Last Updated: 20/08/2026
Cat Bad Breath: Causes, Red Flags and What to Do at Home
Why does your cat's breath smell? Read our Vet-guide to the causes of cat bad breath, red flags to watch for, and what to do at home.
Author: Dr Gillian Hill BVSc (Hons)
Reading Time: 5 minutes - short read
If your cat's breath has gone from a bit fishy to properly stinky, you're not alone in noticing it. Cat bad breath (the vet term is halitosis) is really common, but it's not something to just live with. In most cases it's telling you something about what's going on in your cat's mouth, and sometimes it's a sign of something bigger. Here's what causes it, when it's worth a vet visit, and what you can do about it at home.
What causes bad breath in cats?
Dental disease
This is by far the most common cause of cat bad breath. Plaque builds up on the teeth every day, and if it isn't removed it hardens into tartar within days. Tartar creeps under the gumline and causes gingivitis (inflamed, often red or bleeding gums), which can progress to periodontal disease. The bacteria involved produce smelly sulphur compounds, which is where that unmistakable "fishy" or "off" smell comes from. Dental disease is extremely common in cats, and the risk climbs with age if teeth aren't cared for.
Other medical causes
Bad breath isn't always about the teeth. A few other things can be behind it:
- Kidney disease. When the kidneys aren't filtering properly, waste products build up in the blood and can make breath smell like ammonia or urine.
- Diabetes. Uncontrolled diabetes can cause a sweet or acetone-like smell on the breath, from ketones building up in the body.
- Oral tumours. Growths in the mouth can become infected or start to break down tissue, causing a strong, unpleasant smell. These are more common in older cats.
- Something stuck in the teeth. Hair, string or a bit of food wedged between the teeth or gums can cause localised infection and a nasty smell.
- Gut and respiratory issues. Tummy upsets or nasal and sinus infections can also change the smell of your cat's breath.
Diet-related causes
What your cat eats can play a role too. Wet food is more likely to stick to the teeth and gumline than dry food, giving bacteria something to feed on. Fishy flavoured foods can also leave a lingering smell of their own, which is worth ruling out before assuming it's dental disease.
Red flags: When to see the vet
A little "cat breath" is normal. But book a vet visit if you notice any of the following:
- Strong, pungent odour
- Drooling more than usual
- Pawing at the mouth or face
- Reluctance to eat, or eating on one side of the mouth
- Bleeding or very red, swollen gums
- Weight loss
- Lethargy or general off-colour behaviour
Sudden or severe changes are always worth getting checked, especially in senior cats, since bad breath can occasionally point to something more serious than dental disease alone.
What you can do about it at home
Brush your cat's teeth
Daily brushing is the gold standard for preventing plaque buildup, and it's worth persevering with even if your cat isn't keen at first. Start slowly: get them used to having their mouth touched, then introduce a cat-specific toothpaste on your finger before moving to a small, soft toothbrush. Never use human toothpaste, as it isn't safe for cats.
Our step-by-step guide on how to brush your cat's teeth walks through the desensitisation process in more detail.
Try dental treats or a dental diet
Dental treats are designed with a texture that helps scrape plaque off the teeth as your cat chews. They're a handy add-on to brushing, not a replacement for it, so they sit best alongside a regular oral care routine rather than as a stand-in for it.
Water additives and dental gels
Water additives, dental gels and supplements are an easy, low-fuss way to support oral hygiene, particularly for cats who won't tolerate brushing. They won't undo existing tartar, but they can help slow new plaque from building up.
Book regular vet dental checks
Your vet can spot early dental disease well before it's visible to you, and professional cleans under anaesthetic are sometimes needed to properly remove tartar from under the gumline. For a full rundown on keeping on top of it, our guide to dental care for cats and home dental care for pets cover the basics in more detail.
If you're not sure whether what you're seeing is normal, our guide on how to tell if your pet has dental disease walks through the other signs to watch for.
Cat Bad Breath FAQs
Cat bad breath is common, but it's usually your cat's way of telling you something, most often that dental disease has crept in. Daily brushing, dental treats and regular vet checks go a long way towards keeping it under control. If the smell changes suddenly, or shows up alongside drooling, appetite loss or weight loss, it's worth a vet visit to rule out conditions like kidney disease or diabetes.
References
Cornell University College of Veterinary Medicine, "Bad Breath: Sign of Illness?", Cornell Feline Health Center. Accessed 18 August 2026. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/bad-breath-sign-illness
World Small Animal Veterinary Association (WSAVA), Global Dental Guidelines. Accessed 18 August 2026. https://wsava.org/
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History
Our experts continually monitor the health and wellness space and we update our articles when new information becomes available.
Tue 18 Aug 2026
Written by Dr Gillian Hill BVSc (Hons)Dr Gillian Hill BVSc (Hons)
Veterinarian
Dr. Gillian graduated from the University of Sydney in 2005 with a Bachelor of Veterinary Science. She worked in a number of small animal clinics, before joining the Pet Circle Vet team in 2020. Dr. Gillian has special interests in ultrasonography, surgery and behaviour. Her favourite part of being a vet is being an advocate for the animals. She loves helping owners to make the best, evidence-based decisions for their pets, and seeing the beautiful bond that people have with their fur-babies.
