Why does my cat's breath smell like fish?

If you notice persistent cat bad breath that smells like fish, check the food bowl first and consider switching to a non-seafood protein if they’ve been eating a fish-based diet. Remember to consult with your veterinarian about the best food swap, and be sure to wash bowls regularly. Keep in mind that fishy scents are normal after some meals, but they should fade quickly. If the smell sticks around or your cat seems uncomfortable, it’s time to visit the veterinarian to check for dental issues or underlying health concerns.

Can changing my cat's diet fix bad breath?

While changing your cat’s diet can help with tummy issues, it rarely fixes the bad breath brought on by dental disease. That said, some crunchy dental treats (or specialized dental diets) can help scrub away the plaque and tartar that causes bad breath. Look for treats with the VOHC seal for the best results. Try the treats first, and then check with your veterinarian about switching food. This will ensure that your cat gets the nutrients they need for a healthy, fresh smile.

Does teething cause bad breath in kittens?

Yes, teething can cause temporary bad breath in kittens (typically between three and six months old). Once their permanent teeth are in, the bad breath should clear up. If it doesn’t, visit your veterinarian. They’ll be able to help identify the cause of the foul odor.

Cat Bad Breath: Symptoms, Causes and Treatment

Published February 10, 2026

Reviewed by Jessica Gilliam, DVM

If your cat’s breath is bad, it might mean they need a little extra care for their dental health. While many owners expect a slight “tuna smell” after their feline friend eats canned food, a really bad odor is usually a red flag.

The smell is often caused by dental issues, but persistent odors can sometimes be a warning sign of deeper health issues, including kidney disease.

By establishing a daily cleaning routine and visiting a veterinarian for regular checkups, you can address problems before your cat experiences pain, tooth loss, or more serious conditions.

In this guide, we’ll break down the most common causes of cat bad breath and how to spot the warning signs. We’ll also look at the best treatment options and simple steps you can take at home to keep your cat’s mouth healthy and fresh.

Key Takeaways

The most common cause of cat bad breath is plaque and tartar buildup which can lead to periodontal disease and create a sulfur-like odor.
Other common causes of cat bad breath include kidney disease (ammonia smell), diabetes (sweet smell), liver disease, and foreign objects stuck in their mouth.
Treatment for bad breath in cats includes veterinary oral exams, professional cleaning under anesthesia, and treatment for underlying conditions.
To prevent bad breath, brush your cat’s teeth every day, give them dental treats, and get them in for an annual veterinary dental exam.

What Is Bad Breath in Cats?

A healthy cat’s breath shouldn’t smell bad. If it does, they might have halitosis, the medical term for chronic bad breath.

Halitosis can indicate other, more serious issues, such as periodontal disease and underlying health conditions, which we’ll discuss in more detail in the next section.

Surprisingly, most cats show signs of dental disease by age three, and the risk increases with age, poor dental care, and genetics. This is why regular checkups and dental treats are essential for keeping your cat’s smile healthy and their breath fresh.

But why does your cat’s breath start smelling bad in the first place? Is it always a serious concern? To answer those questions, let’s take a closer look at possible causes of your cat’s bad breath.

What Causes Your Cat’s Bad Breath?

Cat bad breath can be caused by many things. To help you narrow down the possibilities, here are the most common causes.

Periodontal Disease

When plaque and tartar build up on your cat’s teeth, it can lead to periodontal disease. If this happens, the bacteria in their mouth can cause infections and tooth decay.

Once your cat’s teeth decay, you’ll notice a sulfur-like smell that might remind you of rotten eggs. If left untreated, the bacteria can enter your cat’s bloodstream and cause even more serious health problems.

Fortunately, you can care for your cat’s oral health with GREENIES™ Cat Dental Treats. Their crunchy texture, delicious taste, and quality ingredients can help keep your cat’s teeth clean to reduce plaque buildup (and bad breath!).

Gastrointestinal Problems

Bad breath could also be a sign that your cat is having tummy troubles. In addition to the odor, you’ll likely notice other symptoms, such as vomiting, diarrhea, drooling, and changes in behavior.

Many factors can lead to gastrointestinal distress, including hairballs, eating non-edible objects, and food allergies.

Underlying Health Conditions

Some underlying health problems can cause bad breath. These include:

Kidney disease: Produces an ammonia- or urine-like smell in the mouth as waste products build up in the blood and get released through the breath.

Diabetes: Causes sweet or fruity-smelling breath, which indicates a serious condition called ketoacidosis.

Liver disease: Results in foul or musty odor that may be accompanied by vomiting.
Oral cancer or tumors: Can cause persistent bad breath with visible sores or masses in the mouth.
Respiratory infections: May produce foul breath along with sneezing or nasal discharge.

Eating Something Smelly

If your cat has been scavenging around in the garbage or eating something dead, it could make their breath temporarily foul. If you’ve seen your kitty getting into mischief and then smell something, wait a day or two to see if the smell goes away. You’ll also want to watch for stomach upset.

At that point, if the smell is gone, you can chalk it up to their curious nature. However, if it lingers, there’s likely something else going on.

When to See Your Veterinarian

Not all cat bad breath requires an emergency visit, but if it’s accompanied by certain symptoms, you may need to see your veterinarian as soon as possible. Let’s take a look at when emergency care is needed versus a routine checkup.

A Routine Appointment

Catching bad cat breath early is the best way to keep your feline friend purring. If their bad breath persists for more than a few days or if you spot yellow or brown buildup on their teeth and redness along their gumline, it’s time for a checkup.

Regular dental care keeps their mouth fresh and prevents small issues from becoming big, painful problems later on.

Prompt Veterinary Care

Sometimes, a serious change in scent is a serious red flag. If your cat’s breath smells sweet like fruit or smells sharp like ammonia, call your veterinarian immediately.

These odors, along with drooling, bleeding, or a loss of appetite, often signal deeper health concerns, such as kidney disease and diabetes. Prompt action ensures that your cat gets the care they need to stay happy, healthy, and active.

Treating and Preventing Bad Cat Breath

While you may not be able to prevent every occurrence of bad breath in your cat, the following steps can help keep things fresh.

Establish a Home Oral Care Routine

Like humans, cats need regular oral care. A simple at-home routine can help keep their mouth healthy and their breath fresh.

Purchase a finger toothbrush or a soft toothbrush specially designed for felines, along with cat toothpaste or gel (which often comes in cat-friendly flavors like poultry and fish). It’s important to note that the ingredients in human toothpaste can harm your pet, so don’t try to share your tube.

Once you have everything you need, don’t make the mistake of putting some cat toothpaste on the brush and diving in for a vigorous cleaning. Doing so can scare your kitty and make them resistant to any future attempts.

Instead, learn how to brush your cat’s teeth correctly. Let’s get into it.

How to Brush Your Cat's Teeth

Start by letting your cat lick toothpaste off your finger for a couple of days, and monitor their stool and appetite when trying something new. Once they’re comfortable with the toothpaste, gently rub some along their outer gumline with your finger for a few more days.

Next, introduce the toothbrush by touching it to their mouth briefly. Then you can start (gently) brushing their teeth. Gradually increase brushing time as your cat adjusts to the process.

When you finish, reward your cat with praise and a dental treat so they associate the process with love and yummy food.

Here are some more tips for success when brushing your cat’s teeth:

Aim for daily brushing, but even a few times per week helps

Only brush the outer surfaces of teeth where plaque builds up

Keep sessions short and stress-free
If your cat resists, take a break and try again later

Use GREENIES™ Dental Cat Treats

If you’re looking for an easier way to keep plaque and tartar at bay, give your cat a few GREENIES™ Cat Dental Treats & Chews twice a day. These treats are made from natural ingredients and come in flavors cats love, like oven-roasted chicken and salmon.

Our treats have a crunchy texture to help clean your cat’s teeth. They’re designed to reduce tartar buildup and keep your kitty’s breath smelling nice.

Since each treat has only two calories, you can feel good about giving them to your cat. Feel free to use them as a reward or pop a few into their regular kitty chow! (Just remember that treats should make up no more than 10% of your pet’s daily calories.)

Schedule a Dental Exam

As helpful as home care is, it can’t replace professional cleanings. Get your cat to the veterinarian for a dental checkup and cleaning at least once a year. This can help ensure any oral problems are caught early, before they lead to bad breath or other trouble.

Feed Your Cat Quality Food

If your kitty frequently deals with bad breath and gastrointestinal issues, a diet change might be worthwhile. Your veterinarian can help you find the best brand for your cat, but you’ll likely want to look for a formula high in animal protein and low in carbs.

The type of food is also important. Some veterinarians think dry kibble is better for your cat’s teeth since it can help remove plaque. However, the studies aren’t yet conclusive on this topic, so if your cat prefers wet food, it’s OK to offer that as long as your veterinarian approves.

Common Myths About Cat Bad Breath

Bad Breath Is Normal in Cats

A constant foul odor isn't normal, even for cats. While a little fishy scent after dinner is fine, a constant foul odor is not. If stinky breath lingers, it’s usually a sign of a hidden health issue that needs your attention right away.

Any Dry Food Diet Cleans Cats’ Teeth

Think the dry food your cat eats every day will keep their teeth clean? Maybe, but not always.

Some dry cat food breaks apart too quickly to actually scrub away the plaque and tartar that can cause bad breath. The kibble’s effectiveness also depends on how your cat eats. If they gulp the kibble down, it won’t benefit their dental health.

For the best chance of getting your cat’s teeth clean while they eat, look for a specialized dental diet with the Veterinary Oral Health Council (VOHC) seal of approval. This kibble is designed to resist crumbling and act like a tiny toothbrush to gently scrub your cat’s teeth while they eat.

Cats Don't Need Dental Care

It’s a common myth that cats are maintenance-free and don’t need dental care. Most felines show dental disease by age three, so, without daily brushing and yearly veterinarian visits, your cat could face serious pain or tooth loss.

Cats are also great at hiding pain and discomfort, so veterinary visits are needed to help identify any potential problems. What’s more, taking care of their teeth now prevents deeper health issues later and keeps your feline friend’s smile bright and their body feeling great for years to come.

Bad Breath Will Go Away on Its Own

Waiting for cat bad breath to go away on its own rarely works. Yes, the smell after a tuna meal may fade fast, but a persistent odor will usually only get worse without treatment. Early intervention is the secret to fresh breath!

Improve Your Cat’s Breath With GREENIES™

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If your cat has bad breath, it may indicate an underlying problem. That’s why regular oral exams are so important. After inspecting your cat’s mouth, the veterinarian can pinpoint the cause of the odor and recommend personalized treatment options.

Between visits, keep your cat’s breath fresh by brushing their teeth and giving them GREENIES™ Cat Dental Treats daily. These treats are formulated to reduce tartar buildup. Plus, they contain essential nutrients that can help keep your bundle of fur healthy.

To keep your cat coming back for more, stock up on a variety of GREENIES™ treats. Try different flavors, like tuna and catnip, to keep your feline friend purring in delight!

Contributor

Jessica Gilliam is a veterinarian with more than 14 years of clinical experience, specializing in small animal medicine. She is passionate about surgery, dentistry, mentorship, and education. Jessica serves as the Community Chair for the Tennessee Market at Banfield and oversees Mars Petcare’s PetConnect chat, which offers free educational support for pet parents. In her free time, she enjoys hiking and baking.

References

Frequently Asked Questions

All Questions cat bad breath

Why does my cat's breath smell like fish?

If you notice persistent cat bad breath that smells like fish, check the food bowl first and consider switching to a non-seafood protein if they’ve been eating a fish-based diet. Remember to consult with your veterinarian about the best food swap, and be sure to wash bowls regularly.

Keep in mind that fishy scents are normal after some meals, but they should fade quickly. If the smell sticks around or your cat seems uncomfortable, it’s time to visit the veterinarian to check for dental issues or underlying health concerns.
Can changing my cat's diet fix bad breath?

While changing your cat’s diet can help with tummy issues, it rarely fixes the bad breath brought on by dental disease.

That said, some crunchy dental treats (or specialized dental diets) can help scrub away the plaque and tartar that causes bad breath. Look for treats with the VOHC seal for the best results.

Try the treats first, and then check with your veterinarian about switching food. This will ensure that your cat gets the nutrients they need for a healthy, fresh smile.
Does teething cause bad breath in kittens?

Yes, teething can cause temporary bad breath in kittens (typically between three and six months old). Once their permanent teeth are in, the bad breath should clear up. If it doesn’t, visit your veterinarian. They’ll be able to help identify the cause of the foul odor.

Cat Bad Breath: Symptoms, Causes and Treatment

Key Takeaways

What Is Bad Breath in Cats?