I Gave My Cat Too Much Dewormer (What Should I Do?)

dewormer overdose symptoms in cat

Accidentally giving your cat too much dewormer can be alarming. Many of these dewomers can become toxic when ingested in higher doses.

Dewormers are crucial for eliminating parasites in cats, but overdosing can lead to symptoms like vomiting and lethargy. If an overdose occurs, immediately contact a vet or poison control, and avoid home remedies. Always double-check dosages, especially for kittens, to prevent overdose risks.

This post tackles the crucial steps to take if you find yourself in this situation, focusing on recognizing dewormer overdose symptoms in cats.

What Are Deworming Medications Used For?

Deworming is essential for eliminating internal parasites that can harm your pets.

There are various forms of dewormers, including pills, liquids and topicals, each suited for different types of worms.

Dewormers are used to get rid of feline parasites such as:

  • Hookworms
  • Tapeworms
  • Heartworms
  • Roundworms
  • Whipworms

What makes dewormers so effective is due to the active ingredients used to eliminate these parasites.

The most common active ingredients are:

  • Pyrantel Pamoate
  • Ivermectin
  • Piperazine
  • Fenbendazole
  • Praziquantel
  • Milbemycin oxime
  • Moxidectin (Topical) 
  • Selamectin (Topical)

Dewormers are made of a combination of two of the above-mentioned active ingredients, which gives them a broader spectrum against different parasites.

Some (like selamectin) are active against both internal and external parasites.

Dewormer Overdose Symptoms In Cats


Vomiting is a common and early symptom of dewormer overdose in cats. This reaction occurs as the body’s immediate response to expel the toxic substance ingested.

Your cat might be meowing before it throws up due to the discomfort it is feeling.

Vomiting can lead to dehydration and other adverse side effects if it becomes frequent. This makes it critical to monitor your cat’s hydration levels.


Diarrhea, similar to vomiting, is the cat’s body’s way of eliminating toxins.

Loose, watery stools can quickly lead to dehydration and electrolyte imbalance. If diarrhea persists, it can start to take a toll on your cat’s body very quickly.

Excessive Salivation

Excessive salivation or drooling can indicate nausea or discomfort from an overdose of dewormers.

Persistent drooling, while not as serious as other symptoms, still needs to be checked by a vet to rule out serious issues.

Tremors Or Seizures

Tremors or seizures in cats following a dewormer overdose are very concerning. This means that the cat’s nervous system has been impacted by the active ingredients in the dewormer.

Ingredients like ivermectin can cross the blood-brain barrier in high doses, interfering with the central nervous system’s function.

Ivermectin toxicity can lead to severe neurological symptoms, including tremors and seizures.

This is a sign of acute toxicity in cats.

These symptoms require urgent veterinary attention to prevent long-term damage or life-threatening conditions such as respiratory failure or coma.

Treatment may involve medication to control seizures and supportive care to detoxify the body.

Lethargy Or Weakness

When your cat shows lethargy or weakness after receiving too much dewormer, it’s a sign that its body is actively trying to neutralize the overdose.

The body uses a lot of energy fighting the overdose and this results in lethargy. This effort can significantly drain the cat’s energy and affect its normal behavior.

Loss Of Appetite

Loss of appetite in cats after dewormer overdose is concerning as it reflects the body’s adverse reaction to the medication.

This lack of desire to eat may be caused from:

  • Nausea
  • Abdominal discomfort
  • Systemic reaction

Do note that some cats can suffer from a loss of appetite from normal doses of dewormers. But it spontaneously resolves after a day or two.

But if your cat’s lack of appetite persists for more than 48 hours, you should take it to the vet for a check-up.

Ignoring this symptom can weaken the cat’s ability to recover fully.

What To Do If I Overdosed My Cat?

cat at vet

If you suspect a dewormer overdose in your cat, immediately contact emergency services or the ASPCA Animal Poison Control Center hotline.

It’s important to not attempt to treat an overdose at home without professional advice.

Let the vet or helpline know your cat’s age, weight, brand of dewormer and how much it has taken by mistake.

This will enable the medical professional to decide if your cat needs immediate medical treatment or to be closely monitored at home first for adverse reactions.

You might be tempted to induce vomiting in your cat but it can do more harm than good if done incorrectly.

Treatments at the vet may include inducing vomiting to remove the unabsorbed medication, administering activated charcoal to absorb toxins and providing supportive care like fluids and rest.

Take More Precaution When Deworming Kittens

When addressing dewormer overdose in kittens, it’s crucial to consider their smaller size and the need for accurate dosing.

Kittens are at higher risk of experiencing adverse reactions from an overdose due to their smaller and developing bodies.

There was a study that tested the efficacy of Pyrantel Pamoate on cats. The kittens in the study were given a high dosage of pyrantel pamoate at the rate of 100 mg/kg for three consecutive days.

This was 5x more the dosage given to another group of cats.

But thankfully, the kittens showed no adverse effects.

This doesn’t mean that it is still safe for a kitten to overdose on dewormers.

There’s no way of knowing how your little kitten will react to an abnormal amount of the active ingredient in the dewormer.

How To Prevent Dewormer Overdose At Home?

To prevent an overdose at home, always check the dosage carefully and keep a record of when you give medicine.

Visit the vet to get the right dewormer plan for your cat.

If you have more than one cat, make sure to keep their medicines separate so you don’t mix them up.

For topical dewormers, apply them to a part of your cat’s body they can’t lick, such as between the shoulder blades.

This prevents accidental ingestion and subsequent side effects like drooling or vomiting.

Never mix topical treatments in food or administer them orally as these are meant for external use only.

Do Cats React To Dewormers Even In Correct Doses?

Sometimes, even when given the right amount, a cat might not react well to dewormers. This is rare and can happen because each cat is different and younger cats are usually more sensitive.

They might feel very tired, drool more than usual, have trouble moving properly, or show signs like shaking.

They might also vomit or have diarrhea, similar to if they had too much dewormer.

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