At What Age Is a Chihuahua a Senior Dog?

Reviewed by Prof. Dr. Kris Angkanaporn, veterinary nutrition advisor to HEH PAWS.

The short answer

A Chihuahua can be considered a senior from anywhere between nine and twelve.

We will not pretend that is anything but a wide window. The reason for it is more interesting than a single figure would suggest.

Why there are two answers

There is no arguing with the rule. The American Animal Hospital Association defines senior as the final 25 percent of an estimated lifespan. The variable is what you put into that equation.

The breed pages are the numbers most people know, though neither source puts a dataset behind them. In fact the AKC's own pages are at odds; one will have you at 14 to 16 and another at 15 to 17.

The 2024 study in Scientific Reports examined 584,734 UK dogs, including 3,848 Chihuahua deaths, and arrived at a median of 11.8 years. It is the only figure with a proper denominator behind it.

There is a third number, around eight, from a 2016 UK veterinary study. Do not make that your guide for lifespan.

The authors themselves will tell you it was a median age at death from 102 cases in a very young, fast-growing population, so the figure is pulled down for reasons unrelated to how long a Chihuahua is capable of living.

Our advice is to plan from nine, hope for twelve, and keep an eye on things from eight.

What changes, and in what order

The data on the breed is where you find the real utility. A 2016 study of 11,647 Chihuahuas under UK care broke down findings by age band.

Figures are the share of dogs in each age band with that finding recorded during one year. Denominators were 1,918 dogs under two, 2,988 aged two to seven, and 664 over seven.

The teeth move first

Periodontal disease is already the most common diagnosis in the two to seven bracket at 16.7 percent, well ahead of anything else, and it reaches 34 percent after seven.

That is not just a small-dog stereotype. A 2021 study of 22,333 UK dogs found Chihuahuas carried roughly twice the odds of diagnosed periodontal disease compared with a crossbred.

The same study found that dogs under 10 kg, as a weight class, carried around three times the odds of dogs in the 30 to 40 kg range.

The heart arrives later, and in a hurry

Murmurs sit under one percent in middle age before they leap past twelve percent after seven, a near fourteenfold change across one boundary.

The median age for a first recorded murmur is 8.9 years, and 9.1 for chronic heart disease.

Teeth and weight first. Heart later, and quickly.

One thing that is not an aging sign

As for the slipping kneecap, the association is real. A study of 210,824 UK dogs found a 4.9 percent prevalence in Chihuahuas against 1.2 percent in crossbreds.

But the data shows it is not an indicator of age. It is largely congenital and holds steady across all age bands.

Should you see a skip in the back leg, have a word with your vet, but do not read too much into it as a sign of aging.

What Chihuahuas change first

Often it is the breath, the earliest and most easily overlooked sign. The rest are small enough to pass for nothing in particular.

• Chewing on one side, or dropping food.
• Reluctance to have the muzzle handled.
• A run-up to a jump the dog would once have taken from a standstill.
• Sleeping off more hours, and in a deeper way.
• Making a beeline for warm places.
• Nails left to grow because the dog is not wearing them down as before.
• A cough on the collar or after some exertion. It costs nothing to mention and can matter a great deal.

What to do from eight

1. Have your vet run a baseline blood panel while the dog is in good health, and ask them to give the heart a thorough listen. For this breed, that record is the one you will want to compare against later.
2. Book an appointment to have the mouth examined. By the numbers, it is the highest-value item on this list for a Chihuahua.
3. Move to twice-yearly visits. A year is a long time in the later life of a small dog.
4. Weigh the dog every month. On a three kilo animal, 300 grams is ten percent and you would not see it with the eye.
5. Keep the nails trimmed. Overgrowth alters how a small dog stands, and that puts a different strain on the joints above.
6. Mention any cough rather than letting it pass.

So when is your Chihuahua a senior?

The breed pages put it at about eleven. The only measured dataset has it at nine.

That is reason enough to start paying attention at eight and not quibble over the figure.

Frequently asked questions

How long do Chihuahuas live?

You will see 14 to 16 years on the breed pages. The largest study with actual data gives a median of 11.8. One can show its working and the other cannot, though neither is entirely wrong.

Is ten old for a Chihuahua?

If you go by the measured figure, a ten-year-old is already a senior. By the breed pages, not quite. In either case it is an age to be seeing the vet twice a year.

Do Chihuahuas really live to twenty?

Some individual dogs have, but those are record holders. There is no dataset to support twenty as an expectation.

Why do Chihuahuas have such bad teeth?

A small mouth has to hold the same number of teeth as a large dog's. Dogs under 10 kg carry around three times the odds of a periodontal diagnosis compared with dogs in the 30 to 40 kg range.

My Chihuahua's back leg skips now and then. Is that age?

Unlikely. Slipping kneecaps are a breed trait and usually present from early on. It is worth putting to your vet, but it is not a sign of aging.

What is the most common cause of death in Chihuahuas?

In the UK study, 18.8 percent of the 80 deaths where a cause was noted were due to heart disease. The sample is small, so take the ranking as indicative rather than precise.

My Chihuahua is already ten or eleven. Is it too late to start?

No. Everything here is worthwhile at any adult age. The earlier years give you the most return on it, but they are not the only time it matters.

Sources

1. McMillan KM et al., 2024. Longevity of companion dog breeds: those at risk from early death. Scientific Reports 14:531. 3,848 Chihuahua deaths out of 584,734 dogs.
2. O'Neill DG et al., 2020. Demography and commonly recorded clinical conditions of Chihuahuas under primary veterinary care in the UK in 2016. BMC Veterinary Research 16:42. 11,647 Chihuahuas; 5,660 records reviewed; 102 deaths, 80 with a recorded cause.
3. O'Neill DG et al., 2021. Periodontal disease in dogs under primary veterinary care in the UK. Journal of Small Animal Practice 62(12):1051-1061. Random sample of 22,333 dogs.
4. O'Neill DG et al., 2016. Patellar luxation in dogs attending primary-care veterinary practices in England. Canine Genetics and Epidemiology 3:4. 210,824 dogs.
5. AAHA, Defining the Senior Patient, 2023 AAHA Senior Care Guidelines for Dogs and Cats. aaha.org
6. American Kennel Club, Chihuahua breed page and Is Your Dog a Senior? akc.org
7. PetMD, Chihuahua breed page. petmd.com