Diagnosis
How FIP is investigated
- Author
- FIP Together editorial team
- Veterinary review
- Pending
- Published
- 16 Oct 2026
- Last reviewed
- Not yet
This article hasn't yet been reviewed by a veterinarian. It is based on the published sources listed below.
There is no single simple test that confirms FIP in every cat. Veterinarians usually combine the cat's history, an examination and several test results to decide how likely FIP is. That's why owners often hear “suspected FIP”.
Tests that may be used
- Blood tests: complete blood count and biochemistry, including proteins (albumin, globulin) and liver values.
- Analysis of fluid, if present: its appearance, protein content and cells. Some tests look for the virus in the fluid.
- Imaging: ultrasound or X-rays to look for fluid and changes in organs or lymph nodes.
- Tissue samples in some cases, to look for the virus within inflamed tissue.
- Coronavirus antibody tests, which show exposure to the virus but cannot by themselves confirm FIP.
Limitations
Each test has limits. A positive or negative result rarely tells the full story on its own. Your veterinarian weighs everything together, and may recommend repeating tests over time.
Keep copies of every report. FIP Together's Medical Records section lets you store them and compare blood values across dates.
Sources
- Thayer V, et al. 2022 AAFP/EveryCat Feline Infectious Peritonitis Diagnosis Guidelines. J Feline Med Surg. 2022;24(9):905–933.
- Tasker S, et al. Feline Infectious Peritonitis: European Advisory Board on Cat Diseases Guidelines. Viruses. 2023;15(9):1847.
- Pedersen NC. An update on feline infectious peritonitis: diagnostics and therapeutics. Vet J. 2014;201(2):133–141.
This article is general information, not veterinary advice. It can't account for your cat's individual situation. Always follow the guidance of the veterinarian treating your cat.