The skill this article is for is not diagnosis — it is recognizing, quickly, which of the things a litter throws at you can wait until morning and which cannot.
The most important first
- Puppies have very little physiological reserve: the window in which “wait and see” is reasonable is far shorter than for an adult dog.
- Diarrhea is the most common problem in a growing litter, and dehydration is what makes it dangerous in the smallest puppies.
- Coccidiosis and Giardia are common causes that routine worming does not reliably clear — both need a fecal test and a treatment plan from your vet.
- Vomiting with bloody diarrhea in an incompletely vaccinated puppy is a parvovirus emergency until proven otherwise.
- Failure to gain weight is a symptom in its own right, even with nothing else visibly wrong.
The signs that mean “call now”
Take any of these seriously, at any age: losing weight or failing to gain, refusing to nurse or eat, persistent diarrhea, blood in the urine, abnormal or persistent crying, a swollen or painful abdomen, low body temperature, labored breathing, regurgitation, cold or discolored extremities, pale or white gums, black tarry stools, or sudden weakness. A puppy showing several of these, or one of them alongside a flat weight curve, is a veterinary call rather than an overnight observation.
Pale gums, black tarry stools and weakness deserve special mention. In nursing and newly weaned puppies, hookworms passed in the dam’s milk can cause severe blood loss, sometimes before worm eggs show up in a stool test. Also watch for signs of dehydration: gums that feel dry or tacky, sunken eyes, or skin that is slow to settle back when gently lifted.
The reason for the low threshold is physiological rather than dramatic. A puppy dehydrates, cools and runs out of energy in hours, not days, and the earlier something is treated the less of it there is to treat. The weekly weights described in growth and body condition in puppies are your most useful objective input here, because they turn “seems a bit quiet” into a trend you can report.
Diarrhea, and working out what is behind it
Loose stools in a litter have a short list of usual explanations. The most common is dietary: weaning moved too fast, the gruel was thickened too quickly, or the food changed — the pacing question covered in from nursing to weaning. Next come parasites, then bacterial causes, then viral disease.
Coccidiosis deserves specific mention because it is so common in litters and so often mistaken for a food problem. The organism, Cystoisospora, is picked up from a contaminated environment or from feces, and puppies are far more likely than healthy adults to actually become ill from it. Signs range from diarrhea to bloody or mucoid stools, lethargy, weight loss and dehydration. Diagnosis is a fecal examination — and a negative early test is worth repeating, since oocysts are not always being shed when signs begin. Treatment is prescription-only and specific, which is the practical point: no amount of worming treats it. Prevention is the same routine that prevents most things here — prompt removal of feces and frequent cleaning.
Giardia behaves similarly, and the two often circulate in the same conditions. Persistent or recurring diarrhea in a litter that is being wormed on schedule is a reason to have feces tested rather than to repeat the wormer. Routine worming does not reliably clear either parasite; both need a stool test and a plan from your vet, as covered in parasites and worming schedules.
Coccidia and Giardia keep returning if the environment stays contaminated. Giardia cysts are infective as soon as they are passed, and coccidia eggs resist most disinfectants. Pick up feces straight away, clean surfaces and let them dry fully, and ask your vet whether to bathe the puppies at the end of treatment.
Parvovirus, and why it is treated differently
Vomiting, profuse and often bloody diarrhea, rapid collapse and dehydration in a puppy between six weeks and six months is the picture that must be assumed to be parvovirus until a vet says otherwise. It moves fast, it has a real mortality rate — though with prompt intensive treatment most puppies survive — and treatment is supportive and intensive — which means the deciding factor is usually how early the puppy gets to a vet.
Two things breeders get wrong here. The first is reassurance from a single vaccination: a partially vaccinated puppy is not a protected puppy. The second is treating it as one puppy’s problem, when it is in fact a kennel event — isolation, and the disinfection regime in infection control and biosecurity for the litter, start the same hour as the phone call.
Not every case shows blood: around one in four affected dogs has diarrhea without visible blood. Signs usually appear five to seven days after exposure but can take up to two weeks, so littermates that look well today may still become ill. If parvovirus is confirmed, tell the owners of any puppy that has already left, and their vets.
In practice
A breeder notices one six-week-old puppy with loose stools and attributes it to the new food, which was introduced the same week. By the next morning the puppy is quiet and two littermates are also loose. What changes the outcome is not a better guess about the cause but the speed of the call — and the decision to separate the affected puppies and their bowls immediately, before knowing what it is.
(Illustrative, composite scenario.)
The rest of the usual list
Respiratory infections show as coughing, sneezing and nasal discharge, spread easily in a group, and matter more in puppies than in adults. Eye problems — discharge, swelling or a closed eye after the eyes have opened — need looking at rather than bathing and hoping. Skin infections, often as small pustules on the belly, are common and usually straightforward but should be seen if they spread.
Two conditions are worth recognizing by name because they alarm breeders who have not met them. Umbilical hernias are relatively common, usually small, and the decision about whether anything needs doing is a veterinary one, often deferred. Juvenile cellulitis — “puppy strangles” — presents as sudden facial swelling, pustules and enlarged lymph nodes in a young puppy, is believed to be immune-mediated, and needs prompt veterinary treatment, usually with medication that calms the immune response.
Problems carried over from the neonatal period — fading puppies, hypoglycemia, hypothermia — belong to the neonatal period, which covers them in the detail they need. And several congenital findings surface for the first time at the pre-sale veterinary check, which is one reason that check exists.
Some puppy parasites can also infect people. Roundworm eggs can survive in soil for years, and children are most at risk. Wash hands after handling puppies or cleaning up, and keep young children away from the puppy toilet area.
What to do while you wait
Isolate the affected puppy or puppies with their own bowls and bedding. Keep them warm, and offer water. Weigh them, take a temperature if you can, and write down what you see — when it started, how many are affected, what the stools look like, what and when they last ate. Do not medicate: there is no safe household remedy for a sick puppy, for the reasons set out in veterinary care and medication for puppies. Then call, with your notes in front of you.
When to call your vet
- Vomiting together with diarrhea, or any blood in the stool, in a puppy that is not fully vaccinated — call before you travel so the clinic can isolate you
- Pale gums, black tarry stool, or sudden weakness
- Diarrhea lasting more than a day, or in more than one puppy
- A puppy refuses food, is dehydrated (tacky gums, sunken eyes) or feels cold
- Sudden swelling of the face, muzzle or eyelids, or swollen glands under the jaw
- Labored or rapid breathing, or a cough with nasal discharge
- If in doubt, call — your vet would rather hear from you early.
Work on it
A few minutes here will teach you more than re-reading the article.
Ask yourself
- Do I know which signs mean “call now” without having to look them up?
- Would I test for coccidia and Giardia, or assume diarrhea is dietary?
- Do I have an isolation plan — space, bowls, bedding — that I could use today?
Find out & check
- Find out your vet’s out-of-hours arrangements and write the number where anyone in the house can find it.
Do one thing
- Put a thermometer, a scale and a notebook in the puppy room, so that a call to the vet starts with numbers.
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Sources & further reading
- Merck Veterinary Manual — Canine Parvovirus Infection (Parvoviral Enteritis in Dogs). merckvetmanual.com
- Cornell University College of Veterinary Medicine, Riney Canine Health Center — Coccidia in dogs. vet.cornell.edu
- Merck Veterinary Manual — Management of the Neonate in Dogs and Cats. merckvetmanual.com
- VCA Animal Hospitals — Parvovirus in Dogs. vcahospitals.com
- Companion Animal Parasite Council (CAPC) — Giardia guidelines. capcvet.org
- Companion Animal Parasite Council (CAPC) — Hookworm guidelines. capcvet.org
- VCA Animal Hospitals — Roundworm Infection in Dogs. vcahospitals.com
- MSPCA-Angell — Understanding Puppy Strangles. mspca.org
Where evidence is limited, recommendations rest on established practice and expert judgment, and may be updated as knowledge develops. This article is written to help you recognize problems and act — it is not a substitute for veterinary diagnosis or treatment.
Next steps
- Read next: Veterinary care and medication for puppies.
- Related: Infection control and biosecurity for the litter.
- Return to the area hub: Raising a healthy litter.