Early signs of illness in cats and dogs: what to watch for

Cats and dogs are poor reporters of their own condition, and cats are considerably worse than dogs. A species that shows weakness attracts attention it does not want, and the instinct survives domestication intact — which means the point at which an animal looks obviously unwell is usually well past the point at which it first was.

The practical consequence is that the useful signal is rarely a dramatic symptom. It is a change: something the animal has always done that it has stopped doing, or something it has never done that it has started.

Signs that mean the same day, regardless of how the animal seems

Some findings are urgent on their own, even in an animal that is still walking around and greeting you.

For the ingestion row, the useful facts are the product name, its strength, roughly how much is missing, the time, and the animal’s weight — the reasoning behind that list is set out in human medicines and pets.

What to watch at home when nothing on that list applies

Away from the urgent findings, observation is about establishing what has changed and in which direction. Four domains carry most of the information.

Appetite and drinking. Not only whether the animal eats, but how — approaching the bowl and turning away, dropping food, chewing on one side, or eating normally while drinking noticeably more. A marked increase in thirst is as significant as a loss of appetite and is more often overlooked, especially where an animal has access to more than one water source.

Posture, movement and rest. Reluctance to jump, a change in how the animal rises from lying, a shortened stride, a new resting place, or a cat that has moved somewhere it can be alone. Grooming is a good proxy in cats: a coat that has become unkempt over days usually means the animal has stopped grooming, and a cat that has stopped grooming has a reason.

Breathing. The most informative thing an owner can observe, because it needs no handling. Count while the animal is genuinely resting or asleep, watching the chest rise and fall — one rise plus one fall is one breath. A settled cat or dog is usually below about 30 breaths a minute; a resting rate that has risen and stayed up is a reason to call. Panting in a dog after exertion or in warm weather is thermoregulation, not respiratory rate.

Urination and faeces. Frequency, volume, effort, and appearance. Litter trays make this easy to track in cats and are worth using as a source of information rather than only as a chore. Straining with little produced is the emergency; blood, black tarry stools and persistent diarrhoea are all reasons to be seen.

Why a cat that stops eating is different from a dog that does

The 24-hour figure for cats is not a rounded-off version of the dog figure. It reflects a species difference in how fat is handled.

When a cat stops eating, it mobilises body fat to the liver for energy. Feline liver metabolism processes that influx poorly, and fat accumulates in liver cells — hepatic lipidosis — which impairs liver function and can become self-sustaining, since the animal then feels even less inclined to eat. Overweight cats are at higher risk, precisely because there is more fat to mobilise. The condition is treatable and it is much easier to treat early.

Dogs do not have the same vulnerability, so a single missed meal in a bright, well-hydrated dog is a smaller matter. What changes the picture in either species is company: refusal to eat alongside lethargy, vomiting, altered drinking or a change in toileting is a different situation from refusal alone.

What cats hide and how it shows

Because cats mask illness thoroughly, their signals tend to be subtractions rather than additions — things that stopped.

Reduced grooming, shown as a dull or matted coat. A change in resting place, particularly to somewhere enclosed, high, or away from the household. Reduced interaction, or the reverse in a normally independent cat. Sitting hunched with the tail wrapped in. Reluctance to jump onto a surface used every day. A change in litter tray habits, including going elsewhere — which is frequently read as behavioural and is often medical.

None of these is dramatic and none is specific. Their value is cumulative: one is worth noting, two or three together in the same week is worth a call.

What to bring and what to record

A veterinary consultation is short, and the signs are often absent in the room. What survives that constraint is a written timeline.

Record when the change was first noticed and how it has progressed; what the animal has eaten and drunk and when; when it last urinated and passed faeces and what those looked like; the resting respiratory rate if you managed to count it, and temperature if you are able to take it — the ranges are in normal temperature, pulse and respiration. Note body weight if you know it, and whether it has changed.

Then list everything the animal has received: prescribed medicines, over-the-counter products, supplements, parasite treatments, the current diet and any recent change to it, with product names and dates. Bring the packaging where possible — a photograph of the label is enough, and it answers questions that a remembered name does not, since the same brand often exists at more than one strength.

Video is the single most underused tool available to owners. A cough, a limp, a tremor, a collapse or an odd gait is frequently intermittent, and thirty seconds of footage taken at home settles questions that an examination cannot.

Bottom line

Cats and dogs conceal illness, so the reliable signal is a change from what is normal for that individual rather than a dramatic symptom. A short list of findings warrants a same-day call regardless of how the animal otherwise appears: laboured breathing, open-mouth breathing in a cat, straining to urinate with little produced, repeated unproductive retching with a distended abdomen, collapse or seizure, pale or blue gums, profuse or bloody vomiting or diarrhoea, a known ingestion, and penetrating wounds. A cat that has not eaten for around 24 hours needs to be seen because of how feline liver metabolism responds to fasting. Everywhere else, watch appetite and drinking, posture and movement, breathing at rest, and toileting — and treat two mild signs at once, or any sign that is worsening, as a reason to move sooner. Bring a written timeline, the product packaging, and video of anything intermittent.