Cats need nutrients found only in animal tissue. A food labelled "complete" supplies all of them; one labelled "complementary" does not.
Portions are best weighed and split into several small meals, with fresh water always available. Lilies, onions, chocolate and grapes are poisonous to cats.
Cats are obligate carnivores: they need nutrients that are found only in animal tissue, including the amino acid taurine, arachidonic acid and preformed vitamin A. That makes their diet less flexible than a dog's, and dog food, vegetarian diets and most home-made meals do not meet their needs.
Pet food labels in the United Kingdom and the European Union use two terms. A complete food supplies everything a cat needs when fed as directed. A complementary food, which includes most treats and many pouches and tins sold as toppers, does not, and is fed alongside a complete food. The distinction on the label matters more than the brand.
Foods are also made for life stages. Kitten food is denser in energy and protein; senior diets allow for lower activity and ageing kidneys. Neutered cats need fewer calories than entire ones.
Both wet and dry complete foods are nutritionally adequate. Wet food is about three-quarters water, which helps cats that drink little and those prone to urinary problems. Dry food is convenient, keeps for longer in the bowl and suits puzzle feeders, but it is easy to overfeed. Many households give both.
Raw meat diets carry a risk of bacteria such as salmonella for the cat and the people handling the food, and are difficult to balance at home. Any change of diet is made gradually over about a week to avoid upsetting digestion.
The feeding guide on the pack, based on body weight, is a starting point, adjusted according to the cat's condition. On a cat of healthy weight the ribs can be felt easily under a thin covering, and a waist is visible from above. Weighing the day's food is more accurate than judging by eye.
Obesity is one of the most common health problems in pet cats and raises the risk of diabetes, arthritis and urinary disease. Treats count towards the daily amount.
Cats are adapted to eating many small meals. Kittens need three or four meals a day; adults do well on several small portions, and puzzle feeders or food hidden around the house give indoor cats something to work for. A timed feeder helps when the household is out all day.
Fresh water is available at all times, in a wide, shallow bowl placed away from the food and the litter tray. Some cats prefer running water and drink more from a fountain. Most adult cats cannot digest the lactose in cow's milk, which causes diarrhoea; it is not needed after weaning.
Ceramic, glass and stainless steel bowls are easier to keep clean than plastic, which scratches and holds bacteria. Wide, shallow dishes suit most cats better than deep ones. Bowls are washed daily. In a household with several cats each has its own bowl, set apart from the others; feeders that open only for a registered microchip keep one cat from eating another's food or prescription diet.
Lilies are highly poisonous to cats: every part of the plant, including the pollen and the water in the vase, can cause fatal kidney failure. A cat that may have eaten or licked any of these needs a vet without delay.
A cat that stops eating for more than a day needs veterinary attention, since cats that go without food develop liver problems quickly. Gradual weight loss, increased thirst and a sudden ravenous appetite are also reasons for a check, as described under common health problems in cats.