Calming a cat anxious about a sick housemate

This is a situation a lot of people don't anticipate — a cat becoming visibly anxious not because of a new pet or a house move, but because another cat in the home has changed. When a companion animal becomes ill, their scent changes, their movement changes, their behaviour changes, and resident cats absolutely pick up on that. It can genuinely destabilise them. Cat anxiety is also famously easy to miss until it's built up, so the fact you're paying attention now is a good sign. Can you tell me what you're seeing from your British Shorthair — hiding, aggression, over-grooming, something else? And do you know roughly when it started relative to the other cat's illness?

That paints a very clear picture. Withdrawal and avoidance like that — especially abandoning shared spaces — is a classic stress response. He's not being difficult, he's genuinely unsettled by the fact that his companion smells and moves differently. From his perspective, something is wrong with her and he doesn't know what. Are the two cats still spending any time in the same room, or are they actively avoiding each other? And is your British Shorthair eating and using the litter tray normally, or has that been affected too?

Good — eating and litter habits holding steady is reassuring, and it tells me this is stress rather than something physical you'd need the vet for urgently. The withdrawal and reduced social engagement with you is very typical of a cat trying to manage an environment that feels uncertain. The product I'd point you to here is the Feliway Friends diffuser. It's specifically formulated for multi-cat tension — it uses a synthetic version of the feline appeasing pheromone that mother cats produce, which is different to the single-cat Feliway Classic. It won't treat your older cat's illness, but it works on the emotional environment between them. Plug it into the room where they spend the most time together, or where the shared sleeping spots used to be. One diffuser covers roughly 50–70 square metres and you leave it running continuously. You should start to see a difference in two to four weeks, though some cats respond sooner. It's worth committing to a full month before you judge it.

Go with the main living area where they used to share space — the goal is to make that zone feel safe again so he's drawn back to it, rather than reinforcing the hiding spot. If the bedroom and living area are quite separate, a second diffuser in the bedroom wouldn't hurt, but start with one in the shared space first. Also worth noting: don't move your older cat's feeding spot or litter tray during this period if you can avoid it. Keeping her routine stable reduces the scent and behavioural disruption your British Shorthair is reacting to. The situation may also settle naturally as your older cat stabilises on her medication and returns to something closer to her previous self — the Feliway Friends just supports that process and takes the edge off in the meantime.

Good call. Give it a proper run — four weeks minimum — and keep an eye on whether he starts reusing those shared spaces or seeks you out more. Those are your best early indicators it's working. If after six weeks there's been no shift at all, it's worth a conversation with your vet just to rule out anything else, but for what you're describing this is the right first step.