When Is a Dog Considered a Senior?

Updated on July 9, 2019
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Adrienne is a certified dog trainer, former veterinary assistant, and the author of "Brain Training for Dogs."

If you are wondering, "When is my dog considered a senior?," you may be expecting to find an exact age that would put your best friend in the "golden ager club." With dogs, things can get quite complicated when it comes to the aging process.

First of all, if you are trying to figure out how old your dog is in human years, forget about the old, "1 human year equals 7 dog years." This method is inaccurate. Consider this: If Rover is a 1-year-old dog, he would be a 7-year-old child (in human years). Professor of psychology, Stanley Coren, points out one major flaw in this equation. A dog at the age of one is already capable of reproducing, while a 7-year-old child is obviously not! On top of that, this equation fails to keep in mind the great individual variability pertaining to the aging process across different breeds.

Here's the thing: Even though you may bake a cake for your dog every year on his birthday, there's really no official age where dogs are branded with a senior label. After all, dogs are in many ways just like people—they all seem to age at a different pace. All dogs get old eventually, there is ultimately no way out of that, but the rate at which this happens tends to vary widely from one individual to another.

To further complicate things, consider the fact that dogs come in a tremendous range of genetic and phenotypic variability. Indeed, with nearly 400 pure breeds, dogs are the most diverse type of mammals on earth ranging from different shapes, colors, and sizes.

Size though (more than breed), has been found to be the main factor that affects a dog's lifespan. Small dogs are known to age much slower than larger ones. Interestingly, this goes against the rate of living theory which postulates that a shorter lifespan is associated with small size. This theory is based on some evidence which proves that small creatures with faster oxygen metabolism (faster heartbeats) die younger. For instance, small birds or mice live much shorter lifespans than elephants.

However valid this theory may seem, while it does point out some differences in the lifespan between different species, it cannot explain what determines lifespan within species. It would be interesting, therefore, knowing what exactly triggers a small dog to live much longer than a large or giant dog. Until now, there doesn't seem to be any concrete evidence other than some hypothesis generated from a study that would require further investigation.

In any case, does the lack of an age-specific boundary line when it comes to a dog becoming senior mean that it's impossible determining when a dog is considered senior? Well, the good news is that, based on your dog's size and specific weight, it is possible to obtain some rough estimates. Below is a table with some estimates.

At What Age Is My Dog Considered a Senior?

(click column header to sort results)
Dog's Weight  
Age considered senior  
Breed Examples  
15 pounds or less
Chihuahua, Pomeranian, Yorkie
Between 16 and 50 pounds
Border collie, beagle, dachshund
Between 51 and 80 pounds
Boxer, Golden retriever, greyhound
More than 80 pounds
Great dane, mastiff, Irish wolfhound
Source: The Living Well Guide for Senior Dogs, Diane Morgan , Wayne Hunthausen DVM

Senior Dogs: An Age of Changes

As dog owners, we all wish our dogs would stay puppies forever, but dogs grow and soon become adults and then seniors in what feels like the blink of an eye. As in humans, there are many changes that will take place in your dog's senior years.

Some changes are quite noticeable. For instance, you may notice that your dog's muzzle will start turning grey, or they may show some sensory decline and possible cognitive changes. However, changes may occur gradually and dogs are instinctively good at hiding any signs of pain or vulnerability. There are also changes taking place internally.

For instance, within the cardiovascular system, heart issues among senior dogs are common. In particular, degenerative valve disease and congestive heart failure. Senior dogs are also more prone to digestive issues. The pancreas may no longer secrete digestive enzymes as it used to, leading to cases of pancreatitis. The colon may slow down leading to constipation especially in dogs who don't drink enough and don't exercise.

Immunity lowers in senior dogs making infections more likely to happen. The skin loses elasticity and the coat may start looking dull. You may also notice a higher rate of cysts, warts, and lipomas (fatty lumps) growing on or under the skin. The nails thicken too, making them more difficult to trim. Loss of muscle mass may be noticeable in the hind legs. Less cartilage causes the bones to scrape against each other causing the onset of arthritis. Advanced periodontal disease may cause bad breath and eventual tooth loss. Changes in the brain due to aging may cause cognitive disorders leading to disrupted sleep, loss of house training, barking, and separation anxiety.

Aging also causes senior dogs to become more prone to endocrine conditions such as diabetes and Cushing's disease. Elasticity in the lungs decreases, which makes senior dogs more prone to become exercise intolerant. As the organs age, the chances of heart failure, kidney failure, and liver failure heighten.

The Importance of Senior Wellness Exams

It's important to schedule routine wellness exams to assess health and detect any problems in your senior dog before they become more widespread and more difficult to treat. Some vets suggest these exams now twice a year.

At your senior dog's examination, your vet will likely conduct a physical exam to check for any abnormalities and he or she may also suggest a variety of exams. A senior blood panel, in particular, may be an option that will help screen for age-related changes and diseases.The senior blood panel may include a complete blood count, chemistry profile, thyroid hormone testing and urinalysis.

The blood chemistry test can help screen for diabetes, and liver and kidney failure. The complete blood count (CBC) takes a look at red blood cells, white blood cells and more and can detect the presence of anemia or infection. Thyroid hormone levels are often tested to screen for low thyroid levels. The urinalysis involves getting urine tested so to check the dog's kidney function and presence of urinary tract infections.

Further tests may include chest X-rays to check the heart and lungs. X-rays of bones to rule out bone cancer in limping senior dogs. Fine needle aspirations of any suspicious lumps and bumps to rule out certain types of cancer. Of course, many other tests such as high blood pressure tests, electrocardiograms, ultrasounds, and other tests may be carried out depending on the vet's physical exam findings at the time of the exam.

On top of having your senior dog see the vet for routine check-ups, have your senior dog seen if you notice any of the following changes:

  • increased thirst and urination
  • accidents around the house
  • vomiting and/or diarrhea
  • constipation
  • bad breath
  • appetite changes
  • increased panting
  • exercise intolerance
  • coughing
  • weakness
  • the presence of lumps or suspicious bumps
  • changes in behavior
  • orthopedic problems
  • weight gain or weight loss

When feasible, it's always best though to catch things early. As the saying goes, "an ounce of prevention is worth a pound of cure."

Preventive veterinary care can add years and quality of life to your older pet. We recommend twice-yearly checkups for seniors.

— Dr. Foster and Smith


  • The Living Well Guide for Senior Dogs: Everything You Need to Know for a Happy & Healthy Companion by Diane Morgan, TFH Publications; 1 edition (October 1, 2007)
  • The Size–Life Span Trade-Off Decomposed: Why Large Dogs Die Young, Cornelia Kraus, Samuel Pavard and Daniel E. L. PromislowThe American NaturalistVol. 181, No. 4 (April 2013), pp. 492-505

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2018 Adrienne Farricelli


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    • Suhail and my dog profile image

      Suhail Zubaid aka Clark Kent 

      2 years ago from Mississauga, ON

      This is a very informative article, Adrienne!

      I agree with you that different breeds of dogs age differently. Even among large sized dogs, while Irish wolfhounds and great Danes tend to have shorter lives, livestock guardian dogs tend to live for much longer duration.

      I think instead of any charts, one should look for signs of seniority that you have outlined in this article.


      Suhail and my dog.


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