One day they're a tiny ball of fluff attacking your shoelaces, the next they're a sleek young cat eyeing up the kitchen counter. Kittens grow up fast, and at some point you'll wonder whether it's time to move them off kitten food. Here's exactly when to make the change, how to do it without any tummy trouble, and the breed and neutering details most guides leave out.
When to switch from kitten to adult cat food (the short answer)
Most cats are ready to move from kitten to adult food at around 12 months old. Large or slow-maturing breeds often need to wait longer, sometimes until 18 months to two years, because they're still growing.
The reason is simple: kitten food is built for growth, and once your cat has finished growing they no longer need all those extra calories. There's no need to rush it, though. A few weeks either side of their first birthday is perfectly fine, and your vet can confirm the timing for your individual cat.
When you are ready, you'll find suitable recipes in our adult cat food range.
Why 12 months is the usual milestone
Kittens do the vast majority of their growing in their first year. All that rapid development, building muscle, bone and a busy little brain, takes a lot of fuel, which is why kitten food is deliberately more calorie-dense and nutrient-rich than adult food. The nutritional standards set by FEDIAF, the body that governs pet food nutrition across the UK and Europe, set higher minimums for growth than for adult "maintenance", which is the steadier diet a fully grown cat needs (FEDIAF, 2024).
Once growth is done, those extra calories stop being useful and start being stored, especially after neutering (the routine operation that stops a cat being able to breed, which also lowers how much energy they burn). Keeping a fully grown, neutered cat on rich kitten food is one of the easiest ways for the pounds to creep on without anyone noticing.
If you'd like a refresher on what kitten food actually provides and why it's formulated the way it is, we've covered it in our guide to the best food for kittens.
Does breed change the timing?
Yes, and this is the bit most guides skip. Twelve months is the rule of thumb, but it's not one-size-fits-all. Larger, slower-maturing breeds carry on growing well past their first birthday, so they benefit from staying on a growth recipe for longer. International Cat Care notes that a cat's nutritional needs shift as they move through their life stages, and these bigger breeds simply take longer to leave the growing-up phase behind (International Cat).
Breeds that often need a little longer include:
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Maine Coon
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Ragdoll
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Norwegian Forest cat
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Bengal
These cats can keep filling out until around 18 months to two years, sometimes longer, so many owners keep them on kitten or growth food past the 12-month mark. If you've got one of these magnificent big softies, it's worth a quick word with your vet about timing rather than switching by the calendar alone. Our vet partner Dr Scott Miller helps shape our recipes with exactly this kind of individual variation in mind.
Signs your kitten is ready for adult food
Age is a guide, but your cat's body tells the real story. Before you switch, it helps to tick off a few of these:
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They've reached around 12 months and look close to their adult size
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Their growth has clearly slowed or levelled off
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They've been neutered
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Their weight is starting to creep up on kitten food
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Your vet agrees they're ready
If most of these ring true, your cat is very likely ready to make the move. If you're only ticking one or two, there's no harm in waiting a little longer.
How neutering changes when and what you feed
Neutering and food are more closely linked than many owners realise. In the UK, kittens are often neutered from around four months old, partly to help prevent unplanned litters (PDSA). After the operation, a cat's energy needs drop, and neutering is a recognised risk factor for weight gain in adult cats (Foreman-Worsley et al., 2025).
Here's the reassuring part. A 2025 study from the University of Bristol's long-running Bristol Cats study, published in the Veterinary Record, looked at more than 2,000 clinical records from 584 cats and found no difference in long-term bodyweight or body condition between cats neutered at four, five or six months old (Foreman-Worsley et al., 2025). So early neutering itself doesn't doom your cat to weight problems, but the drop in energy needs afterwards does mean it's worth keeping a close eye on portions, and moving to an adult or neutered-cat recipe at the right time. If your cat does need to watch their waistline, a lighter recipe like Fat Cat Slim is designed for exactly that.
How to switch your kitten to adult food, step by step
The golden rule of any food change is to take it slowly. A sudden swap is the most common cause of an upset tummy, so spread the change over about a week or two.
Here's the approach we always recommend:
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Start with around 10% new adult food mixed into 90% of their current kitten food
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Every couple of days, add a little more adult food and a little less kitten food
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Keep going gradually until, by the end of the two weeks, they're fully onto the new food
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If you're mixing wet and dry, just offer them alongside each other rather than blending into one bowl
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Watch their stools as you go, and if things turn loose, simply slow down and ease back a step
Patience really is everything here, especially with fussier cats. For the right amount to feed, follow the guide on the back of the pack, which is tailored to the recipe and your cat's weight. You're moving them onto your chosen adult cat food or wet cat food, and away from their kitten food, so a little overlap of textures and flavours during the change can help win over a hesitant eater.
What actually changes when you move to adult food
Adult food isn't a lesser version of kitten food, it's simply tuned for a different job. The main differences are:
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It's lower in calories, because your cat is maintaining their body rather than building one
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The protein and fat are balanced for steady adulthood rather than rapid growth
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Portions usually shift, so it's a good moment to re-check the feeding guide
Format-wise, adult cats can enjoy wet, dry or a mix of both, just as kittens can, and many do best in a combination. We won't re-tread the whole wet-versus-dry debate here, but you can browse our wet cat food recipes if you're weighing up the options.
Keeping your cat at a healthy weight after the switch
This milestone is the perfect moment to set good lifelong habits, because cat obesity is a genuine and growing problem. In the UK, an estimated 43% of cats are overweight or obese, yet most owners don't know their cat's body condition score (PDSA, 2024).
Body condition scoring sounds clinical, but it's really just a simple hands-on check of your cat's shape. A few things to do regularly:
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Feel along their ribs. You should be able to feel them easily without pressing hard, a bit like the back of your hand
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Look down from above. There should be a gentle tuck in at the waist, not a straight or bulging line
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Weigh out daily portions rather than topping up the bowl by eye
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Try a puzzle feeder or split meals across the day, which suits a cat's natural grazing and gives them something to do
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Have your vet check their weight at routine visits
Activity matters too. Indoor cats tend to burn less than outdoor cats who roam and hunt, so portion sizes may need to reflect your cat's lifestyle. If the scales are heading the wrong way, our slimming cat food can help, ideally alongside a chat with your vet.
Common mistakes when switching
A few easy traps to sidestep:
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Switching too fast. Rushing the change is the number one cause of a poorly tummy. Take the full week or two.
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Switching a large breed too early. Maine Coons and other big breeds are often still growing at 12 months, so check before you swap.
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Leaving a neutered adult on kitten food. Those extra growth calories pile on weight once growing is done.
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Free-feeding with no portion control. A constantly topped-up bowl makes it very hard to spot creeping weight gain.
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Changing brands abruptly. Even between adult foods, a sudden switch can unsettle digestion. Always transition gradually.
The bottom line
For most cats, around 12 months is the moment to move from kitten to adult food, a little later for the big, slow-growing breeds. Make the change gradually over a week or two, keep an eye on their shape as their energy needs settle, and let your vet guide you if you're unsure. Get this milestone right and you're setting your cat up for a healthy, happy adulthood, with extra love and care in every bowl.
When you're ready, explore our adult cat food recipes, made with natural ingredients and no artificial nasties.
FAQs
At what age is a cat an adult?
Most cats are considered adults at around 12 months, which is when they've usually finished growing. Larger breeds mature more slowly and may not reach full adult size until 18 months to two years.
Can I switch my cat's food before 12 months?
It's usually best to wait until growth is finished, as kitten food provides the extra energy and nutrients younger cats need. If you have a specific reason to switch early, check with your vet first.
What happens if an adult cat keeps eating kitten food?
Kitten food is calorie-dense for growth, so a fully grown, especially neutered, cat eating it tends to gain weight over time. It won't cause immediate harm, but it's not ideal as a long-term diet.
How long should the cat food transition take?
Around one to two weeks. Start with a little new food mixed into the old, and gradually increase the new food while reducing the old, slowing down if you notice any tummy upset.
Do large breeds switch later?
Often, yes. Breeds like Maine Coons, Ragdolls and Norwegian Forest cats keep growing past their first birthday, so they may stay on kitten food until around 18 months to two years. Your vet can advise.
Should I change my cat's food after neutering?
Neutering lowers your cat's energy needs, so it's a sensible time to review portions and, once growth is complete, move to an adult or neutered-cat recipe. Keep an eye on their weight in the weeks afterwards.
Can I mix kitten and adult food during the switch?
Yes, and you should. Gradually mixing the two over a week or two is exactly how to transition safely and avoid an upset stomach.
What if my cat refuses the new food?
Go slower. Offer a small amount of the new food in a separate dish next to their usual bowl so they can explore it without going hungry, and increase it gradually once they're tucking in. If they keep refusing, speak to your vet.
