Just like us, all dogs need to rest – especially after exercise and when they're very young or old. But if your dog lacks energy and enthusiasm for their normal activities and has other symptoms too, it could point to a more serious health problem.
Lethargy is a possible sign of lots of issues, though, making it tricky to pinpoint the exact cause without proper examination. This means it's important to know how the difference between normal tiredness and severe lethargy and when you should take your pet to a vet.
Our research shows that almost half of dog owners worry about their pet's health more than their own. So, if you're concerned that your dog is lethargic and not themselves, read up on the signs and possible causes below and what to do next.
So, why is your dog so tired all of a sudden? Thankfully there are plenty of perfectly normal reasons why your dog might be tired or sleep a lot.
For example, if you take them on long walks or play with them a lot, they might sleep soundly for a few hours afterwards – especially in hotter weather. Or if they go away with different carers or to a kennel and are on alert more than usual, sometimes they'll get home and crash.
Like humans, most dogs need more sleep when they're very young. While a typical adult dog sleeps for 10-12 hours a day on average, puppies need more rest to support their development.
This can be up to 20 hours a day initially, before gradually decreasing with age. Senior dogs, meanwhile, can need more nap time than younger adult dogs, particularly after exercise and play.
In summary, there might be lots of plausible reasons for your dog getting tired easily or sleeping a lot. But if your dog is always tired or more tired than usual and you can't easily explain it, they might be struggling with lethargy - and it could need some extra investigation.
So how can you tell if your dog is lethargic or just tired? Crucially, lethargy in dogs is a little different to regular sleepiness.
A normal tired dog should be easy to rouse with the sound of their name or the jingle of their leash or food bowl. They'll act alert and engaged when they're awake too. But if your dog is unable or unwilling to get up, moves slowly and seems different in themselves, it can be a sign that something's not right.
A lethargic dog may lack their normal level of interest in walking, treats or their favourite toy, for example. A severely lethargic dog will be only partially alert too, as if they aren't properly seeing or hearing what's going on around them.
If your normally energetic dog seems lethargic, here's how to quickly tell the difference between tiredness and something potentially more serious.
| A tired dog... | A lethargic dog.. |
|---|---|
| Is sleepy some of the time | Sleeps excessively |
| Is sometimes disinterested in some normal activities like walking and play | Is always disinterested in most normal activities |
| Responds to stimulation (noises, movement and contact) | Doesn't respond to stimulation |
| Mostly acts like themselves | Isn't acting like themselves |
According to our research, sleeping more than usual is the one behaviour that owners are most likely to link to old age rather than health problems. But sudden lethargy is a common sign of illness in dogs. The problem is that lots of different issues can be to blame, making it important to gauge how tired or lethargic they are and whether they have other symptoms too.
If your dog seems mildly or moderately lethargic with no other symptoms, they might have simply overdone it on a walk or in the heat. They might be sleepy for a while but then act largely normal soon after waking, showing interest in their favourite treat, for example. On the other hand, it could be severe lethargy if your dog's tired all the time with no obvious explanation and nothing gets their attention. You may have more cause for concern if they show other symptoms too, such as if your dog is lethargic and breathing heavily, panting or wobbly.
In these cases, you should take your dog to see your vet or an emergency vet right away.
It's nearly impossible to provide a complete list of possible reasons for lethargy because so many medical conditions can cause it. General triggers for your dog being unusually tired and listless include disease, medication, poisoning and pain.
Causes also vary based on age and can be identified by other symptoms, as we've outlined below. But if you're at all unsure about the nature or severity of their issues, it's best to speak to your vet for clarity.
You may notice a change in your dog's energy and sociability following a major change such as losing an owner, a new person moving into their home, or moving to a new home themselves.
If your dog seems lethargic and depressed following a major change, a week or two of love and care should get them back to their best.
Lethargy and shaking commonly indicate that your dog is in pain and may be intentionally limiting their movement to reduce it. These symptoms can also point to nerve or gastrointestinal issues, as well as soft tissue injuries and fever. Whatever the case, it can be worth speaking to your vet to help them get comfortable sooner.
Laboured breathing can be a sign of more serious issues such as heart failure, fluid in the lungs, severe pain or a blocked airway, so it's important to see a vet right away.
It's worth noting that laboured breathing is different to panting, usually shown by them moving their bellies up and down quickly and with force
Lethargy and drooling or vomiting usually suggests that your dog has eaten something toxic or swallowed an object that's got stuck. While it's not uncommon for dogs to be sick occasionally, it's worth seeing a vet if their nausea seems severe enough to cause lethargy.
Cushing's is a lesser-known syndrome that can impact the health and vitality of middle-aged and older dogs. It's caused when they produce too much cortisol, a hormone that helps regulate their metabolism. Cushing's can impact your dog's organs and ability to regulate itself, but thankfully treatment is usually successful when it's caught and treated correctly.
Read more about what Cushing's syndrome is.
Lethargy is one of several common symptoms of Cushing's syndrome in dogs, with others to look out for including:
James Walker, Technical Services Manager at Dechra advises "Many of these symptoms are seen as normal signs of old age, so Cushing's may be misdiagnosed or even not diagnosed at all. But spotting the common signs and speaking to your vet could help you improve your furry friend's quality of life."
If you do decide to speak to a vet about Cushing's, they'll perform a clinical examination and likely some blood and urine tests. Learn more about how Cushing's is diagnosed and treated.
As we've highlighted, there are lots of possible reasons why your dog might seem tired, and many aren't anything serious. Like us, they're often able to sleep off whatever was bothering them.
But if your dog is clearly lethargic and not themselves with no obvious cause, such as intense exercise, it's best to see your vet for a check-up. If your dog is lethargic along with other signs such as laboured breathing, you should visit the emergency vet instead to be safe.
They'll perform a thorough physical examination and ask questions about your dog's behaviour and health record. They may carry out tests and scans to get to the root of the issue and identify the best treatment, helping your dog rediscover their vitality soon.
