H2 Blockers: What They Are, How They Work, and What You Need to Know

When your stomach makes too much acid, it can cause heartburn, ulcers, or reflux. That’s where H2 blockers, a class of medications that reduce stomach acid by blocking histamine receptors in the stomach lining. Also known as histamine H2 receptor antagonists, they work fast and are often used when antacids aren’t enough. Unlike proton pump inhibitors (PPIs), which shut down acid production more completely, H2 blockers give you targeted, shorter-term relief—perfect for occasional heartburn or nighttime symptoms.

These drugs don’t just treat discomfort—they help heal damage. If you’ve been diagnosed with a stomach or duodenal ulcer, your doctor might prescribe an H2 blocker to let the tissue repair itself. They’re also used for Zollinger-Ellison syndrome, a rare condition where tumors cause extreme acid overproduction. And while you might think of them as just for heartburn, they’ve been part of everyday medicine for decades. Famotidine (Pepcid), ranitidine (Zantac), and cimetidine (Tagamet) are the big names. But here’s the catch: ranitidine, once a top-selling H2 blocker, was pulled from the market in 2020 after concerns about a cancer-causing contaminant called NDMA. Also known as Zantac, it’s no longer available in the U.S. or most countries. That left people looking for safer, just-as-effective alternatives. Today, famotidine is the go-to H2 blocker, and it’s still widely used in both prescription and over-the-counter forms.

What about side effects? Most people tolerate H2 blockers well. But some report headaches, dizziness, or diarrhea. Long-term use can affect vitamin B12 absorption or kidney function in older adults. That’s why they’re not meant to replace lifestyle changes—like avoiding spicy food, not eating before bed, or quitting smoking. They’re a tool, not a fix. And if you’re taking other meds, especially blood thinners or antifungals, check with your pharmacist. H2 blockers like cimetidine can interfere with how your body processes certain drugs.

There’s a reason H2 blockers still show up in 2025 health guides—even as PPIs dominate the market. They’re fast, affordable, and work well for people who don’t need daily acid suppression. If you’ve been told to take a PPI for months but only get relief at night, an H2 blocker before bed might be all you need. Or maybe you’re trying to cut back on long-term PPI use. Many doctors recommend switching to an H2 blocker temporarily to reduce dependency.

Below, you’ll find real posts from people who’ve used these drugs, compared them to other treatments, and learned what works—and what doesn’t. From how they interact with other medications to why some people avoid them entirely, the insights here aren’t theory. They’re lived experience.