Feline immunodeficiency virus in cats – signs and vet care

Updated 2026-09-30 · 2 sources

Based on: PDSA, International Cat Care (iCatCare)

Book a vet visit

Book a vet appointment if you think your cat has this – a vet needs to confirm it and plan the treatment. FIV is a virus that infects cats and weakens their immune system, making them more prone to illness and infections.

What to do now

What you can do now

Contact your vet.
Note when it started, how often it happens and what else you see.
Take a photo or short video to show the vet.
Keep fresh water available.
Let your cat rest somewhere calm.

Don't

Do not give any human medicine.
Do not wait if it gets worse.

What it is

FIV is a viral infection of cats that can remain in a cat for life.^[2] It weakens the immune system, which can make cats prone to illness and infections.^[1] Some cats with FIV can live happily with the virus for a long time, and the virus may never cause illness in some cats.^[2]

Signs

Weight loss
Fever that returns
Low energy or tiredness
Swollen glands
Inflamed gums and mouth
Ongoing or recurring breathing, eye or intestinal disease
Ongoing skin disease
Ongoing diarrhoea
Sneezing, runny nose or weepy eyes
Taking a long time to recover from infections

gradual

Causes and risk factors

Contact with saliva, usually through a bite from an infected cat

How a vet finds out

A blood test at a veterinary clinic
Testing for antibodies to the virus in the blood
A repeat blood test if needed
Sending a blood sample to an external laboratory for additional testing

How vets treat it

Diet change
Medication
Antiparasitic treatment

What the experts say

“Overview. FIV is a virus that infects cats and weakens their immune system, making them prone to illness and infections. FIV spreads in saliva, usually when an infected cat bites another cat – it doesn’t transfer to humans or other animals.”
— PDSA [1]

“Weight loss ; Recurrent high temperature (fever) ; Lethargy/tiredness ; Enlarged lymph nodes (glands) ; Gingivitis and stomatitis (inflammation of the gums and mouth) ; Chronic or recurrent respiratory, ocular, and intestinal disease ; Chronic skin disease ;”
— International Cat Care (iCatCare) [2]

If your pet is struggling to breathe, has collapsed, is having a seizure or can't stand up: go to the nearest vet now.

Not sure how serious it is?

OkPaw asks a few quick questions about your pet and tells you in 30 seconds whether it can wait. Free on Google Play for Android.

OkPaw is on Android now – an iPhone version is on its way.

Common questions

What is FIV?

FIV is a viral infection of cats that weakens their immune system and can make them prone to illness and infections.^[1]^[2]

How does a vet diagnose FIV?

A vet can diagnose FIV with a blood test that detects antibodies to the virus, with further testing if there is any doubt.^[2]

Can a cat with FIV live happily?

Many FIV-infected cats can live happily with the virus for a long time, and in some cats it may never cause illness.^[2]

Sources

How this page was made: written with the help of AI from the sources below, then checked claim by claim against those sources. Urgency levels follow OkPaw’s fixed safety rules. It is guidance, not a diagnosis. How we write our pages