SYMPTOM
Sleeping more than usual
The dog or cat spends noticeably longer stretches asleep or dozing, is slower to rouse for meals, greetings, or a walk, and initiates play, exploration, or affection less often than before. Owners often describe it as the animal simply not being themselves during what would normally be an active part of the day.
Degenerative Joint Disease
Osteoarthritis in dogs and arthritis in cats make rising, stretching, and moving around less comfortable, so the animal increasingly chooses rest over activity. Stiffness is often most obvious on rising after a long rest, in dogs it can be worse in cold, damp weather, and cats often show a reluctance to jump.
Chronic Kidney Disease
Reduced kidney function allows waste products to accumulate in the bloodstream, producing a generalised malaise that shows as increased sleep and reduced enthusiasm. Increased thirst and urination are usually the earliest signs, and lethargy tends to follow as the disease progresses. Chronic kidney disease becomes more common with age in both cats and dogs, and it is particularly relevant in older cats.
Endocrine Imbalance
Hypothyroidism in dogs slows the metabolic rate, and lethargy, mental dullness and tiring more easily on walks are among its signs, so the dog can seem to need more sleep. Weight gain without an increase in appetite and a dry coat with excessive shedding often accompany the change.
Cognitive Decline
Canine and feline cognitive dysfunction can alter the sleep-wake cycle itself, so daytime sleep increases while night-time settling becomes less predictable. This pattern tends to build slowly over months in older animals and often accompanies other subtle shifts in orientation or routine.
Anaemia
A falling red blood cell count, whether from immune-mediated destruction or another cause, reduces the oxygen reaching tissues and produces fatigue that owners often read as excess sleepiness. Pale or yellow-tinged gums, weakness and a faster heart rate can accompany it. Immune-mediated haemolytic anaemia can develop slowly or arrive as a sudden severe crisis, and published death rates range from 20% to 75%, depending on how severe the disease is.
Adrenal Insufficiency
Addison's disease in dogs produces a waxing and waning malaise that is easy to mistake for simple tiredness, and in the substantial minority of affected dogs with the atypical form of the disease, routine electrolyte results are normal at diagnosis, although some of these dogs develop electrolyte changes later. Lethargy here can fluctuate rather than build in a straight line, sometimes alongside vague gastrointestinal upset. Some dogs present in an Addisonian crisis, with shock, severe vomiting or diarrhoea and a slow or irregular heart rhythm, which is life-threatening.
Normal Age-Related Change
Many older dogs and cats simply sleep more as part of ordinary ageing, particularly when the extra sleep is stable, unaccompanied by other changes, and the animal remains bright, eats well, and rouses normally when called. A change in routine, activity level, or season can also shift the balance between waking and resting hours without reflecting an underlying process.
Why timing matters
Early observation
Sleep that has increased over hours or days rather than months more often reflects an acute process, such as infection, a pain flare, gastrointestinal upset, a medication effect, internal bleeding, haemolytic anaemia or an Addisonian crisis. Some of these settle as the trigger passes, but a bleeding tumour can cause sudden collapse and death, and haemolytic anaemia and an Addisonian crisis can also be life-threatening. These causes cannot be told apart from simple tiredness at home.
Later presentation
A gradual, long-standing increase in sleep that has built over many weeks or months more often reflects a chronic or degenerative process, such as joint disease, organ decline, or cognitive change, where the sleep pattern is one of several slowly accumulating shifts.
Tracking whether the change appeared abruptly, crept in steadily, or comes and goes in episodes helps separate an acute event, which can be serious, from a chronic process that is likely to continue developing, and this trajectory is often more informative than the sleep increase considered on its own.
Conditions commonly associated
Osteoarthritis in Dogs
Joint pain reduces willingness to move and makes rest the more comfortable option, so affected dogs often sleep more overall.
Arthritis in Cats
Discomfort in the joints, often under-recognised in cats, lowers general activity and increases time spent resting or asleep.
Chronic Kidney Disease in Cats
The buildup of metabolic waste products that accompanies declining kidney function produces a generalised lethargy that owners may notice as increased sleep, usually after a period of increased thirst and urination.
Hypothyroidism in Dogs
A slowed metabolic rate reduces energy levels and increases the amount of sleep a dog appears to need.
Canine Cognitive Dysfunction
Disruption of the normal sleep-wake cycle is a recognised feature, producing more daytime sleep alongside altered night-time settling.
Immune-Mediated Haemolytic Anaemia (IMHA)
A falling red blood cell count reduces oxygen delivery to tissues, producing fatigue that is often read at home as excessive sleepiness.
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Addisons Disease in Dogs
Addison's disease leaves the adrenal glands unable to produce enough cortisol, and in most dogs aldosterone as well, which disrupts energy metabolism and often electrolyte balance, so affected dogs tire more easily and spend more time asleep or resting.
Geriatric Frailty in Dogs
As multiple body systems gradually lose reserve capacity in older dogs, the energy required for normal activity can exceed what the body comfortably supplies, and longer rest periods become the norm. The change in sleep pattern tends to be gradual and may be one of the earlier signs that resilience is declining.
Hepatic Encephalopathy
When toxins that would normally be filtered by the liver accumulate in the bloodstream and reach the brain, they can alter neurological function in ways that include lethargy, reduced responsiveness, and prolonged sleep. The drowsiness often comes and goes, and a high-protein meal can bring on an episode. Severe episodes can progress to collapse, seizures and coma.
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Haemangiosarcoma
Haemangiosarcoma can bleed into the abdomen without any injury, and the lethargy, weakness and reduced appetite this causes can look like extra sleep. A rupture can cause collapse with pale gums and fast heart and breathing rates, and severe bleeding can be fatal.
When to explore further
A sudden shift into unusual sleepiness in a dog or cat that was previously consistently active carries different weight to a gradual drift that has developed over many months.
Increased sleep alongside a change in thirst, urination, appetite, or body weight tends to widen the list of relevant systems beyond simple tiredness.
Pale, white or yellow-tinged gums, fast or laboured breathing, weakness or collapse alongside increased sleep can signal anaemia or internal bleeding, which can be life-threatening and cannot be assessed at home. Restlessness or difficulty settling in one position can point to pain.
Cats in particular tend to reduce visible activity gradually and without obvious complaint, so a cat that has stopped jumping to favourite perches or grooming as often can be showing the same underlying pattern in a quieter form.
A reversal of the normal sleep pattern, where daytime dozing increases but night-time settling becomes more restless or vocal, points towards a different set of possibilities than simple daytime fatigue.
Noting the approximate number of hours spent active versus resting over a few representative days, along with the time of day sleep is heaviest, can add useful context. A short video of the animal rising from rest or moving after a period of sleep can capture stiffness or hesitancy that is easy to miss in the moment, and logging appetite, thirst, and body weight alongside the sleep pattern helps show whether the change is isolated or part of a broader shift.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS