Metronidazole Dosage Chart for Cats: Risks, Side Effects, Dosage, and More

Important Points

A combination antibiotic and antiparasitic drug, metronidazole is used to treat a number of ailments.

It is crucial to make sure your veterinarian is aware of all prescription and over-the-counter medications, vitamins, supplements, and herbal remedies you give your pet because this medication may interact with other prescriptions your cat may be receiving.

There is a chance that this medicine will cause serious, perhaps fatal adverse effects. Thus, a prescription and close supervision by a qualified veterinarian are necessary.

An antibiotic and antiparasitic drug called metronidazole is used to treat infections in dogs, cats, horses, and people. The Food and Drug Administration (FDA) in the United States has banned the use of this drug in animals that are raised for food, such as pigs and cows.

Research has demonstrated that chronic usage causes cancer in mice. Although there is some disagreement over metronidazole’s ability to cause cancer, there are other potential very harmful side effects. As such, it can only be used under the specific supervision of a veterinarian (or physician for humans).

We kindly remind everyone who is reading this page that administering any form of medication to your pet necessitates the guidance and advice of a veterinarian. Veterinarian advice is not replaced by this article. If you give your cat medication without first consulting a veterinarian, there could be serious negative effects, including death.

Together, let’s explore metronidazole’s benefits, drawbacks, dose, and other information for cats.

What is the purpose of metronidazole in cats?

There are various types of metronidazole. They consist of injections, tablets, liquid suspensions, and capsules. This medication is mostly used in the field of veterinary medicine to treat diarrhea. However, metronidazole is only used to treat a small number of particular conditions in cats by veterinarians. Veterinarians occasionally provide metronidazole for diarrhea without understanding why.

Since metronidazole is an antibiotic, it can be used to treat infections brought on by anaerobic bacteria, which do not need oxygen to survive. This drug is used in humans to treat some STDs, pelvic inflammatory disease, and dental abscesses. Metronidazole works as an antiparasitic, treating certain parasites that give cats diarrhea.


This illness, pronounced gee-ARE-dee-ay-sis, causes diarrhea. The pet becomes infected with Giardia duodenalis, also known as giardia, through fecal-to-mouth transmission of a minute parasite. Shared litter boxes and mutual cleaning are two ways that cats can spread it to one another. Giardia is very contagious because it can live for weeks or months on surfaces outside of the body. A zoonotic disease, giardiasis is present all over the world. This implies that it can spread from animals to people and vice versa. All it takes for the parasite to enter your mouth is contact with contaminated objects. Putting your hands on a sandwich after handling an ill animal, for instance.

Metronidazole is typically the first line of treatment if your cat has giardia. After handling contaminated animals and any surfaces they have come into contact with, it is crucial to wash your hands. Metronidazole-resistant giardia rarely develops. Veterinarians may alternatively recommend rodidazole in such circumstances.

Veterinarians use a fecal (poop) sample test to confirm giardiasis. While some are able to test for giardiasis internally, others need to submit the sample to a laboratory.


Similar to try-trick-o-MOAN-is, this fecal parasite is also typical in cats. This illness is brought on by an intestinal parasite that is peculiar to felines, called Tritrichomonas foetus (or tritrich for short). Thus, it cannot be transmitted from cats to humans. Cats do, however, definitely spread it to one another. This is particularly true for young cats that live in multi-cat homes or in huge populations (like feral colonies). Weight loss and severe diarrhea are the hallmarks of this illness.

One study examined the efficacy of various drugs in addition to metronidazole for treating cats with tritrich. The findings differed from those of other studies that the paper cited. Although metronidazole seems to be less successful than rovidazole, some cats need to be treated with various drugs over several rounds in order to eradicate the illness. Breeds include Abyssinian, Siamese, Bengal, and Norwegian Forrest Cat are more prone to tritrich, according to the same study.


This disease develops when an animal eats a lot of fat, which leads to the pancreas being extremely inflammatory. An essential organ shared by dogs, cats, and humans alike is the pancreas. It produces pain in the stomach region and bloody diarrhea when it gets inflamed. When a pet has pancreatitis, many of them stop eating and become frail from malnutrition and blood loss.

Hospitalization for pancreatitis is almost usually necessary in order to receive intravenous fluids—fluids that are injected straight into a vein—as well as intravenous metronidazole therapy. Medication is often given to cats to treat pain and nausea. There are cats who might need a nasogastric feeding tube. This is a little rubber tube that is inserted into the stomach through the throat and nose.

Depending on how severe the illness is, cats with pancreatitis have a fair to grave prognosis. A cat with a fair prognosis has a 50/50 chance of living and recovering, but a cat with a grave prognosis is more likely to die.

Side Effects of Metronidazole in Cats

In cats, metronidazole causes a few typical adverse effects. Still, more significant issues might arise. Below is a list of potential side effects along with more details about the most serious ones. Recall that the best course of action is to contact your veterinarian as soon as possible if you believe your cat is experiencing a side effect from any medicine!

Among the potential negative effects are:

Drooling/foaming at the mouth – due to the bitter taste and/or nausea
Refusal to eat –Cats can suffer from hepatic lipidosis (fatty liver syndrome) after only 48 hours without food.
Lethargy/lack of energy
Dark or bloody urine –this can be a sign of kidney failure
Vasculitis: This unusual side effect damages the skin’s outermost layer and produces inflammation. Hair loss, bruising, edema, and rash are among the symptoms.
Neurological issues: In cats, metronidazole adverse effects can be rather significant. Lack of coordination or control over muscles, tremors, seizures, vomiting, twitching of the eyes, and weakness are some of the symptoms.
Liver toxicity: Metronidazole can harm a cat’s liver. This condition is indicated by jaundice, which is a yellowing of the skin, whites of the eyes, and gums. It can typically be treated if detected early. On the other hand, the liver may shut down and cause mortality if treatment is delayed.

When Should Cats Not Take Metronidazole?

Metronidazole should not be used in pregnant or nursing Queens, especially in the first trimester, according to Dr. Shelly Wyatt, a licensed doctor of veterinary medicine at Northwood Hills Animal Hospital, who spoke to AZ Animals. Neither in infants nor in situations with significant hepatic or renal failure. When liver or kidney dysfunction is mild to moderate, it should be used with caution. Additionally, as it speeds up the drug’s metabolism, it should be avoided if the pet is taking phenobarbital. Because the liver and kidneys are still growing in newborns, injury and serious dysbiosis could happen.

Newborn kittens are called neonates. An imbalance of yeast and beneficial bacteria in the digestive tract is known as dysbiosis. These kittens are really delicate because they are still developing at such a young age. Any medicine could stunt their growth, causing serious issues that could even result in death.

Medications Your Cat Cannot Take With Metronidazole

In cats, metronidazole negative effects can be exacerbated by some medications. Therefore, before adding any new medications, it’s crucial to discuss all of your cat’s current prescriptions with your veterinarian. This also applies to vitamins, supplements, and over-the-counter medications. Let’s discuss a few drugs and the problems they may create when taken with metronidazole in cats.

Cimetidine: This drug relieves acid reflux and stomach ulcers. It can prolong the time it takes for metronidazole to leave the body when used with it in cats. We refer to this process as drug metabolism. Excessive or insufficient medication metabolism might lead to serious adverse effects.

Phenobarbital –
The seizure-prevention drug phenobarbital causes cats’ metabolism of metronidazole to increase. In other words, it speeds up the body’s metabolism of metronidazole. This can raise the likelihood of adverse effects or render the metronidazole ineffective.

On the other hand, cyclosporine is more metabolically active in cats when metronidazole is administered. This raises the possibility of cyclosporine adverse effects.

Metronidazole can potentially have an impact on phenytoin, an anti-seizure medication, in cats. Metronidazole decreases phenytoin metabolism, although the opposite is also true. In other words, phenytoin speeds up the body’s metronidazole processing. These consequences may increase the chance of phenytoin adverse effects and prevent metronidazole from working. Stumbling, weakness, tiredness, and low platelet counts (which can cause internal bleeding) are among the side effects of phenytoin.

Cats are hardly ever prescribed this anticoagulant (drugs that stop blood clots). In the event of cuts, scratches, and other wounds, however, combining with metronidazole can raise the risk of internal bleeding and inhibit blood coagulation.

Causes of Your Cat’s Inability to Take Metronidazole

Dr. Wyatt mentioned that she is less able to give cats metronidazole in a number of circumstances. They are listed below. This is by no means an exhaustive list. Again, before giving your cat metronidazole, always consult your veterinarian.

During pregnancy, metronidazole can harm unborn kittens by making its way into the uterus, where kittens thrive. This could lead to potentially fatal birth abnormalities.

Nursing Mothers: Since the medicine can contaminate the milk, it should also be avoided in cats who are nursing kittens.

Less than six weeks old: While age alone does not indicate a medical issue, it can occasionally make it impossible to take certain medications. As Dr. Wyatt mentioned, treating newborn kittens metronidazole can seriously harm their kidneys and liver.

Liver or Kidney illness: Cats who already suffer from liver or kidney illness may find it difficult to effectively absorb metronidazole. Some of the more severe adverse effects we’ve talked about could result from this.

Final Thoughts on Metronidazole for Cats

As usual, owners ought to consult their veterinarian before administering any medication to their cat. When used appropriately, metronidazole is a helpful medication for conditions like feline giardiasis. Even at the prescribed dosage, metronidazole can be extremely hazardous to cats. If you must give your cat metronidazole, make sure to wash your hands afterward. Additionally, keep a watchful eye out for any indications of adverse effects and contact your veterinarian immediately if you do.

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Dosage Chart for Metronidazole in Cats

Unless directed otherwise, always adhere to your veterinarian’s instructions to the letter and complete the recommended course of treatment, even if your cat seems to be feeling 100% better.

For cats, the usual dosage of metronidazole is 16–55 mg/pound every 12 hours, or twice a day. This greatly depends on the ailment that has to be treated. Excessive use of 55 milligrams per pound may cause severe adverse effects. This chart is intended solely for informational reasons. Give your cat metronidazole only after speaking with a veterinarian.

Cat’s Weight in Pounds Metronidazole Dosage Cat Breeds Include
0-5 16-275 mg per dose Singapura, Bambino
6-10 96-550 mg per dose Siamese, Cornish Rex
11-20 176-1,100 mg per dose Bengal, Ragdoll
Over 20 consult your vet Maine Coon, Savannah