What happens if you give a dog too much famotidine?

October 11, 2025 •

4 min read

While famotidine (brand name Pepcid) has a wide safety margin in dogs, overdoses are still possible and require immediate attention. Knowing what happens if you give a dog too much famotidine is crucial for any pet owner, as the severity of symptoms depends on the amount ingested.

Quick Summary

Accidental ingestion of excessive famotidine by a dog can lead to symptoms ranging from mild gastrointestinal upset to more severe cardiovascular and neurological issues. Owners should recognize overdose signs, follow immediate emergency protocols, and seek veterinary treatment promptly to ensure the best outcome.

Key Points

Wide Safety Margin: Famotidine has a broad safety range in dogs, and severe toxicity is unlikely unless an extremely large number of pills are ingested.
Recognize Overdose Symptoms: Symptoms can range from mild issues like vomiting and diarrhea to severe signs including heart rate changes, low blood pressure, and collapse.
Contact a Professional Immediately: In case of a suspected overdose, contact a veterinarian or a pet poison control center for expert guidance.
Decontamination and Supportive Care: Veterinary treatment may involve inducing vomiting, administering activated charcoal, and providing supportive care with IV fluids.
Prevent Accidental Overdose: Keep all medications secured and out of your pet's reach and always follow your vet's prescribed dosage instructions precisely.
Distinguish from Mild Side Effects: Not all reactions are overdoses; some mild side effects like transient lethargy or diarrhea are possible even at the correct dose.

Understanding Famotidine and its Use in Dogs

Famotidine is a histamine-2 (H2) receptor antagonist, which works by reducing the amount of stomach acid produced. In veterinary medicine, it is a commonly prescribed medication to treat and prevent gastrointestinal issues in dogs, such as stomach ulcers, gastritis, and acid reflux. While available over-the-counter for humans, pet owners should only administer famotidine to their dogs under the specific guidance and dosage instructions of a veterinarian. The proper dose for a dog is typically based on its body weight, with standard recommendations ranging from 0.5 to 1 mg per kilogram.

The Wide Safety Margin and Overdose Risks

It is reassuring to know that famotidine is considered to have a wide margin of safety for dogs. In fact, research studies have shown that dogs can tolerate very high doses with minimal side effects. A lethal overdose is highly unlikely from a few extra tablets, and would typically require a dog to ingest a massive quantity, such as hundreds of pills. However, this wide safety margin does not mean owners should be complacent, as moderate to large overdoses can still cause concerning symptoms. Overdoses often occur accidentally, such as when a dog gets into a bottle of human-grade medication stored improperly. The potential for adverse effects is also higher in dogs with pre-existing conditions like kidney, liver, or heart disease.

Mild to Moderate Overdose Symptoms

If your dog has ingested a higher-than-prescribed dose of famotidine, you may observe several signs of gastrointestinal upset and general malaise. These are typically mild but should still be taken seriously.

Vomiting
Diarrhea
Pale gums
Loss of appetite
Drowsiness or lethargy
Restlessness
Excessive drooling

Severe Overdose Symptoms

In cases where a very large quantity of famotidine has been ingested, the symptoms can become more severe and life-threatening, potentially affecting the cardiovascular system. These symptoms constitute a veterinary emergency.

Low blood pressure (hypotension)
High or irregular heart rate (tachycardia)
Difficulty breathing
Disorientation or confusion
Stumbling or loss of coordination
Collapse

What to Do If Your Dog Has Ingested Too Much Famotidine

If you suspect your dog has received an overdose of famotidine, your immediate and calm response is vital. Do not wait for severe symptoms to appear. The following steps should be taken immediately:

Assess the situation: Determine how much famotidine your dog ingested and when it happened. Gather the medication bottle or packaging for reference. Do not induce vomiting unless specifically instructed by a veterinarian or a poison control expert.
Contact a professional: Call your veterinarian, a 24-hour emergency animal hospital, or a pet poison control helpline immediately. Poison control hotlines, such as the ASPCA Animal Poison Control Center or Pet Poison HELPLINE, are staffed by experts who can provide guidance.
Follow all instructions: The professional you speak with will advise you on the next course of action based on the amount ingested and your dog's size and health. They may recommend monitoring your dog at home or bringing them in for immediate care.
Do not use internet remedies: Never rely on unverified online advice for a medical emergency. Stick to the recommendations of a veterinary professional.

Veterinary Treatment for Famotidine Overdose

When a dog is brought to a veterinary clinic for a famotidine overdose, the treatment will be tailored to the severity of the case and how recently the ingestion occurred.

Decontamination: If the ingestion was recent, the vet may induce vomiting to remove the medication from the stomach. Activated charcoal might also be administered to bind any remaining drug in the stomach and prevent its absorption.
Supportive care: For more severe cases, supportive therapy will be necessary. This may involve intravenous (IV) fluids to support blood pressure and counteract dehydration from vomiting and diarrhea.
Monitoring: The vet will monitor the dog's vital signs, including heart rate and blood pressure, to ensure they remain stable. They will continue to observe the dog until they are stable and all signs of overdose have passed.

Famotidine Overdose vs. Mild Side Effects: A Comparison

It is important for pet owners to distinguish between a regular, mild side effect and a more serious overdose reaction. Below is a comparison to help clarify the differences.


Characteristic	Mild Side Effect	Overdose Reaction
Symptom Severity	Generally mild and infrequent.	More severe, frequent, or rapidly escalating.
Gastrointestinal	Slight diarrhea, occasional vomiting.	Persistent or bloody vomiting, severe diarrhea.
Appetite	Can be decreased or lost temporarily.	Complete refusal to eat.
Energy Level	May show mild lethargy or fatigue.	Significant weakness, drowsiness, or collapse.
Cardiovascular	Typically unaffected.	High or irregular heart rate, low blood pressure.
Neurological	May cause mild restlessness.	Disorientation, uncoordinated movements.

The Crucial Role of Prevention

Preventing a famotidine overdose is far easier and safer than dealing with the aftermath. Owners should always follow these crucial preventative measures:

Secure Storage: Always keep all medications, including over-the-counter products, out of your dog's reach. Use child-proof locks on cabinets or store medications on high shelves.
Follow Dosage Directions: Only give the exact dose prescribed by your veterinarian. Never give a double dose to make up for a missed one.
Avoid Self-Medicating: Do not give your dog human famotidine without consulting a vet first. Always confirm the correct dosage and formulation, as some human products contain other ingredients that are toxic to dogs.

Conclusion

While famotidine is a generally safe and effective medication for treating gastric issues in dogs, the risk of an overdose should not be taken lightly. Understanding what happens if you give a dog too much famotidine involves recognizing the distinction between mild side effects and severe overdose symptoms. In a suspected overdose, the priority is to contact a veterinary professional immediately for guidance. Proper medication storage and strict adherence to veterinary instructions are the most effective ways to prevent accidental overdoses and ensure your dog's safety and well-being. For more detailed information on common drug interactions and safety, consult the Merck Veterinary Manual.

Frequently Asked Questions

While the toxic dose is very high, any amount over the dose prescribed by your veterinarian is considered an overdose. Symptoms of a moderate overdose can appear after ingesting more than the recommended amount, so contacting a vet is always the safest course of action.

Early signs of a famotidine overdose often include gastrointestinal issues like vomiting, diarrhea, loss of appetite, and pale gums. The dog may also seem drowsy or unusually restless.

A fatal overdose is possible but highly unlikely with oral ingestion, as it would require the dog to consume an extremely large number of tablets. However, severe complications can occur from large overdoses, which is why immediate veterinary attention is critical.

If your dog ingests a double dose, you should immediately contact your veterinarian or a pet poison control helpline for advice. They will help you assess the risk based on the dog's weight and the amount ingested and determine if treatment or monitoring is needed.

Human famotidine is often prescribed by vets for dogs, but you should never administer it without your vet's specific instructions. It is important to confirm the correct dosage and ensure the product does not contain any other ingredients harmful to dogs.

Depending on how much time has passed since ingestion, a vet might induce vomiting or administer activated charcoal to limit absorption. Supportive care, including IV fluids and vital signs monitoring, may also be used for more severe cases.

Long-term use should be monitored by a veterinarian, especially for dogs with pre-existing conditions like kidney, liver, or heart disease. Some vets suggest that famotidine's efficacy may decrease over time, and alternatives may be considered.