Puppies are naturally full of energy, curiosity, and a seemingly endless appetite.
So when you notice your puppy is lethargic, not eating, and sleeping a lot, it’s easy to worry something’s not right.
While it’s normal for young puppies to nap frequently, a noticeable drop in energy or refusal to eat could indicate illness.
We outline the common causes, what you can do at home, and when your lethargic puppy who’s not eating and sleeping a lot needs to see a vet.
Lethargic Puppy Not Eating and Sleeping a Lot: Why It Happens
When a puppy is lethargic not eating and sleeping a lot, it may be due to normal developmental sleep patterns, stress, minor digestive issues, infections like parvovirus, parasites, or more serious problems like hypoglycemia or congenital illness.
Puppies are fragile and can go downhill quickly, so even mild symptoms deserve close observation.
Normal Sleep vs. Lethargy
Young puppies, especially those under 4 months old, can sleep 16–20 hours a day. That’s perfectly normal! The difference between normal sleep and concerning lethargy lies in behavior when awake.
Concerning signs:
Difficulty waking
Weak movement or stumbling
Lack of interest in food or play
Not responding to sounds or touch
If your puppy seems overly drowsy or “out of it,” you’re right to be concerned—especially if they skip meals or treats.
Lethargic Puppy Not Eating and Sleeping a Lot: Common Causes
Stress or Environmental Changes
Stress from moving to a new home, weaning, or separation from littermates can cause a puppy to sleep more, eat less, and seem withdrawn.
This stress can last a few days but should improve with:
A calm, predictable routine
Gentle handling and reassurance
Familiar toys and a quiet sleep area
If stress is the only cause, your puppy should perk up and resume eating within 24–48 hours.
Intestinal Parasites
Parasites like roundworms, hookworms, or coccidia are extremely common in puppies and can cause fatigue, appetite loss, and digestive upset.
Signs include:
Bloated belly
Soft or runny stools
Weight loss or slow growth
Visible worms in stool
A fecal test at your vet can detect parasites, and deworming medications are typically effective and fast-acting.
Related: My dog is lethargic and not eating (Causes and when to worry)
Parvovirus
Parvo is a serious and often fatal viral infection that affects mostly unvaccinated puppies. If your lethargic puppy isn’t eating and is sleeping excessively, watch closely for early parvo signs.
Symptoms include:
Vomiting or diarrhea (often bloody)
Fever or low temperature
Rapid dehydration
Sudden collapse or weakness
Parvo is an emergency. If you suspect it, contact your vet immediately—early treatment significantly improves survival chances.
Hypoglycemia (Low Blood Sugar)
Small or toy-breed puppies are prone to drops in blood sugar, especially if they miss a meal or are under stress. This can lead to:
Weakness or wobbliness
Lethargy and tremors
Seizures in severe cases
Refusal to eat
Rub a small amount of honey or corn syrup on your puppy’s gums to raise blood sugar temporarily, then get veterinary care right away.
Infection or Fever
Even a minor viral or bacterial infection can cause your puppy to feel tired and lose interest in food. Look for:
Warm ears or nose (fever)
Swollen lymph nodes
Nasal discharge or sneezing
Shivering or chills
Puppies can deteriorate quickly, so a physical exam and bloodwork are key to identifying and treating the underlying cause.
Teething or Minor Digestive Upset
During the teething phase (typically 3–6 months), puppies may temporarily lose their appetite or act more subdued.
You may notice:
Chewing on everything
Red or swollen gums
Slight drooling
Preference for soft food
This should pass in a few days, but contact your vet if your puppy also has vomiting, diarrhea, or extreme tiredness.
Congenital Illness or Genetic Conditions
Some puppies may be born with underlying heart, liver, or neurological issues that affect energy levels, appetite, and growth.
Warning signs:
Not keeping up with littermates
Labored breathing or heart murmurs
Poor weight gain
Persistent fatigue
These conditions require testing like bloodwork, X-rays, or ultrasound. Early diagnosis can lead to supportive treatment and a better quality of life.
What to Do If Your Puppy Is Lethargic, Not Eating, and Sleeping a Lot
Here are some steps you can take right away:
Check their temperature – Normal rectal temperature for puppies is 101–102.5°F (38.3–39.2°C).
Offer soft, warm food – Try bland options like boiled chicken or puppy-safe baby food.
Encourage hydration – Offer water or puppy-safe electrolyte solutions.
Check gums – Pale gums can indicate anemia or shock.
Limit activity and stimulation – Let your puppy rest in a warm, quiet area.
If your puppy shows no improvement in 12–24 hours, contact your vet promptly.
When to Call or Visit Your Vet
Call your vet immediately if:
Your puppy hasn’t eaten or drunk in over 12 hours
Vomiting or diarrhea is present
Your puppy is too weak to stand or walk
You notice blood in stool or vomit
There’s rapid breathing, trembling, or collapse
Puppies can dehydrate and decline fast, so early intervention is vital.
Related: My dog is drooling and lethargic (Here’s why)
Key Takeaway
A lethargic puppy that’s not eating and sleeping a lot may just be growing—but it can also signal something serious.
Because puppies are delicate and can go from mildly ill to critical quickly, you should never ignore these symptoms.
Keep a close eye, trust your gut, and don’t hesitate to reach out to your vet.
Your attentiveness could make all the difference for your puppy’s health and well-being.