Antacids and Kidney Disease: What You Need to Know About Phosphate Binders and Risks

Many people reach for antacids like Tums or Milk of Magnesia when they feel heartburn or indigestion. But if you have kidney disease, what seems like a harmless fix could be dangerous - even life-threatening. The problem isn’t just the heartburn. It’s what those antacids do to your body when your kidneys can’t keep up.

Why Antacids Are Used in Kidney Disease

When your kidneys start to fail, they lose the ability to remove excess phosphate from your blood. High phosphate levels can weaken your bones, damage your heart, and cause calcification in your blood vessels. That’s where antacids come in - not as heartburn relievers, but as phosphate binders.

Calcium carbonate (Tums), aluminum hydroxide, and magnesium hydroxide don’t just neutralize stomach acid. They bind to phosphate in your food before it gets absorbed. That’s why doctors sometimes prescribe them to people with chronic kidney disease (CKD), especially in stages 3 and 4. They’re cheap, easy to get, and work - at least for a while.

But here’s the catch: these same antacids can build up in your body if your kidneys aren’t filtering properly. And that’s where things go wrong.

The Hidden Dangers of Calcium-Based Antacids

Calcium carbonate is the most common OTC antacid used as a phosphate binder. It’s effective and affordable - a box of 100 tablets costs less than $5. But for someone with advanced kidney disease, it’s a ticking time bomb.

Your kidneys normally keep calcium levels in check. When they fail, calcium from antacids doesn’t get cleared. Instead, it builds up. Serum calcium above 10.2 mg/dL increases your risk of heart attacks and strokes by 30-50%, according to studies in the Journal of the American Society of Nephrology. One patient on Reddit shared how they took Tums daily for six months, only to find out their calcium level had hit 11.2 mg/dL - and a CT scan showed new calcium deposits in their arteries.

Doctors may start CKD stage 3 patients on calcium carbonate, but only if their phosphate is under control and they have no signs of vascular calcification. Once GFR drops below 30 mL/min, most nephrologists stop calcium-based binders entirely. That’s because the risk of calcification outweighs the benefit of lowering phosphate.

Magnesium: The Silent Threat

Milk of Magnesia (magnesium hydroxide) is often used for constipation - a common problem in kidney patients. But it’s also a potent antacid. And it’s extremely risky if your kidneys can’t clear magnesium.

Healthy kidneys remove excess magnesium through urine. In CKD stage 4 or 5, that system breaks down. Magnesium builds up. At levels above 4 mg/dL, you might feel weak or dizzy. Above 10 mg/dL, you could stop breathing. There are documented cases of dialysis patients ending up in the ER with magnesium levels over 15 mg/dL after taking OTC magnesium hydroxide for constipation.

The National Kidney Foundation warns: “Magnesium-containing antacids should be avoided in patients with CKD stage 4 or 5.” Yet, a 2022 survey by the American Association of Kidney Patients found that 42% of CKD patients had used magnesium-based antacids without telling their doctor.

Aluminum: The Forbidden Antacid

Aluminum hydroxide was once a go-to phosphate binder. It’s very effective - but also incredibly toxic.

Aluminum doesn’t get cleared by failing kidneys. It accumulates in your bones, brain, and blood. Levels above 40 mcg/L can cause bone pain and fractures. Above 60 mcg/L, it leads to dialysis dementia - a condition where patients lose memory, speech, and coordination. The FDA banned aluminum antacids for long-term use in 1990, and since then, they’ve been restricted to short-term use only - no more than two weeks - and never for people with creatinine clearance below 30 mL/min.

Still, some patients use old bottles of aluminum-based antacids they found in their medicine cabinet. Others get them from family members who don’t know the risks. A 2022 review in the Clinical Journal of the American Society of Nephrology found that 57% of emergency visits related to antacids in CKD patients involved aluminum or magnesium products.

Prescription Phosphate Binders: Safer, But Costly

There are better options - but they’re not cheap.

Sevelamer (Renagel) and lanthanum carbonate (Fosrenol) bind phosphate without adding calcium or aluminum. They’re safer for advanced CKD. But a month’s supply can cost $2,000-$4,000. That’s why many patients stick with Tums - especially if they’re uninsured or underinsured.

In a 2018 NEJM study, CKD stage 4 patients on calcium carbonate had a 40% higher risk of hypercalcemia than those on sevelamer. Yet, 82% of low-income patients in one survey said they used calcium carbonate as their main phosphate binder because their insurance wouldn’t cover the prescription alternatives.

Sucroferric oxyhydroxide (Velphoro) is another option. It works with fewer pills - just one or two per meal instead of six. But it costs about $4,000 a month. For many, it’s out of reach.

How to Use Antacids Safely With Kidney Disease

If you have kidney disease, here’s what you need to know:

• CKD Stage 3 (GFR 30-59): Calcium carbonate may be used under supervision. Take it with meals. Do not exceed 1,200 mg elemental calcium per meal. Get your calcium and phosphate levels checked monthly.
• CKD Stage 4-5 (GFR <30): Avoid all OTC antacids as phosphate binders. Use only prescription binders under a nephrologist’s care. If you need heartburn relief, use calcium carbonate occasionally - and only if your doctor says it’s safe. Take it at least two hours before or after your phosphate binder.
• Avoid magnesium and aluminum antacids completely. Even if you think you’re just using it for constipation.
• Check all medications. Antacids can interfere with antibiotics, thyroid meds, and seizure drugs. Take other pills one hour before or four hours after an antacid.

What to Watch For: Symptoms of Toxicity

You don’t need a lab test to know something’s wrong. Watch for these signs:

• High calcium: Nausea, vomiting, confusion, excessive thirst, frequent urination.
• High magnesium: Muscle weakness, dizziness, low blood pressure, slow breathing, paralysis.
• Aluminum toxicity: Bone pain, memory loss, speech problems, seizures.

If you notice any of these, stop the antacid and call your doctor immediately. Don’t wait.

Why So Many Patients Get It Wrong

The problem isn’t just the drugs - it’s the confusion.

A 2022 survey found that 68% of CKD patients couldn’t tell the difference between a prescription phosphate binder and an OTC antacid. Many think Tums and Renagel are the same thing. They’re not.

Primary care doctors often don’t know the risks. One patient said her PCP told her to take Tums for heartburn - never mentioning her kidney disease. Another was given Milk of Magnesia for constipation by an ER doctor who didn’t check her kidney function.

The American Nephrology Nurses Association launched a campaign called “Know Your Binders” in January 2023. Early results show a 28% drop in inappropriate antacid use in clinics that used it. Education saves lives.

What’s Next: New Treatments and Better Guidelines

The FDA approved tenapanor (Xphozah) in 2023 - a new type of phosphate-lowering drug that works differently. Instead of binding phosphate, it blocks its absorption in the gut. It doesn’t carry the same risks as antacids. But it’s still expensive, and long-term data is limited.

The NIH is funding a five-year study called ASK-D, tracking 5,000 CKD patients to create clearer rules on antacid use. And by 2025, the FDA may require separate labeling for antacids sold to kidney patients - making it clear which ones are safe and which are not.

In the meantime, the safest choice is simple: don’t take antacids for phosphate control unless your nephrologist tells you to. And if you’re taking them for heartburn, make sure your doctor knows.