Red eyes in cats may indicate conjunctivitis, infections, allergies, or trauma, and prompt veterinary evaluation helps prevent complications.
Quick Answer
When a cat has red eyes along with losing weight, the combination may indicate a more significant underlying condition. Weight loss alongside another symptom may indicate a chronic or systemic condition such as hyperthyroidism, kidney disease, inflammatory bowel disease, or cancer. These conditions are more common in older cats. A veterinarian can perform blood work and other diagnostics to identify the cause. Red eyes in cats may be caused by conjunctivitis, eye infections, allergies, trauma, corneal ulcers, glaucoma, or upper respiratory infections. Redness accompanied by discharge, squinting, swelling, or changes in the eye appearance should be evaluated by a veterinarian. Sudden redness, especially with pain, warrants prompt attention. Contact a veterinarian if both signs are present, especially if either is severe or worsening.
SYMPTOM TRIAGE
Answer a few questions about your cat's signs and receive general guidance on how urgently to seek veterinary care.
This tool does not diagnose conditions or replace a veterinarian.
What Red eyes Can Look Like
Red eyes in cats may involve redness of the conjunctiva (the tissue lining the eyelids and white of the eye), the sclera (white of the eye), or the tissues around the eye. The redness may be in one or both eyes and may be accompanied by discharge, swelling, squinting, or cloudiness. When red eyes occurs alongside losing weight, the combination provides important information about what may be happening. Weight loss alongside another symptom may indicate a chronic or systemic condition such as hyperthyroidism, kidney disease, inflammatory bowel disease, or cancer. These conditions are more common in older cats. A veterinarian can perform blood work and other diagnostics to identify the cause.
What May Be Associated with Red Eyes
Similar signs can have different causes, and the following are possible explanations a veterinarian may consider.
Conjunctivitis
Inflammation of the conjunctiva is a common cause of red eyes in cats. It may be caused by infections (particularly feline herpesvirus), allergies, or irritants.
Eye Infections
Bacterial, viral, or fungal infections can cause redness, discharge, and discomfort.
Upper Respiratory Infections
Feline herpesvirus and calicivirus can cause eye redness along with sneezing and nasal discharge.
Allergies and Irritants
Dust, pollen, mold, and household chemicals can cause eye redness.
Corneal Ulcers
A scratch or ulcer on the cornea causes redness, pain, squinting, and tearing.
The Combination of Red Eyes and Losing Weight
Weight loss alongside another symptom may indicate a chronic or systemic condition such as hyperthyroidism, kidney disease, inflammatory bowel disease, or cancer. These conditions are more common in older cats. A veterinarian can perform blood work and other diagnostics to identify the cause. The presence of both signs together may narrow the list of possible causes and help a veterinarian prioritize diagnostic steps.
What to Monitor
Tracking details helps a veterinarian assess the situation.
- Whether one or both eyes are red
- Type of redness: Diffuse, localized, or around the eye
- Other eye signs: Discharge, swelling, squinting, cloudiness, or bleeding
- Whether the cat paws at or rubs the eye
- Other signs: Sneezing, nasal discharge, lethargy, or reduced appetite
- Duration: How long the redness has been present
- When each sign started and whether they began at the same time
What You Can Safely Do Next
Do not apply human eye drops, especially those containing steroids, as they can worsen certain conditions. Keep the cat in a clean environment. Prevent the cat from pawing at the eye. If redness persists beyond a day, is accompanied by discharge, squinting, swelling, or pain, or only one eye is affected, contact a veterinarian promptly. When red eyes and losing weight occur together, do not delay in seeking veterinary guidance, as the combination may indicate a more significant issue.
When to Contact a Veterinarian
Some situations require immediate veterinary attention, while others may allow for monitoring. When in doubt, contacting a veterinarian is the safest approach.
Emergency Signs
Contact a veterinarian or emergency clinic immediately if you observe any of the following:
- Red eyes with sudden changes in eye appearance (cloudiness, swelling)
- Redness with squinting and apparent pain
- Redness with the eye appearing enlarged or very painful
- Redness with bleeding in or around the eye
- Redness with lethargy or refusal to eat
These signs may indicate a serious condition that requires prompt evaluation. In the US, the ASPCA Animal Poison Control Center can be reached at 888-426-4435 if toxin exposure is suspected. In the UK, contact your veterinarian or the Veterinary Poisons Information Service for guidance.
Non-Urgent Signs
The following may warrant a routine veterinary call rather than emergency care:
- Mild redness that resolves within hours with no other signs
- Brief redness after exposure to dust or irritants that resolves quickly
When red eyes occurs alongside another sign, veterinary evaluation is recommended sooner rather than later, as the combination may indicate a more significant condition.
Frequently Asked Questions
Why are my cat eyes red?
Red eyes in cats are commonly caused by conjunctivitis, infections, allergies, irritants, trauma, or corneal ulcers. The cause is often identified through veterinary examination. If redness persists or is accompanied by discharge or squinting, a veterinarian should evaluate the cat.
Can I use human eye drops for my cat red eyes?
No. Human eye drops, especially those with steroids, can be harmful to cats. Some ingredients can worsen conditions like corneal ulcers. Only use eye medications prescribed by a veterinarian for your cat specific condition.
What does it mean when my cat has red eyes and losing weight?
The combination of red eyes and losing weight may indicate a more significant issue than either sign alone. Weight loss alongside another symptom may indicate a chronic or systemic condition such as hyperthyroidism, kidney disease, inflammatory bowel disease, or cancer. These conditions are more common in older cats. A veterinarian can perform blood work and other diagnostics to identify the cause. A veterinarian can assess both signs together and recommend appropriate diagnostics and care.
SYMPTOM TRIAGE
If you are concerned about your cat's red eyes and losing weight, use the symptom triage tool to get general guidance on how urgently you should seek veterinary care based on the signs you are observing.
This tool provides general information and does not replace a veterinarian's diagnosis.
Sources
- Cornell Feline Health Center. "Eye Disorders in Cats." Retrieved July 2026.
- Merck Veterinary Manual. "Eye Diseases in Cats." Retrieved July 2026.
- VCA Hospitals. "Conjunctivitis in Cats." Retrieved July 2026.
- American Veterinary Medical Association (AVMA). "Eye Health and Your Pet." Retrieved July 2026.
Disclaimer
This article and the PawAI Symptom Triage tool provide general information and do not replace examination, diagnosis, or treatment by a licensed veterinarian. If your cat shows emergency signs, contact a veterinarian or emergency clinic immediately.