Is Bad Breath Normal in Cats?
A cat's breath should be relatively neutral. While it may carry a faint fishy or meaty smell after eating, persistent bad breath — known medically as halitosis — is not something to dismiss. Unlike dogs, cats are fastidious groomers and generally maintain good oral hygiene on their own, which means noticeable mouth odour is often a sign that something is wrong. Understanding the most likely causes, ranked by how frequently they occur, will help you decide when to act.
The Most Common Causes of Bad Breath in Cats
1. Dental and Periodontal Disease
By far the most frequent cause of feline halitosis is dental disease. Studies suggest that over 70 percent of cats show signs of periodontal disease by the time they reach three years of age. Plaque builds up along the gumline, hardens into tartar, and provides a breeding ground for bacteria. These bacteria produce volatile sulphur compounds — the same compounds responsible for the characteristic unpleasant smell. As gum disease progresses, pockets form between the teeth and gums, leading to infection, tooth root abscesses, and significant pain.
The World Small Animal Veterinary Association (WSAVA) has published feline dental guidelines recommending annual oral health assessments from a young age, along with proactive home care. Signs that dental disease is behind your cat's bad breath include red or swollen gums, visible tartar (a yellowish-brown crust on the teeth), pawing at the mouth, and difficulty eating.
2. Kidney Disease (Uraemic Breath)
This is the cause that most warrants urgent attention in cats. Chronic kidney disease (CKD) is extremely common in older cats, with some studies estimating that up to 30 percent of cats over 10 years old are affected. When the kidneys fail to filter waste products effectively, urea accumulates in the bloodstream. The body attempts to expel these toxins through respiration, producing a distinctive ammonia-like or "fishy" smell that is quite different from ordinary dental odour.
If your cat's breath smells strongly of ammonia and they are also drinking more than usual, urinating frequently, losing weight, or becoming lethargic, kidney disease must be ruled out as a matter of urgency. Early diagnosis dramatically improves prognosis, so do not delay seeking veterinary advice.
3. Diabetes Mellitus
Diabetic cats may develop a distinctive sweet or fruity smell on their breath, caused by the presence of ketones. This occurs when the body breaks down fat for energy instead of glucose — a state known as diabetic ketoacidosis (DKA) in severe cases. DKA is a life-threatening emergency. Other signs of diabetes in cats include increased thirst and urination, weight loss despite a good appetite, and a plantigrade stance (walking with the hocks touching the ground). Any cat with sweet-smelling breath alongside these symptoms requires immediate veterinary assessment.
4. Liver Disease
A musty, almost faecal odour on a cat's breath can indicate liver disease. The liver plays a central role in detoxifying the blood, and when it fails, toxins including ammonia can build up and be released through the breath. Liver disease in cats often accompanies other symptoms such as jaundice (yellowing of the skin, whites of the eyes, or gums), vomiting, loss of appetite, and a swollen abdomen.
5. Oral Ulcers and Calicivirus
Feline calicivirus (FCV) is a common upper respiratory infection that can cause painful ulcers on the tongue, palate, and lips. These ulcers can become infected with bacteria and produce a very unpleasant smell. Cats with calicivirus may also sneeze, have a runny nose or eyes, and drool excessively. Other causes of oral ulcers in cats include feline herpesvirus and chronic gingivostomatitis — a severe immune-mediated condition that causes widespread inflammation of the mouth.
6. Oral Tumours
Oral tumours, including squamous cell carcinoma, are unfortunately not rare in cats and can cause a foul smell due to tissue death and secondary infection. They may appear as growths on the tongue, gums, or the back of the throat, and can bleed or ulcerate. Any unexplained lump or lesion in the mouth alongside halitosis should be examined by a vet promptly.
Home Dental Care for Cats
For the majority of cats whose bad breath stems from dental disease, a consistent home care routine makes a real difference. Ideally, toothbrushing should begin when your cat is a kitten, using a soft-bristled cat toothbrush and toothpaste formulated specifically for cats — never use human toothpaste, as fluoride and xylitol are toxic to cats. Even daily finger brushing is beneficial if your cat tolerates it.
For cats who refuse brushing, there are alternative products to consider. Dental gels, water additives, and dental chews all carry the Veterinary Oral Health Council (VOHC) seal of acceptance when they have been shown in clinical trials to reduce plaque or tartar. Dental treats — including a wide range available through Zooplus — can be a useful supplement to a brushing routine, though they are not a replacement for it.
Diet also plays a role. Cats fed wet food exclusively may accumulate tartar more quickly than those who eat dental-specific dry kibble, as the mechanical action of chewing larger pieces helps to scrape the tooth surface. Some veterinary prescription dental diets are formulated with larger-than-normal kibble pieces and fibre orientations designed to clean teeth as the cat bites through them.
Professional Dental Cleaning
Even with excellent home care, most cats will eventually need a professional scale and polish under general anaesthesia. Your vet will conduct a thorough examination, probe the gumline, and take dental X-rays to assess root health — damage below the gumline is not visible to the naked eye. The WSAVA guidelines recommend dental X-rays as a standard part of any professional dental procedure.
Do not be put off by the idea of anaesthesia — modern veterinary anaesthetic protocols are very safe, and the risks of leaving dental disease untreated far outweigh the small risks of a routine procedure. Untreated periodontal disease can cause bacteria to enter the bloodstream and affect the heart, kidneys, and liver.
When to See a Vet
You should book a veterinary appointment promptly if your cat's bad breath is:
- Ammonia-like or strongly "fishy" — potential kidney disease, especially in a cat over seven years old
- Sweet or fruity — possible diabetes or diabetic ketoacidosis (seek same-day advice)
- Accompanied by weight loss, increased thirst, lethargy, or changes in urination
- Musty or faecal in character — possible liver disease
- Associated with visible mouth ulcers, bleeding gums, or a lump in the mouth
- Persistent despite good dental hygiene and a recent professional clean
Cats are expert at hiding illness, and halitosis is one of the few outward signs that something may be wrong internally. The PDSA recommends annual health checks for all cats, and twice-yearly checks for those over seven — these appointments are an ideal time to raise concerns about oral health. When caught early, almost all the conditions associated with bad breath in cats are far more manageable, making that vet visit well worth arranging sooner rather than later.