Quick answer: Most dogs can switch to a senior formula at 7 years for large breeds, 8 for medium, and 9 to 10 for small breeds. The key nutritional changes are: slightly lower calories (to prevent weight gain as activity drops), moderate reduction in phosphorus (kidney support), added joint-support nutrients (glucosamine, chondroitin, omega-3 in some formulas), and a softer kibble for easier chewing. The "senior" label is not tightly regulated in the UK, so the formula matters more than the word on the bag. Wet food can help older dogs with dental issues or reduced thirst drive. UK senior dog food ranges from £30 to £80 for a 6 to 12 kg bag.
When to switch to senior food
A general rule by breed size.
- Small breeds (under 10 kg adult weight): switch at 9 to 10 years.
- Medium breeds (10 to 25 kg): switch at 8 to 9 years.
- Large breeds (25 to 40 kg): switch at 7 to 8 years.
- Giant breeds (over 40 kg): switch at 6 to 7 years.
The rule is a starting point. The actual reasons to switch are health-driven: a confirmed diagnosis of arthritis, kidney disease, dental issues, or weight gain. If your dog is 9 and a healthy adult weight, the switch is optional. If your dog is 7 and overweight with stiff joints, the switch is worth doing now.
The switch itself should be gradual. Mix 25% new food with 75% old food for 3 to 4 days, then 50/50 for 3 to 4 days, then 75/25 for 3 to 4 days, then 100% new. A sudden switch upsets the gut.
What changes in a senior formula
A typical senior dog food changes 5 things versus an adult formula.
1. Slightly lower calories. Senior dogs are less active. A 10 to 20% calorie reduction prevents weight gain. This is the single most important change.
2. Moderate reduction in phosphorus. Phosphorus is hard on ageing kidneys. Most senior formulas have ~0.5 to 0.8% phosphorus on a dry-matter basis, down from ~1% in adult food. The change matters for dogs with diagnosed kidney disease; for a healthy senior dog, the effect is small.
3. Added joint-support nutrients. Most senior formulas include glucosamine, chondroitin, or omega-3. The levels are usually low (not therapeutic doses), so the food is supportive, not curative. A senior dog with diagnosed arthritis usually needs a separate joint supplement on top of the food.
4. Softer kibble. Many senior formulas have a softer kibble texture for easier chewing. Important for senior dogs with dental issues. For dogs with significant dental pain, switching to wet food is a bigger win.
5. Higher fibre. Some senior formulas increase fibre to help with digestive regularity. A useful but not essential change.
The "senior" label
The "senior" label on UK dog food is not tightly regulated. The Pet Food Manufacturers' Association (PFMA) has a code of practice but does not require a specific nutritional profile for "senior" food. The label is a marketing category, not a regulatory one.
In practice, a UK senior dog food from a major brand (such as the supermarket own-label, Hill's, Royal Canin, or similar) will be formulated with the 5 changes above. A budget "senior" food from a marketplace seller may be a basic adult formula with a "senior" sticker.
The right approach: read the ingredients list and the analytical constituents (protein, fat, fibre, moisture, phosphorus) rather than trusting the front-of-pack label.
Wet food vs dry food for senior dogs
A practical comparison.
| Factor | Dry kibble | Wet food | |--------|------------|----------| | Dental benefit | Some abrasive benefit (limited) | None, can stick to teeth | | Hydration | Low (8 to 12% moisture) | High (70 to 80% moisture) | | Cost per day | Lower | Higher (2 to 3x) | | Storage | Easy | Open cans need refrigeration | | Palatability for older dogs | Lower if teeth are bad | Higher | | Kidney support | Lower moisture | Better hydration support |
For a senior dog with dental issues, reduced thirst drive, or chronic kidney disease, wet food is often the better choice. The cost is higher, but the hydration benefit is real.
A mixed approach (some wet, some dry) gives the dental benefit of kibble and the hydration benefit of wet. Many UK owners feed a 50/50 mix.
What to look for in a senior dog food
Five things on the label.
- Protein 20 to 30% on a dry-matter basis. Senior dogs need protein for muscle maintenance. Low-protein senior foods (under 18%) are not supported by current evidence unless the dog has severe kidney disease.
- Fat 8 to 15%. Enough for palatability and energy.
- Phosphorus under 1% on a dry-matter basis (lower is better for kidney support).
- Named protein source (chicken, salmon, lamb, turkey) as the first ingredient, not "meat and animal derivatives".
- No artificial colours or flavours. A senior dog does not need them, and some are linked to hyperactivity in older dogs.
UK price ranges in 2026
- Supermarket own-label senior dry food (6 to 12 kg bag): £25 to £40.
- Major brand senior dry food (6 to 12 kg bag): £40 to £70 (Hill's Science Plan, Royal Canin, James Wellbeloved, Burns).
- Premium / veterinary senior dry food: £60 to £90 (specific kidney, joint, or weight formulas).
- Senior wet food (12 x 400g): £25 to £50.
A 12 kg bag of mid-range senior dry food lasts a medium dog about 4 to 6 weeks. The cost is around £1 to £2 per day, comparable to adult food.
Treats and supplements
Senior dogs still need treats for training and dental health. Choose:
- Soft, low-calorie training treats (dried chicken, soft dental chews).
- Joint-support treats with glucosamine and chondroitin. A useful add-on.
- Omega-3 fish oil as a separate supplement. The strongest-evidence joint supplement for dogs.
Avoid:
- Hard chew treats (rawhide, antlers, hard nylon). Senior dogs with dental issues can crack teeth on hard chews.
- High-fat table scraps. A senior dog's metabolism is slower; extra fat is unnecessary.
FAQ
Frequently Asked Questions
When should I switch my dog to senior food?
Generally 7 years for large breeds, 8 for medium, 9 to 10 for small. The actual switch should be health-driven: a confirmed diagnosis of arthritis, kidney disease, dental issues, or weight gain. Switch gradually over 7 to 10 days to avoid gut upset.
What is the difference between adult and senior dog food?
Five main changes: lower calories (10 to 20% less) to prevent weight gain; moderate reduction in phosphorus for kidney support; added joint-support nutrients (glucosamine, chondroitin, omega-3); softer kibble for easier chewing; higher fibre for digestive regularity. The 'senior' label is not tightly regulated in the UK; check the analytical constituents rather than trusting the front-of-pack label.
Should a senior dog eat wet food or dry food?
Wet food is often the better choice for senior dogs with dental issues, reduced thirst drive, or chronic kidney disease, due to higher moisture content. Dry food has limited dental benefit and lower hydration. A mixed approach (some wet, some dry) gives both benefits. Wet food costs 2 to 3 times more per day than dry.
See our senior dog care guide UK for the full picture, and our enrichment guide for slow-feeder and lick-mat options.
Senior dog care guide UK Senior dog joint care UK Senior dog orthopaedic beds UK Enrichment guide Beds guide Complete dog grooming guide