Hearing the word “cancer” is frightening, and it’s natural to hope a symptom has an innocent explanation. The tricky part with cats is that many serious illnesses, including cancer, can begin with quiet, easy-to-miss changes. Cats often carry on as normal until they simply can’t anymore.
The goal isn’t to diagnose your cat at home. It’s to notice changes early, so your vet has the best chance of finding the cause and offering treatment options.
Below are five warning signs that deserve attention, especially when they appear together or persist.
Why cancer can be hard to detect in cats
Cats are instinctively private when they feel vulnerable. It’s common for a poorly cat to become less social, hide more, or change routines in subtle ways that look like “moods” rather than symptoms.
That’s one reason veterinary charities stress that signs of cancer often overlap with many other conditions. Even when you’re unsure, a vet check is important.
1) New lumps, bumps, or swelling
If you feel something that wasn’t there before under the chin, along the ribs, on a leg, on the tummy, or anywhere else, book a vet appointment. A lump might be benign, but you can’t tell by feel alone, and some cancers are most treatable when caught early.
Practical tip: a quick weekly check
Once a week, run your hands gently over your cat while they’re relaxed, during a cuddle or brushing session. You’re not searching for perfection, just learning what “normal” feels like for your cat.
Common misconception: A lump always means cancer. This isn’t true. Many lumps are non-cancerous, but they still deserve checking.
2) Unexplained weight loss or a body shape that looks different
Weight loss is one of the most consistent red flags vets mention. Some cats lose weight even if they seem to be eating, and it can creep up on you when you see them every day.
Practical tips
- Weigh your cat monthly if possible. Many owners use baby scales for smaller cats.
- If you don’t have scales, notice whether your cat feels lighter when you lift them or if their spine or hips feel sharper than usual.
3) Appetite changes that don’t bounce back
Skipping a meal now and then can happen. But a noticeable reduction in appetite, especially lasting more than a day, or a sudden change in enthusiasm for food should be taken seriously.
Cats can also eat differently when something hurts. Dropping food, chewing on one side, licking lips repeatedly, or walking away after a few bites can point to dental disease, mouth pain, or other problems, including cancers affecting the mouth or digestive system.
Practical tip
If you have more than one cat, consider feeding separately for a few days when you’re worried. In multi-cat homes it’s easy to miss who is, or isn’t, eating.
Common misconception: My cat is just being fussy. Cats can be picky, but a consistent appetite shift, especially with weight loss, is a reason to call the vet.
4) Behaviour changes: hiding, withdrawing, or “not quite themselves”
A cat that suddenly stops greeting you, hides in unusual spots, becomes less tolerant of touch, or seems generally quieter may be telling you they don’t feel right.
Cancer is one possible cause, but so are pain, infection, arthritis, thyroid problems, and more. The important point is that a new pattern matters, particularly if it lasts.
Practical tip
Write down what you’re seeing, when it started, how often it happens, and what else changed. A short timeline helps your vet immensely.
5) Changes in litter tray habits
The litter tray can reveal early clues because it’s one of the few places where you get daily feedback.
Watch for:
- Straining or repeated trips to the tray
- Blood in urine or stool
- Diarrhoea or very hard stools
- Going outside the tray
- A strong, unusual smell that doesn’t resolve with normal hygiene
These signs can be linked to many conditions, from stress to infections, but they’re also on the broader list of warning signs vets discuss when talking about serious illness.
Where Pacha Litter can help: A consistent litter routine can make it easier to notice changes quickly, such as reduced output, unusual colours, or repeated straining. Pacha Litter may support day-to-day monitoring by making the tray easier to keep clean and changes easier to spot. It is not a diagnostic tool, but it can help you bring clearer observations to your vet.
Urgent note: If your cat is straining to wee, visiting the tray repeatedly with little output, or seems distressed, treat it as an emergency. This can indicate a blockage, which can be life-threatening.
Extra warning signs worth mentioning
Even though we’re focusing on five, these symptoms also deserve attention, especially if they persist:
- Vomiting or diarrhoea that keeps happening
- Sores that don’t heal or scabs on ear tips or nose, particularly in light-coloured cats
- Difficulty breathing, coughing, or rapid breathing
- Bad breath or mouth odour with drooling or difficulty chewing
When should you call the vet?
Call your vet as soon as you notice a new lump, weight loss, an appetite change lasting more than 24 hours, repeated vomiting or diarrhoea, or any persistent “not themselves” behaviour.
If you’re unsure, it’s still worth phoning. Your vet team can advise whether to monitor at home, book a routine appointment, or seek urgent care.
Final thought
Cancer in cats can be difficult to spot, not because owners don’t care, but because cats are brilliant at keeping secrets. The best approach is calm, consistent observation. Know what’s normal for your cat, notice what changes, and act early when something doesn’t add up.
