Can famotidine cause health problems? Understanding the risks and side effects

October 13, 2025 •

4 min read

While generally safe for short-term use, famotidine can cause health problems in some individuals, particularly those with kidney issues or the elderly. Understanding the specific risks associated with this common over-the-counter and prescription medication is crucial for safe usage.

Quick Summary

Famotidine can cause side effects ranging from mild issues like headaches and dizziness to rare but serious health problems, including central nervous system effects, heart rhythm abnormalities, and low blood counts. Risk increases with higher doses, prolonged use, and in those with pre-existing kidney disease or other sensitivities.

Key Points

Central Nervous System (CNS) Risks: Famotidine can, in rare cases, cause confusion, hallucinations, and seizures, especially in elderly patients and those with kidney issues.
Cardiac Concerns: In very rare instances, famotidine has been linked to Long QT syndrome, a condition that can cause an irregular heart rhythm.
Kidney Impairment Increases Risk: Since famotidine is partially eliminated by the kidneys, those with moderate to severe kidney disease are at a higher risk for adverse effects due to drug accumulation.
Limited Duration for OTC Use: Over-the-counter famotidine should not be used continuously for more than 14 days without a doctor's supervision.
Drug Interactions: Famotidine can decrease the absorption of medications that require stomach acid, making them less effective.
Signs of Internal Bleeding: Seek immediate medical attention if you experience bloody vomit or black, tarry stools, as these can signal a more serious problem.

Famotidine is a histamine-2 (H2) blocker used to reduce the amount of acid produced in the stomach. It is a popular over-the-counter and prescription medication for treating conditions like heartburn, acid reflux (GERD), and stomach ulcers. While considered safe for most people when used as directed, it is important to be aware of the potential health problems associated with famotidine, especially for certain high-risk groups.

Common and Mild Side Effects

For most users, famotidine side effects are mild and temporary. These issues often resolve on their own as the body adjusts to the medication. The most frequently reported mild side effects include:

Headache
Dizziness
Diarrhea
Constipation
Nausea and vomiting
Abdominal discomfort
Dry mouth
Fatigue or weakness

If these symptoms persist or become bothersome, it is important to speak with a healthcare provider. Taking famotidine with food can sometimes help mitigate certain side effects like nausea.

Rare but Serious Health Problems

Though uncommon, famotidine can lead to more serious health complications. These are often more likely with higher doses, in individuals with certain pre-existing conditions, or during prolonged use.

Central Nervous System (CNS) Effects

Central nervous system side effects are rare but can be particularly concerning for elderly patients and those with kidney problems, as their bodies may clear the drug more slowly. Reported CNS effects include:

Confusion
Hallucinations
Agitation or delirium
Seizures
Lethargy and unusual drowsiness

Cardiac Complications

In very rare instances, famotidine has been linked to heart-related issues, such as Long QT syndrome. This can cause a fast, pounding, or irregular heartbeat and may lead to fainting. If you have a history of heart rhythm problems, it is crucial to discuss this with your doctor before taking famotidine.

Hematological and Liver Issues

Serious effects on the blood and liver are rare but have been reported. These can include:

Thrombocytopenia: A condition characterized by a low blood platelet count, which can lead to easy bruising or bleeding.
Hepatitis and Liver Damage: While cases are rare, famotidine has been linked to elevated liver enzymes and, in some rare instances, inflammation of the liver (hepatitis).

Severe Allergic Reactions

Like any medication, famotidine can cause a severe allergic reaction, though this is rare. Signs of a serious reaction include:

Hives and rash
Swelling of the face, tongue, or throat
Difficulty breathing or swallowing

Immediate medical attention is required if these symptoms occur.

Long-Term Use and Associated Risks

Over-the-counter famotidine is only intended for short-term treatment of heartburn, typically for no more than 14 days consecutively. Prolonged use, even at prescription doses, requires regular medical supervision. Long-term use has been associated with potential risks, including:

Vitamin B12 Deficiency: Famotidine's acid-reducing properties can interfere with the body's absorption of vitamin B12 over an extended period, which can potentially lead to neurological problems or anemia.
Acid Rebound: After prolonged use, discontinuing the medication can cause a temporary increase in acid production, leading to a return of symptoms.

Famotidine vs. Proton Pump Inhibitors (PPIs)

Famotidine (an H2 blocker) and PPIs (like omeprazole) are both used to treat acid-related conditions. However, their mechanisms and long-term side effect profiles differ, making the choice dependent on the specific condition and patient health.


Feature	Famotidine (H2 Blocker)	PPIs (e.g., Omeprazole)
Mechanism	Blocks histamine receptors to reduce acid production.	Directly inhibits acid pumps for stronger acid suppression.
Onset	Works faster, within an hour.	Takes longer to reach full effect.
Long-Term Use	Rare risk of vitamin B12 deficiency; lower risk of other complications compared to PPIs.	Associated with higher risks of bone fractures, low magnesium levels, and kidney issues.
Risk in Kidney Disease	Requires dosage adjustment; higher risk of CNS effects with accumulation.	May not require dosage adjustment but long-term use can affect kidney function.
Short-Term Use	Very safe for most people for up to 14 days.	Generally safe for short-term use.

Drug Interactions

Famotidine can affect how other medications are absorbed by the body, as many drugs rely on stomach acid to be properly processed. It is important to inform your doctor of all medications, supplements, and vitamins you are taking. Examples of potential interactions include:

Certain Antifungals (e.g., Ketoconazole): Decreased absorption of the antifungal, making it less effective.
Some HIV and Cancer Drugs: Reduced effectiveness due to altered absorption.
Tizanidine (Zanaflex): Increased levels of tizanidine in the blood, raising the risk of side effects like low blood pressure.

When to See a Doctor

It is important to contact a healthcare provider if you experience any of the following while taking famotidine:

Symptoms that do not improve or worsen after two weeks of taking the medication.
Signs of gastrointestinal bleeding, such as black or tarry stools or vomiting blood.
Heartburn accompanied by chest/arm pain, sweating, or lightheadedness, as these can be signs of a heart attack.
Unexplained weight loss, persistent stomach pain, or painful swallowing.
Any signs of a severe allergic reaction or CNS effects mentioned above.

Conclusion: Safe Usage and Risk Awareness

Famotidine is a highly effective and generally safe medication for managing acid-related issues when used correctly. However, understanding the spectrum of potential health problems—from common minor annoyances to rare but serious complications—is essential. Most importantly, individuals with kidney disease, the elderly, and those on other medications should exercise extra caution and consult with a doctor. For over-the-counter use, sticking to the recommended 14-day limit is key, as long-term use should always be medically supervised. Always prioritize a discussion with your healthcare provider to ensure that famotidine is the safest and most effective option for your specific health needs.

For more detailed prescribing information, consult authoritative sources like MedlinePlus.

Frequently Asked Questions

Over-the-counter famotidine is intended for short-term use, and you should not take it for more than 14 consecutive days without consulting a healthcare provider. Prescription use may be longer, but requires medical supervision.

The most common and typically mild side effects of famotidine include headache, dizziness, constipation, and diarrhea.

Yes. Famotidine is partially cleared by the kidneys, so individuals with moderate to severe kidney disease may need a dosage adjustment. This is because a slower clearance can lead to higher drug levels and an increased risk of side effects, particularly affecting the central nervous system.

While rare, famotidine can potentially cause mental or mood changes, such as confusion, depression, agitation, and hallucinations, especially in the elderly or those with impaired kidney function.

Although uncommon, serious side effects can occur, including central nervous system effects (like seizures), heart rhythm problems (Long QT syndrome), low blood platelet count (thrombocytopenia), and severe allergic reactions.

For long-term use, famotidine is generally considered safer than PPIs (e.g., omeprazole), which have been linked to a higher risk of issues like bone fractures. However, long-term famotidine use may carry a risk of vitamin B12 deficiency.

If you experience any signs of a serious allergic reaction, such as swelling of the face or trouble breathing, or other severe symptoms like seizures, stop taking the medication and seek emergency medical help immediately.