Dog weight loss – when should I see a vet?

Updated 2026-09-30 · 1 sources

Based on: PDSA

Book a vet visit

This is not usually an emergency on its own – contact your vet if it lasts, gets worse or your dog seems unwell in any other way. Weight loss in dogs has many different causes.

When to contact a vet What to do now

Contact a vet if you see any of this

Sudden weight loss
Weight loss with no obvious cause

What you can do now

Contact your vet.
Note when it started, how often it happens and what else you see.
Take a photo or short video to show the vet.
Keep fresh water available.
Let your dog rest somewhere calm.

Don't

Do not give any human medicine.
Do not wait if it gets worse.

What it can mean

Weight loss can happen when a dog is eating less than usual.^[1] It can also mean your dog is not getting enough food or calories for their size, or is doing more exercise than usual.^[1] It is usually only a concern if it happens suddenly or when there is not an obvious cause.^[1]

Other signs that can come with it

Low energy
Drinking more or less than usual
Peeing more than usual
Decreased appetite
Increased appetite
Vomiting
Diarrhoea
Panting or struggling to breathe

Possible causes

Worms
Dental disease
Stress
Lack of food
Kidney disease
Diabetes
Other illness
Eating less than usual
Having food eaten by another pet
Doing more exercise than usual

What the experts say

“Lethargy (low energy) ; Drinking more or less than usual ; Peeing more than usual ; Decreased appetite ; Increased appetite ; Vomiting ; Diarrhoea ; Panting or struggling to breathe ; Coughing”
— PDSA [1]

If your pet is struggling to breathe, has collapsed, is having a seizure or can't stand up: go to the nearest vet now.

Not sure how serious it is?

OkPaw asks a few quick questions about your pet and tells you in 30 seconds whether it can wait. Free on Google Play for Android.

OkPaw is on Android now – an iPhone version is on its way.

Common questions

What can weight loss in dogs mean?

Weight loss in dogs has many different causes.^[1]

When is weight loss more concerning?

It is usually only a concern if it happens suddenly or when there is not an obvious cause.^[1]

What other signs should I tell my vet about?

Tell your vet about vomiting, diarrhoea, low energy, or changes in your dog’s appetite and thirst.^[1]

Sources

PDSA

How this page was made: written with the help of AI from the sources below, then checked claim by claim against those sources. Urgency levels follow OkPaw’s fixed safety rules. It is guidance, not a diagnosis. How we write our pages

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