When Is a Dog a Senior? Age by Size and Breed

There is no single age at which a dog becomes a senior. The 2019 AAHA Canine Life Stage Guidelines define senior as the last 25% of the breed’s expected lifespan, which means a Great Dane is a senior at 6 while a Papillon is not one until 11.

Senior age by size

Size	Expected lifespan	Senior from
Toy (under 12 lb)	12–16 years	about 11
Small (12–28 lb)	12–15 years	about 10
Medium (28–55 lb)	10–14 years	about 9
Large (55–100 lb)	9–12 years	about 8
Giant (over 100 lb)	7–10 years	about 6–7

Breed matters more than size where the two disagree. A French Bulldog is small but has one of the shortest life expectancies recorded, so it is a senior before a Border Terrier of the same weight. Use the senior dog age calculator for your breed, or look the breed up in the breed lifespan database.

What changes when a dog becomes a senior

Metabolism slows. Senior dogs need roughly 20% fewer calories than young adults, while protein needs stay the same or rise to protect muscle. Weight creeps up if food stays the same, and every extra pound now loads worn joints.

Diseases of age appear. Arthritis, dental disease, kidney disease, heart valve disease, cognitive decline and cancer all become more common. Most are treatable, and most are treated too late because the early signs are quiet: drinking a little more, slowing on walks, a night of pacing.

A year is a long time. At the pace a senior dog ages, twelve months between check-ups can mean a condition goes from early to advanced. AAHA recommends exams every six months from the senior stage, with bloodwork and a urine test at least yearly.

The senior check-up

Ask your vet for:

• A full physical exam including weight, body condition score and muscle condition score
• Blood pressure (hypertension is common and silent)
• Complete blood count and chemistry panel including kidney values (creatinine, SDMA) and thyroid
• Urinalysis
• Orthopedic exam and a frank conversation about pain
• Dental assessment
• Any breed-specific screening: heart auscultation or echo for breeds with valve or muscle disease, eye exam for breeds prone to glaucoma or retinal disease

Bring a list of small changes you have noticed. Owners see the early signs long before a clinic does.

Next steps

Work through the senior dog checklist, and read about arthritis, the most under-treated condition in older dogs.