Cat Diseases: Symptoms, Causes and When to Act

Updated: October 22, 2026

Cat diseases can cause changes in appetite, energy, breathing, digestion or behaviour. Seek urgent veterinary care for severe breathing difficulty, collapse, seizures or sudden inability to urinate; contact a veterinarian promptly about other persistent or worsening symptoms.

Signs can be subtle: a cat may hide, eat less or use the litter tray differently. Causes range from infections and parasites to chronic conditions, so symptoms alone cannot confirm what is wrong. This guide to cat diseases explains common warning signs, possible causes and when to act. For more guidance, see these symptoms of diseases in cats and what to do about them. For a step-by-step overview, read this practical guide to recognizing and treating cat diseases.

Which cat diseases are common, and what do they affect?

Common cat diseases affect different systems: chronic kidney disease (CKD) impairs kidney function, diabetes mellitus disrupts glucose regulation, feline panleukopenia (FPLV) causes serious illness, and feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) are distinct viral diseases.

CKD requires veterinary assessment of the individual cat; symptoms alone cannot establish the diagnosis. Diabetes can cause increased thirst and urination, weight loss, lethargy, vomiting, or diarrhea, so these signs warrant veterinary attention.

FPLV is associated with vomiting, diarrhea, fever, lethargy, seizures, and reddened eyes or gums. FeLV may involve a poor coat, fever, lethargy, reduced appetite, or inflamed, pale, or bloody gums; FIV is a separate infection, not another name for FeLV.

What causes upper respiratory infections in cats?

Feline herpesvirus and feline calicivirus are separate viral causes of upper respiratory infections in cats. In a Belgian rescue shelter, Zicola et al. (2009) found feline herpesvirus prevalence of 20.1% and feline calicivirus prevalence of 33.1%; these figures describe that shelter, not a universal rate for cats.

Feline herpesvirus and feline calicivirus can both be associated with respiratory illness, but identifying which cause is involved matters for guiding care. A cat showing respiratory signs needs veterinary assessment to help determine the cause and appropriate next steps.

Which symptoms mean a cat needs urgent veterinary care?

Seek urgent veterinary care for suspected pyometra, seizures, repeated vomiting or diarrhea, marked lethargy, fever, pale or bloody gums, or sudden behavior changes. These signs can accompany serious conditions, and a veterinarian should assess the cat promptly rather than waiting to see whether they pass.

Pyometra is an emergency infection of the uterus in an unspayed female cat and requires urgent veterinary care. Feline panleukopenia can cause seizures, repeated vomiting or diarrhea, marked lethargy, and fever; these symptoms warrant prompt attention. Keep a cat with suspected panleukopenia away from other cats while arranging veterinary advice.

Other warning signs

Increased thirst and urination alongside weight loss can indicate diabetes mellitus, but only a veterinarian can investigate the cause. Pale, bloody, or inflamed gums and sudden behavior changes are among the signs associated with feline leukemia virus (FeLV); do not dismiss them or try to diagnose the cause at home.

How can routine veterinary care help detect cat diseases?

Routine veterinary care helps detect cat diseases by allowing a veterinarian to assess changes over time, examine the cat, and decide whether further testing is needed. Keep notes on drinking, urination, appetite, weight, coat condition, and activity; these observations can help the veterinarian interpret what has changed and when.

Use life-stage guidance and clinical assessment

The 2021 AAHA/AAFP Feline Life Stage Guidelines offer owners a checkable reference for discussing care suited to a cat’s life stage with a veterinarian. They were published in the Journal of Feline Medicine and Surgery, volume 23, issue 3, pages 211–233, and the Journal of the American Animal Hospital Association, volume 57, issue 2, pages 51–72.

A list of symptoms cannot diagnose chronic kidney disease (CKD), diabetes, feline immunodeficiency virus (FIV), feline leukemia virus (FeLV), or cancer: signs such as changes in appetite, weight, or activity can have different causes. A veterinary examination is needed to determine what is happening and whether tests or treatment are appropriate; share your notes and raise any new or persistent changes at the appointment.

When do symptoms or prevention advice have limits?

Symptoms and prevention advice have limits because vomiting, lethargy and appetite changes can occur in more than one cat disease; none identifies a diagnosis on its own. For example, vomiting and lethargy are listed among signs of feline panleukopenia, diabetes and feline leukemia virus, so a veterinarian must assess the cat rather than infer the cause from one sign.

Belgian shelter prevalence figures for feline herpesvirus and feline calicivirus describe the cats in those shelter populations, not an individual pet’s chance of infection.

When to seek veterinary advice

Squamous cell carcinoma is another condition to discuss with a veterinarian, but a symptom list cannot confirm cancer; diagnosis requires veterinary assessment. Do not wait for a full set of signs if a cat has a seizure or pyometra is suspected: pyometra is an emergency uterine infection in unspayed female cats, and prompt veterinary advice is warranted.

Key takeaways

• CKD, diabetes, FPLV, FIV, and FeLV are distinct conditions, not interchangeable diagnoses.
• Increased thirst and urination with weight loss are diabetes warning signs.
• Suspected pyometra in an unspayed female cat is an emergency.
• Feline herpesvirus and feline calicivirus commonly cause upper respiratory infections.
• The Belgian shelter figures—20.1% for herpesvirus and 33.1% for calicivirus—are specific to that study population.

Common questions