Senior dog food (UK): what changes, what's marketing

Most owners are told that a dog turns senior at seven and needs a different food overnight. The advice I trust says something quieter: PDSA doesn’t say senior food is mandatory. It says to feed “a good quality diet that suits their life stage”. The label is the part you can check, so that’s where I started.

This guide is for owners of dogs from about seven years old, and for anyone about to pay extra for a bag with “senior” on it. I have not tested any food. Prices and figures come from zooplus pages I opened in October 2026.

The short answer

For a healthy older dog, “senior” food is an option, not a rule. What matters is the dog in front of you: weight, appetite, teeth and energy. PDSA says the best time to switch is when a dog reaches the senior age range, but “it’s never too late to switch”. If your dog is a good weight and eats well on a complete adult food, you aren’t failing it by waiting.

When is a dog senior?

Roughly seven, but it moves with size. PDSA says “about seven years old” and notes it can vary by breed, size and health. Purina UK gives five to six for large breeds and around nine for small ones, which is a manufacturer’s view. A ten-year-old Chihuahua and a six-year-old Great Dane can both be “senior” for different reasons.

What actually changes in the bowl

Fewer calories. Both PDSA and Purina say older dogs usually need less energy because they slow down, and that senior foods tend to have fewer calories. PDSA’s warning is the useful part: weight creeps on unnoticed, so check your dog’s body condition regularly.

Protein you can digest. PDSA says senior food usually has high-quality protein that is easier to digest and helps maintain muscle, and that older digestive systems can struggle with some proteins. Purina says senior foods “typically offer a higher protein content”. Hold on to that last claim, because the labels below don’t all agree with it.

Softer food, if teeth are sore. PDSA suggests wet food or pouches for dogs with sore teeth or gums. That is a reason to change the format, not necessarily the brand.

Smaller, more frequent meals. Purina notes that some older dogs prefer smaller portions more often. The pack guide is a starting point only. Adjust to what the scales and your dog’s waistline say.

More fibre, antioxidants and fatty acids. PDSA’s list of what senior food often contains also includes more fibre for digestion, antioxidants for the immune system and fatty acids for skin and coat. Those are things to compare on the label. A word on the front of the bag is not the same as a figure on the back.

What the labels show

I opened the product pages for one adult and one senior food from the same brand, then added the other senior foods on the zooplus senior list. None of the pages gave calories, so I can’t tell you which has fewer. What they did give is crude protein and fat, plus price per kg.

Food	Size	Price per kg	Crude protein	Fat
Arden Grange Daily 1+ Adult, Fresh Chicken & Rice	12kg, £40.99	£3.42	25.0%	15.0%
Arden Grange Daily 7+ Senior, Fresh Chicken & Rice	12kg, £42.99	£3.58	22.0%	12.0%
Hill’s Science Plan Mature Adult 7+ Medium, Chicken	14kg, £51.99	£3.71	17.5%	13.3%
Hill’s Science Plan Mature Adult 6+ Large, Chicken	14kg, £51.99	£3.71	17.7%	14.3%
IAMS Advanced Nutrition Senior Large Dog 7+, Chicken	12kg, £28.99	£2.42	27.0%	12.0%

Prices from zooplus, 29 October 2026; IAMS rechecked on 2 November 2026, after the earlier listing was withdrawn. Hill’s also showed a lower autoship price of £44.19 on both 14kg bags.

Look at the Arden Grange rows. The senior food has less protein than the adult one: 22.0% against 25.0%, and 12.0% fat against 15.0%. That fits “fewer calories”, though I can’t prove it without the energy figure. It does not fit “higher protein for muscle”. So “senior” on the front tells you the dog’s age band, not the nutrient profile. Two foods called senior can differ a lot, and a senior food can sit below its own adult version.

The IAMS senior goes the other way: 27.0% protein and 12.0% fat, more protein than either Arden Grange food. At £2.42 per kg it’s also the cheapest on the page. Same word on the front, opposite protein story on the back.

The joint claims

Look for words like “joint support” and “mobility”. Arden Grange’s senior page says it has “increased levels of glucosamine, chondroitin, and MSM”. Its adult page also lists glucosamine, MSM and chondroitin sulphate for mobility. Hill’s Mature lists pork cartilage (a source of chondroitin sulphate) and crustacean hydrolysate (a source of glucosamine) in the ingredients but makes no explicit joint claim on the page I read. The IAMS large-breed senior lists “glucosamine from animal tissues” at 0.045%. The page gives the percentage and says nothing about what that amount does, so neither can I.

PDSA lists joint support nutrients among features common in senior food, but its article gives no evidence for the benefit. What it recommends for joints is plain: supportive beds, ramps and non-slip mats. If you’re weighing a separate chew or powder, the joint supplements guide goes through what the evidence does and doesn’t show. For the bed side, see dog beds that suit an older dog.

The cost of “senior”

Within one brand the premium can be small. Arden Grange’s senior is £2 more than its adult for 12kg, about 16p per kg or 5%. Across brands the spread is bigger than any age premium: Hill’s at £3.71 per kg is 13p above the Arden Grange senior, while the IAMS senior is about a third cheaper per kg than either. None of those gaps maps to a benefit I could verify from the pages. The extra £2 on Arden Grange is a small bet. A jump to a food at half as much again as the IAMS price per kg is a bigger one, and it’s worth asking your vet what it would buy your particular dog. If you’re feeding a large dog, work out the yearly cost before you commit; the weekly cost guide shows how to do the sum.

Weight is the bigger lever

The number that should worry you most is not on the bag. PDSA’s PAW Report says veterinary professionals estimate that 46% of dogs are overweight or obese, and PDSA notes that in older pets the gain creeps on slowly, so owners often miss it. Most of what a senior food does for a healthy dog is cut calories for a dog that moves less.

You can do a lot of that without a new bag. PDSA’s own list starts with exercise that suits the dog, such as shorter walks more often, and then feeding the right amount, which it says may mean you “cut out extra treats or swap to a more suitable food”. Note the order: treats come before the food swap. It also suggests checking body condition every week, so a change shows up early.

Weight loss matters just as much. PDSA says to speak to your vet if a pet loses weight rapidly, or loses a lot and looks underweight, without a change in diet. A senior food is the wrong answer to that.

How to switch

PDSA says to mix the new food in gradually over 7 to 10 days, because sudden changes can upset digestion. Purina suggests following the pack’s feeding guide at first. Weigh the portions for the first month, and look at the waist and ribs every couple of weeks rather than trusting the number on the bag.

Who should skip this

Dogs at a good weight, eating well on a complete adult food. Nothing in what I read says a healthy seven-year-old must change. If the label, the price and your dog all suit the current food, keep it.

Dogs that are losing weight, eating less, drinking more or chewing awkwardly. PDSA says to speak to your vet if your dog loses weight rapidly or you notice changes in coat, appetite or chewing, or bad breath or bleeding gums. Those are reasons for an appointment, and a different bag could hide them.

Dogs on a veterinary diet, or with a condition or medication. Your vet picks the food. The shelf version of “senior” is not a substitute.

Dogs that need a calorie cut. PDSA says obesity can raise the risk of fatty lumps. If your dog is overweight, a senior food alone may not be enough. Ask the vet about a plan, and look at the treats you give, which add up faster in a less active dog.

What I would not spend extra on

“Senior” as a premium. Check protein, fat and price per kg, and compare with the adult version.

A supplement on top of a food that already lists joint ingredients. You may be paying twice for the same thing; this guide explains why more isn’t automatically better.

A bigger bag than the dog will finish. Older dogs often eat less, and open kibble goes stale.

What to do next

• Dog joint supplements: what the evidence says covers the claim that sits behind most “senior” marketing.
• Dog food cost per week turns price per kg into a weekly figure so you can compare foods fairly.

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Prices, protein and fat figures and ingredients are from zooplus product pages opened on 29 October 2026 (IAMS rechecked on 2 November 2026), and change often. Product claims are the makers’. Advice is from PDSA’s “A guide to senior pet food and feeding your ageing pet” and Purina UK’s “How to feed your senior dog”. I did not find a page on senior feeding from Blue Cross or Dogs Trust, and the Hill’s adult page would not load, so there is no Hill’s adult comparison. None of the pages gave calories. I have not tested any of these foods. Nothing here is veterinary advice — if your dog is unwell, losing weight or has a changed appetite, speak to your vet. Talk to your vet before changing the food of a dog with an illness or on medication.