Metronidazole for Cats: Uses, Dosage & Side Effects

This information is for educational purposes only. Never give your pet any medication without your veterinarian's guidance. Dosing, frequency, and safety depend on your pet's specific health profile.

Metronidazole is a prescription medication in the nitroimidazole family. Your vet may use it in cats for certain anaerobic bacterial infections and some protozoal infections, especially when diarrhea or large-bowel inflammation is part of the problem.

In veterinary medicine, metronidazole is also sometimes used for its anti-inflammatory effects in the digestive tract. That means your vet may prescribe it not only to target infection, but also as part of a broader plan for colitis or chronic intestinal disease.

This medication is not FDA-approved for cats in the United States, so feline use is extra-label under veterinary supervision. That is common in veterinary medicine, but it makes accurate dosing and follow-up especially important.

Metronidazole has a very bitter taste, which can make tablets hard for some cats to take. If pilling is stressful, your vet may recommend a compounded liquid or capsule that is easier to give.

Your vet may prescribe metronidazole for cats with Giardia, some other protozoal infections, or infections caused by anaerobic bacteria. These bacteria tend to thrive where oxygen is low, such as deep wounds, abscesses, dental infections, or parts of the intestinal tract.

It is also used in some cats with colitis, chronic diarrhea, or inflammatory bowel disease, although it is not always the only treatment. In many cases, your vet pairs it with diet changes, probiotics, deworming, fecal testing, or another medication based on the likely cause.

Metronidazole is not the right choice for every cat with diarrhea. Vomiting, diarrhea, and appetite changes can come from parasites, food sensitivity, pancreatitis, toxin exposure, liver disease, or other conditions that need different care.

Because of that, the best use of metronidazole starts with a diagnosis plan. A fecal test, exam, and sometimes bloodwork help your vet decide whether this medication fits your cat's situation.

Always give metronidazole exactly as your vet prescribes. Do not calculate a dose from internet examples or from another pet's prescription. In cats, the dose depends on the reason for treatment, body weight, liver function, and how long the medication is expected to be used.

Published veterinary references list indication-specific oral doses for dogs and cats, including 25 mg/kg every 12 hours for 5 days for giardiasis, 10-15 mg/kg every 12 hours for some inflammatory GI conditions, and 7.5 mg/kg every 8-12 hours for hepatic encephalopathy. Cats with liver dysfunction may need lower or less frequent dosing because metronidazole is processed primarily by the liver.

Many vets prefer to stay on the lower end of the dosing range in cats, especially for longer courses, because neurologic side effects become more likely with higher doses or prolonged use. If your cat misses a dose, ask your vet or pharmacist what to do. In general, do not double the next dose unless your vet specifically tells you to.

Giving the medication with a small amount of food may help reduce stomach upset, but follow the label directions from your vet or pharmacy. If your cat drools heavily after dosing, the bitter taste may be the cause, and your vet may be able to offer a different formulation.

Many cats tolerate metronidazole reasonably well, but side effects can happen. Mild problems may include drooling, reduced appetite, nausea, vomiting, or diarrhea. Because the medication tastes very bitter, some cats foam or salivate right after a dose even when the drug itself is not causing a true reaction.

The most important side effects to watch for are neurologic signs. These can include wobbliness, stumbling, head tilt, unusual eye movements, tremors, weakness, disorientation, or seizures. These reactions are more likely with higher doses, longer treatment courses, or in pets with reduced liver function.

Less common but more serious concerns include yellowing of the eyes or gums, marked lethargy, or signs that your cat is getting worse instead of better. Rare blood-related side effects have also been reported in animals.

If you notice neurologic changes, severe vomiting, collapse, or yellowing of the skin or eyes, see your vet immediately. Do not keep giving the medication until you have spoken with your vet.

Metronidazole can interact with other medications, supplements, and compounded products. Two interactions specifically highlighted in veterinary references are cimetidine, which can slow metronidazole metabolism and raise exposure, and phenobarbital, which can increase metabolism and reduce drug levels.

Because metronidazole is processed in the liver, your vet should also know if your cat takes other drugs that affect liver enzymes or have neurologic side effects. This is especially important in senior cats and in cats with liver disease.

Tell your vet about every medication and supplement your cat receives, including probiotics, antacids, appetite stimulants, seizure medications, pain medications, and any human products. Even if an interaction is not absolute, it may change the safest dose or monitoring plan.

If your cat has had a prior reaction to metronidazole or a related drug such as ronidazole, mention that before treatment starts. That history can change whether your vet chooses this medication at all.