How is FeLV diagnosed in cats?

FeLV is commonly diagnosed using a blood antigen screening test, followed by PCR testing to confirm the presence of the virus. The vet will make a judgment based on the test results and your cat's clinical signs.

Can a cat with FeLV live with other cats?

FeLV is contagious. Consult your vet to assess the risk of transmission and the necessary precautions before housing an FeLV-positive cat with other cats. Consider isolation or vaccination as preventive strategies.

What can I do at home to help my sick cat?

Monitor your cat's temperature, appetite, stools, and activity level at home, record short videos to share with your vet, and follow your vet's recommendations for check-up schedules.

What follow-up tests are needed for FeLV infection?

Your vet will typically schedule regular blood tests and, when necessary, PCR follow-ups to monitor changes in blood cell counts and viral replication, adjusting the care plan accordingly.

How much do the tests and treatment usually cost?

Costs vary by clinic and region — ask your vet for an estimate before proceeding.

Disease Guide

Feline Leukemia Virus (FeLV) in Cats: Symptoms, PCR Testing & Care Guide [2025]

Feline leukemia virus (FeLV) is a major infectious disease in cats that can cause immunosuppression and tumors. It spreads through saliva and close contact. Infected cats should be kept indoors and receive regular health checks. A vaccine is available for prevention.

Take 1 minute to check the symptoms first

Last updated: 2026/01/05

Pethealthmap Editorial Team

Sources: ISFM, AAFP, National Taiwan University Veterinary Hospital

When to See a Vet

Seek Emergency Care Immediately

•Sudden loss of consciousness or prolonged unresponsiveness requires immediate attention
•Rapid breathing or obvious respiratory distress that persists
•Sudden inability to stand or marked generalized weakness

Schedule a Clinic Visit Soon (within 24–72 hours)

•Persistent fever lasting more than one day — see a vet promptly
•Continuous diarrhea lasting more than one day, or bloody stool accompanied by lethargy
•Staggering gait or noticeably impaired coordination

01What symptoms indicate something is wrong?

FeLV infection can present in many ways, commonly including gastrointestinal symptoms, fever, and decreased energy, and may involve neurological or eye abnormalities. Seek veterinary evaluation promptly if symptoms persist or worsen.

Persistent or recurring diarrhea with changes in stool consistency and color
Recurring fever or difficulty returning to a normal body temperature
Decreased activity, lethargy, or reluctance to interact
Unsteady gait, poor coordination, or frequent stumbling
Red or swollen conjunctiva or abnormal eye discharge
Weight loss or significantly reduced appetite

Seek emergency care immediately if you notice the following symptoms:

⚠️ Seek immediate veterinary care if your cat loses consciousness or becomes completely unresponsive
⚠️ Sudden inability to walk or generalized weakness is also an emergency
⚠️ Severe difficulty breathing requires immediate emergency treatment

02How do you tell if something is wrong? Key home observation points and emergency criteria

Systematically observing and recording your cat's condition at home before visiting the clinic helps the vet quickly understand the situation and speeds up the diagnostic process.

Track the frequency, consistency, and color of your cat's stools each day
Measure and record your cat's temperature at the same time each day (including the time taken)
Observe and note changes in your cat's alertness and activity level
Record any changes in appetite and the amount eaten at each meal, along with the time
Film short videos of your cat walking, moving, or breathing for the vet
Bring all of the above records and videos to the clinic to help with assessment

03How will the vet make a diagnosis? Common diagnostic tests

The vet will assess your cat's overall condition with a physical examination and, based on clinical concerns, arrange blood tests, viral testing, and any necessary imaging or pathology to confirm the diagnosis and evaluate disease progression.

Physical examination

assessment of lymph node size, oral cavity, and overall condition

Blood count and biochemistry

evaluation of blood cell numbers and organ function

Urinalysis

assessment of kidney function and possible urinary tract infection

PCR viral nucleic acid testing

to confirm the presence and replication of the virus

Pathology or tissue biopsy

used for in-depth pathological analysis when necessary

Advanced imaging (e.g. CT scan)

used for complex cases or when a tumor is suspected

04How is FeLV treated and managed after diagnosis? Medication, diet, and care guide

FeLV management focuses on supportive care and treatment of complications. Treatment and monitoring should be individualized, with regular check-ups to assess disease progression and infection control.

Your vet will explain supportive medications, fluid therapy, and infection control principles
Severe cases may require hospitalization for monitoring or blood transfusion
If tumors or malignant changes are present, further management options will be discussed
Regular blood tests and PCR follow-ups will be scheduled to monitor disease progression and infection status
Dietary adjustments, nutritional support, and a home care plan will be established
Regular follow-up visits are recommended; choose a clinic with testing and advanced medical capabilities

05What should you prepare before the vet visit? Key information to help the vet identify the cause quickly

Note when symptoms first appeared and the details of any daily changes

List changes in your cat's diet and water intake over the past week

Record the frequency of bowel movements, stool consistency, and any presence of blood

Bring all current medications, supplements, and vaccination records

Take videos or photos related to the symptoms as a diagnostic aid

When booking, mention the need for PCR or advanced imaging to save time at the appointment

This content is for reference only and cannot replace a professional veterinary diagnosis. If your pet shows signs of illness, please seek veterinary care promptly.