What an unusual breath smell can mean
Ordinary bad breath is most often linked to plaque and periodontal disease. A smell with a distinct “character” may have another cause. This is a guide, not a diagnosis: a pet can have both diseased teeth and a general illness.
- Acetone, sweet, “fruity” → possible diabetic ketoacidosis → see a vet urgently; tests for glucose and ketones.
- Urine, ammonia → possible kidney disease → general vet: blood biochemistry, urinalysis.
- Fish → anal glands, fish-based food, sometimes gum inflammation → general vet, then a dentist if needed.
- Rot → most often the mouth → veterinary dentist.
Acetone breath: possible diabetic ketoacidosis
When diabetes mellitus is not under control, the body breaks down fat intensively and produces ketone bodies; one of them, acetone, is breathed out.
Diabetic ketoacidosis is a life-threatening complication that needs immediate treatment and often hospitalisation. It is usually preceded by signs of diabetes: the pet drinks a lot, urinates often and loses weight despite a good appetite. Later come vomiting, refusing food, lethargy, weakness and rapid breathing.
Not everyone can smell acetone, and its absence does not rule out diabetes — go by your pet’s overall condition.
Breath that smells of urine or ammonia: possible kidney disease
When the kidneys filter the blood poorly, urea builds up in it (uraemia). Bacteria in the saliva break urea down into ammonia, so the breath may smell of urine.
In chronic kidney disease, one of the first signs is often increased thirst and urination. Later there may be reduced appetite, weight loss, vomiting, lethargy and ulcers in the mouth. These make eating painful, and an owner may think the problem is the teeth.
The kidneys are checked by a general-practice vet: blood biochemistry, urinalysis and, if needed, ultrasound and blood pressure measurement. Dental treatment is possible in a pet with kidney disease, but with an individual anaesthetic plan.
Fishy breath: most often the anal glands
Dogs and cats have anal glands (anal sacs) next to the anus. Their secretion has a pungent smell often compared to rotten fish. If the glands are full or inflamed, the pet licks under its tail or scoots along the floor — and the smell ends up in the mouth.
Other possible causes are fish-based food or treats (the smell is usually short-lived, after meals) and gum inflammation. If the glands are fine and the smell persists after a change of food, book a dental examination.
Rotten-smelling breath in a dog or cat
A strong rotten smell most often has a dental source:
- periodontitis with deep pockets where anaerobic bacteria multiply;
- dead (necrotic) tissue — after an injury, in severe periodontitis, and in cats with chronic gingivostomatitis;
- a broken tooth with an infected pulp, or an abscess at the root;
- a growth in the mouth;
- a foreign body — a splinter or bone stuck between the teeth or wedged across the palate.
More detail in the articles on bad breath in dogs and in cats and on the symptom page bad breath. A similar smell can also come from diseases of the nose, throat or digestive tract — if no cause is found in the mouth, investigations continue.
Which vet to see first
If a pet has both a general illness and diseased teeth, dental treatment is planned together with the general vet — once the pet’s condition is stable.
- 01
Assess your pet’s general condition
Thirst, urination, appetite, weight, vomiting, licking under the tail.
- 02
General-practice vet
Blood and urine tests: glucose, ketones, kidney values. With warning signs — the same day.
- 03
Dental examination
If the tests are normal or the smell is rotten — a dental consultation. If you are not in Kyiv — an online consultation.
- 04
Diagnostics under anaesthesia
Examination of every tooth, probing and dental radiography as part of COHAT.
How much a veterinary dental consultation costs
Bring your test results to the consultation or send them for an online consultation.
When to see a vet
- Acetone breath together with vomiting, lethargy, rapid breathing or refusing food — go to a veterinary clinic the same day.
- Your pet has suddenly started drinking a lot and urinating often, or is losing weight despite a good appetite.
- Breath that smells of urine together with reduced appetite, vomiting or mouth ulcers.
- A cat has not eaten for a day or longer.
- A rotten smell together with facial swelling or blood from the mouth.
What you can do at home
- Measure how much water your pet drinks in a day — this figure will help the vet.
- Note how often your pet urinates, whether appetite and weight have changed and whether there has been vomiting.
- Watch whether your pet licks under its tail; if it lets you, photograph the teeth and gums.
- Bring previous test results and a list of medicines to the appointment.
What not to do at home
- Don’t restrict water for a pet that drinks a lot — it can lead to dehydration.
- Don’t mask the smell with sprays, gels or human mouthwash.
- Don’t give human medicines: ibuprofen and paracetamol are dangerous for dogs and especially for cats.
- Don’t wait for a planned dental clean if acetone breath comes with vomiting or lethargy.
Frequently asked questions
A sweetish acetone smell can be caused by ketone bodies in uncontrolled diabetes mellitus, in particular in diabetic ketoacidosis. If your dog is also drinking a lot, vomiting or lethargic, see a vet the same day.
Breath that smells of urine or ammonia can be linked to kidney disease, especially if the pet is drinking a lot and losing weight. The kidneys are checked with blood biochemistry and a urinalysis by a general-practice vet.
Often because of anal gland secretion that the dog licks up. Fish-based food or treats can also cause it, and sometimes gum inflammation. If the glands are fine and changing the food doesn’t help, a dental examination is needed.
Most often the cause is found in the mouth: periodontitis, dead tissue, an infected tooth. But not always: a similar smell can come from diseases of the nose, throat or digestive tract, so if no cause is found in the mouth, investigations continue.
Sources and professional guidelines
- Merck Veterinary Manual — Disorders of the Pancreas in DogsDiabetes mellitus and diabetic ketoacidosis in dogs: signs and urgency (for owners)
- Merck Veterinary Manual — Diabetes Mellitus in Dogs and CatsClinical signs of diabetes and ketoacidosis in dogs and cats
- Merck Veterinary Manual — Noninfectious Diseases of the Urinary System in DogsChronic kidney disease: thirst, mouth sores, diagnosis with blood and urine tests
- Cornell University — Chronic Kidney Disease (cats)Chronic kidney disease in cats: signs and laboratory diagnosis
- Merck Veterinary Manual — Disorders of the Rectum and Anus in DogsAnal sac disease: strong-smelling secretion and signs
- AAHA Dental Care Guidelines for Dogs and CatsClinical guidelines for dental care
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