxacin in the gut. Also known as Ca²⁺, it forms an insoluble complex that your body can’t absorb, magnesium, another common antacid ingredient that does the same thing. Also known as Mg²⁺, it blocks absorption just like calcium, and aluminum, a third key player in many antacids that traps ciprofloxacin before it even enters your bloodstream. Also known as Al³⁺, it’s the reason why even a single dose of Tums can slash your antibiotic’s effectiveness by up to 90%. Studies from the FDA and clinical journals show that taking these together reduces ciprofloxacin absorption so much that drug levels in your blood drop below what’s needed to kill bacteria. That means your infection won’t clear—and worse, it might come back stronger, with bacteria that are harder to treat.

So what do you do? If you need an antacid, wait at least two hours after taking ciprofloxacin. Or wait four hours before taking the antibiotic. Don’t mix them in the same meal. Same goes for iron supplements, zinc, or multivitamins with minerals—they all interfere the same way. Even dairy products like milk or yogurt can cause issues, though less severely. The key is timing. Many people don’t realize this interaction exists because they think antacids are harmless. But this isn’t about stomach comfort—it’s about whether your antibiotic works at all.

You’ll find real-world advice in the posts below: how to time your doses, what alternatives to antacids won’t mess with your treatment, and how to spot if your infection isn’t responding because of this interaction. Some posts even compare ciprofloxacin with other antibiotics that don’t have this problem, so you know what to ask your doctor about next time. This isn’t theoretical—it’s something that happens every day in clinics and homes. Don’t let a simple mistake cost you your recovery.