When Is a Dog Considered Senior?

Breed size	Senior life stage begins
Small breeds (under 10kg)	Around 10 to 12 years
Medium breeds (10 to 25kg)	Around 8 to 9 years
Large breeds (25 to 45kg)	Around 7 to 8 years
Giant breeds (over 45kg)	Around 5 to 6 years

Key Nutritional Needs in Senior Dogs

Protein

Older dogs often need higher levels of high-quality, digestible protein -- not less protein as was previously believed. Protein supports muscle mass maintenance, which naturally declines with age (sarcopenia). Look for a senior food with a named meat source as the first ingredient and a minimum of 22 to 25% crude protein.

Calories

Many senior dogs become less active, reducing their energy requirements. UK Pet Food reports vets estimate 50% of UK dogs are overweight -- senior dogs are disproportionately represented. Monitor body condition every four to six weeks and reduce portions if weight is creeping up.

Joint Support

Glucosamine and chondroitin are commonly added to senior dog foods to support cartilage health. Omega-3 fatty acids (EPA and DHA) from fish oil have stronger evidence for an anti-inflammatory effect on joints. If your senior dog has diagnosed joint disease, speak to your vet about whether a prescription joint diet or additional supplements are appropriate.

Digestibility

Older dogs can have reduced digestive efficiency. Highly digestible protein sources (chicken, fish, egg) and lower fibre levels support nutrient absorption.

Dental Health

Dental disease is extremely common in older dogs. Regular tooth brushing and dental checks with your vet are more effective than diet alone. Senior-specific foods and dental diets can support but not replace dental care.

When to Switch to Senior Food

There is no single right time. Discuss timing with your vet. Signs a switch may help include weight gain that is hard to manage on adult food portions, reduced energy or muscle condition, changes in coat quality, or digestive changes.