If your dog is suddenly quiet or your cat is hiding and not responding normally, you might find yourself asking:

“Is my pet just tired… or is this something serious?”

Lethargy in dogs and cats is one of the most common reasons pet owners contact their vet. While sometimes it’s harmless, it can also be an early warning sign of illness.

Here’s what you need to know about lethargy in pets, when to call the vet, and what you can safely monitor at home.

What Is Lethargy in Pets?

Lethargy is more than normal tiredness.

A lethargic dog or cat may:

• Be unusually quiet or withdrawn
• Show little interest in food, play, or interaction
• Sleep more than usual and be difficult to wake
• Move slowly or seem weak
• Appear mentally dull or less responsive

A tired pet still responds to excitement — like dinner being served or a walk.

A lethargic pet often does not.

That difference is important.

Why is My Dog or Cat Lethargic?

Lethargy is a symptom — not a diagnosis. It tells us something may be happening inside the body.

Common Causes of Lethargy in Dogs and Cats

Mild causes:

• Recent vaccination
• Minor stomach upset
• Temporary stress
• Overexertion

More serious causes:

• Infection
• Pain (including dental pain)
• Pancreatitis
• Heatstroke
• Tick paralysis (especially in Australia)
• Heart disease
• Internal bleeding
• Toxin ingestion
• Diabetes
• Kidney disease

Because the causes range from mild to life-threatening, persistent lethargy should always be assessed.

Lethargic Dog: When to Call the Vet

You should contact your vet if your dog:

• Is lethargic for more than 24 hours
• Refuses food or water
• Has vomiting or diarrhoea
• Has pale, white, blue or grey gums
• Is breathing heavily or rapidly
• Seems weak, wobbly or collapses
• May have been exposed to ticks or toxins

In Australia, tick paralysis can cause sudden lethargy and weakness — especially during tick season. Early treatment is critical.

Lethargic Cat: Is It Serious?

Cats are very good at hiding illness. If your cat is lethargic and not eating, this is more concerning than in dogs.

Call your vet promptly if your cat:

• Stops eating for more than 12–24 hours
• Hides excessively
• Shows changes in breathing
• Has vomiting or diarrhoea
• Appears weak or unsteady

In cats, even short periods of not eating can lead to serious complications such as fatty liver disease.

What Can You Check at Home?

If your pet seems lethargic but stable, you can:

1. Check Gum Colour

Healthy gums should be pink.
Pale, white, grey or blue gums are an emergency.

2. Monitor Eating and Drinking

Offer small amounts of fresh water.
Do not force-feed.

3. Look for Signs of Pain

Reluctance to move, sensitivity when touched, hiding, or unusual posture.

4. Consider Possible Toxin Exposure

Chocolate, human medications, compost, plants, or spoiled food.

5. Keep Them Calm and Comfortable

A quiet, cool environment is best.

Do not give human medications unless directed by your veterinarian. Many are toxic to pets.

Is Lethargy in Pets an Emergency?

It can be. Lethargy combined with:

• Collapse
• Difficulty breathing
• Pale gums
• Severe vomiting
• Abdominal swelling
• Suspected tick paralysis

… should be treated as urgent.

If your pet simply seems mildly quiet but is still eating, drinking, and responsive, it may not be an emergency — but if it persists, it should still be checked.

The Bottom Line

Lethargy is one of the body’s earliest warning signs.Sometimes it resolves quickly.
Sometimes it signals something serious.
If your dog or cat is not acting like themselves, trust your instincts and contact your veterinarian. Early intervention can make all the difference.

If you are ever unsure, it is always safer to call and ask.

Book an Appointment Today