Table of contents
Key Takeaways
- Testing for both feline leukemia and FIV is done with a single simple blood draw, with results available nearly immediately in the clinic.
- Most cats are recommended for at least one combined FeLV and FIV test in their lifetime, with more frequent testing for cats that go outside or have exposure risk.
- Neither disease has a cure, making early detection, vaccination against feline leukemia, and risk reduction the most important tools for protecting your cat.
Feline leukemia and FIV don't always come up in casual conversation about cat health, but they're two of the more serious conditions cats can face. Both are contagious between cats, both are incurable, and both can hide for years before a cat looks sick. Feline leukemia and FIV testing is how our vets find out a cat's status early, while there is still time to protect other cats in the home.
To walk through it, we sat down with Dr. Christie Long, Chief Medical Officer at Modern Animal. She explains who should be tested and how often, how the test works, and what to do with the result.
What Is Feline Leukemia?
Feline leukemia virus, or FeLV, is a retrovirus that spreads from cat to cat through close contact. Despite the name, it does not always cause leukemia in the classic sense, but it can cause blood cancers and it steadily weakens the immune system.
"Feline leukemia is a viral disease that's transmitted from cat to cat, and like its name, it actually can produce blood cancers," Dr. Long said. "So it's a very serious disease."
What it does. The virus infects white blood cells and bone marrow. Over time it can cause lymphoma, severe anemia, and an immune system too weak to fight off ordinary infections.
What it looks like. Early on, nothing. As it progresses, common signs are weight loss, pale gums, recurring fevers, swollen lymph nodes, and infections that keep coming back.
Why there is no way back. "Feline leukemia is not a disease that we can cure, so once they get the disease, they are infected for life," Dr. Long said. Most cats with a persistent infection die within a few years of diagnosis. "That's why the vaccination is important to protect them."
Why the vaccine comes up at kitten visits. Because the infection is permanent and the disease is often fatal, our vets recommend the feline leukemia vaccine for kittens as a matter of course. "We'll often recommend this vaccination in kittens, even if you think the cat is going to live its life inside," Dr. Long said. Testing comes first, because the vaccine only helps a cat that is not already infected.
What Is FIV?
Feline immunodeficiency virus, or FIV, is a retrovirus in the same family as HIV. It attacks the immune system slowly, over years, and most commonly spreads through deep bite wounds between cats.
What it does. FIV targets the white blood cells that coordinate immune defense. After a long silent phase, the immune system weakens enough that the cat becomes prone to infections it would normally clear, especially of the mouth and skin.
How it differs from feline leukemia. Both viruses weaken the immune system and neither can be cured, but the outlook is different. FIV progresses slowly, and a cat diagnosed early and kept indoors on good preventive care often lives a normal lifespan. FeLV is more aggressive and more contagious, and its outlook is worse.
The vaccine question. There is no FIV vaccine currently recommended in the United States. For FIV, testing and avoiding bite exposure are the tools that matter.
How are FeLV and FIV Transmitted?
Both viruses require cat-to-cat contact. Neither infects people or dogs. The difference is in what kind of contact it takes.
Feline leukemia. FeLV is shed in saliva, nasal secretions, urine, feces, and milk. It passes between cats through mutual grooming, shared food and water bowls, shared litter boxes, and bite wounds. An infected mother passes it to her kittens. Because friendly contact is enough, FeLV moves easily through a household.
FIV. FIV is concentrated in saliva and needs to get under the skin, so the main route is a deep bite during a fight. That makes unneutered outdoor males the most common carriers. Casual contact and shared bowls carry very low risk, which is why FIV-positive and negative cats can often live together if they do not fight.
Who is at risk. Outdoor cats, cats that fight, cats living with a positive cat, and cats of unknown history are all higher risk. Indoor-only cats with tested-negative housemates are low risk, but not zero.
Which Cats Should Be Tested?
Almost every cat should be tested at least once. Cats with ongoing exposure risk should be tested more often, on a schedule your vet sets based on their lifestyle.
"In most cats, we recommend testing for feline leukemia and feline immunodeficiency virus once in their lifetimes," Dr. Long said. "But if your cat goes outside frequently, your veterinarian may recommend routine testing more often if they have a risk of being exposed to these diseases."
Kittens and new cats. Every kitten and every newly adopted cat should be tested before joining a household, ideally before meeting the resident cats and before the FVRCP and feline leukemia vaccine series begins. Shelters often test, but not always.
Indoor cats. An indoor cat with a negative test and no exposure usually does not need to be retested. The one lifetime test rules out an infection picked up before adoption and confirms the vaccine is going into a cat that can benefit from it.
Outdoor and high-risk cats. Cats that roam, cats that come home with bite wounds, and cats living with a positive housemate should be retested. For a cat with regular outdoor access, many vets recommend testing yearly at the annual wellness exam.
After a known exposure. After a bite from an unknown cat, repeat the test 30 days or more later, because it takes time for a new infection to become detectable.
Sick cats. Any cat with unexplained weight loss, recurring infections, chronic mouth inflammation, or anemia should be tested regardless of prior results.
What Does FeLV and FIV Testing Involve?
It is a small blood sample and a few minutes of waiting. Both viruses are checked from the same sample, in the clinic, and you usually have the answer before you leave.
"Testing for feline leukemia and FIV is just a matter of a simple blood draw, and we can usually do the test right in our clinics and have the results available nearly immediately," Dr. Long said.
How the test works. The in-clinic kit looks for FeLV antigen, meaning pieces of the virus, and FIV antibodies, meaning the cat's immune response. Results appear in about ten minutes.
Two limits worth knowing. A recently exposed cat may not test positive for several weeks. And kittens under about six months can test FIV-positive from maternal antibodies without being infected, so a positive in a young kitten should be repeated at six months.
Confirming a positive. A positive on the in-clinic test is a reason to look closer, not a final answer. Our vets typically confirm with a repeat test after a few weeks or a send-out lab test. Book an appointment if your cat is due for a first test or a recheck.
What happens if my cat tests positive?
A positive result is serious, but it is not an emergency, and for FIV it is often not a shortened life. It changes how you manage your cat rather than whether you can.
For an FIV-positive cat. Keep the cat indoors, schedule wellness exams twice a year, and keep up dental care, since mouth disease is the most common complication. Use year-round flea and tick prevention for cats, since parasites carry infections a weakened immune system struggles with. With that care, many FIV-positive cats live into their teens.
For an FeLV-positive cat. The same steps apply, with more urgency, and the cat should be kept strictly indoors and separated from uninfected cats. Regular bloodwork helps catch anemia and early cancers. The outlook is more guarded than with FIV, but some cats live comfortably for years.
Other cats in the home. If one cat tests positive for FeLV, every other cat should be tested and vaccinated. If one tests positive for FIV, housemates should be tested, but separation is usually only needed if the cats fight.
Support along the way. Your vet will walk you through what the result means. Modern Animal All Access and Essential members can also follow up with questions anytime through 24/7 Virtual Care.
Keeping records. "Just like every other vaccination your cat gets, the record of the feline leukemia vaccination will be present in the Modern Animal app," Dr. Long said. "And you can easily download a record of all your cat's vaccinations and share it with places like boarding facilities or groomers."
What does FeLV and FIV testing cost?
Testing costs at Modern Animal vary depending on where you live. The combined FeLV and FIV test is typically run as part of a wellness visit, and the overall cost of that visit depends on what else is recommended.
What affects the price. A test run during a kitten or wellness exam is billed alongside that exam, and any confirmatory send-out testing after a positive result is priced separately. For most indoor cats, the test is a one-time item.
For a full breakdown of service and test pricing at Modern Animal, visit modernanimal.com/pricing. Everything is listed transparently so you know what to expect before you come in.
The bottom line. Testing for feline leukemia and FIV is one of the simplest things you can do to stay ahead of your cat's health. One blood draw, ten minutes, and you know where your cat stands.
If your cat hasn't been tested or is due for a recheck, book an appointment through the Modern Animal app. For more on preventive care for cats, visit the Modern Animal blog.
Frequently Asked Questions
Dr. Long says most cats should be tested once in their lifetime, and cats that go outside frequently may need routine testing more often based on their exposure risk. In practice, every kitten and newly adopted cat gets tested once, and outdoor cats, cats with bite wounds, and cats living with a positive housemate are retested, often yearly.
Dr. Long describes it as a simple blood draw, run right in our clinics with results available nearly immediately. Both viruses are checked from a single small sample, and results take about ten minutes. A positive result is usually confirmed with a second test before it is treated as final.
First, the result is confirmed, especially in kittens under six months, who can carry maternal antibodies without being infected. If it holds, keep the cat indoors, schedule wellness exams twice a year, and stay on top of dental care and parasite prevention. Many FIV-positive cats live long lives with that care. Housemates should be tested but usually only separated if the cats fight.
Both are retroviruses that weaken the immune system and cannot be cured, but they behave differently. Feline leukemia spreads through everyday contact, can cause blood cancers, and has a more guarded outlook. FIV spreads mainly through bite wounds, progresses slowly, and cats diagnosed early often live normal lifespans. A vaccine exists for feline leukemia but not for FIV.
Only with tested-negative, vaccinated housemates, and ideally not at all. Feline leukemia spreads through grooming and shared bowls, so an FeLV-positive cat is a real risk to housemates. If separation is not possible, every other cat should be tested and vaccinated. An FeLV-positive cat should also be kept strictly indoors.
Yes, at least once. A baseline test rules out an infection picked up before adoption and confirms the feline leukemia vaccine is going into a cat that can benefit from it. Dr. Long notes our vets often recommend the vaccine for kittens even if the cat is expected to live indoors. An indoor cat that tests negative usually does not need to be retested.