Your new puppy is busy! And all that playing, learning, and growing on the outside is only part of what’s going on. All your puppy’s internal systems are busy developing too. And because puppies’ immune and digestive systems are still immature, a parasite or pathogen or even a new food can cause a lot more trouble than it would in an adult dog. The first sign of that trouble is often diarrhea.

Diarrhea is defined as wetter-than-normal poop. (While puppies are still being milk-fed, it’s normal for their poop to be soft. But once they’re weaned, their digestive systems should adapt and start producing solid stool.) Diarrhea can mean a range of consistencies from mushy to loose to watery.

Diarrhea is common in young puppies, says AnimalBiome’s Chief Veterinary Officer, Dawn Kingsbury, DVM, PhD, DACVIM. And it isn’t always a sign of health problems. An episode of diarrhea from time to time is actually pretty normal for most mammals: it’s a way for the body to quickly get rid of something it can’t or shouldn’t digest.

But sometimes diarrhea indicates a serious health issue. And in puppies, diarrhea by itself can lead to dehydration and eventually to organ damage if left untreated.

Call your veterinarian immediately if there’s any chance your puppy might have swallowed a toxic substance or foreign body or if your puppy has any of these symptoms:

• bloody diarrhea
• black, tarry stools
• fever
• vomiting
• pale gums
• lethargy or lack of energy
• refusal to eat or drink
• abdominal pain (tense belly, inability to get comfortable)
• signs of distress

The most important criterion is “how the puppy is feeling,” says Dr. Kingsbury. If your puppy has loose stools or liquid “squirts” but otherwise seems happy and is behaving normally, you can wait a day or so to see whether the diarrhea will resolve on its own. But don’t wait longer than 48 hours. By that point, even if diarrhea is your puppy’s only symptom, you should seek veterinary care.

Like adult dog diarrhea, puppy diarrhea can be caused by many different things. But puppies are especially susceptible to diarrhea because their digestive system and gut microbiome are still developing.

Here are some common causes of diarrhea in puppies:

• stress
• diet change
• antibiotic use
• gut microbiome imbalance
• intestinal parasites (e.g., roundworms, hookworms, whipworms, Coccidia, Giardia)
• bacterial infection (e.g., C. diff, Campylobacter)
• viral infection (e.g., parvo, canine coronavirus [CCoV], norovirus, rotavirus, distemper)
• ingestion of toxins, poisons, foreign objects, compost, or garbage (aka “dietary indiscretion”)
• food sensitivity (food intolerance) or food allergies
• inflammatory bowel disease (IBD) or colitis
• liver or kidney disease

Learn more about Parvo or Distemper

The puppy’s immature digestive system is a big factor in many cases of diarrhea. In a puppy transitioning from nursing to eating solid food, for example, diarrhea might be a normal reaction to new substances that the gastrointestinal tract is still learning to process. Even puppies who are accustomed to solid food may have diarrhea in response to a change in their diet.

Another big factor is the gut microbiome—the community of thousands of different kinds of bacteria and other microbes that live in your puppy’s gastrointestinal tract. This unique microbial community influences almost every aspect of your puppy’s health, including nutrient absorption, weight gain, immune functions, longevity, and mental health. As a dog grows, the gut microbiome even helps determine whether the nutrients in their food contribute to fat accumulation or lean muscle mass.

Gut microbiome imbalances are especially likely in puppies who didn’t have a nursing mother. A mother dog’s milk provides her puppies with the thousands of different kinds of dog-specific bacteria that will make up their gut microbiomes. A puppy who doesn’t get all of those beneficial microbes may not develop a well-balanced gut microbiome and may be at greater risk of digestive problems.

And because 70%–80% of the body’s immune cells live in the gut, an imbalanced gut microbiome can also mean an immune system that isn’t able to fight off pathogens and parasites effectively.

Antibiotics often cause diarrhea as a side effect. That’s because they kill off a lot of beneficial gut bacteria along with the bad bacteria they’re meant to target. The resulting imbalance among the populations of gut microbes can lead to chronic inflammation and other issues. If your puppy is prescribed antibiotics and develops diarrhea, some extra support can help them feel better during and after the treatment.

Even when it doesn’t signal an infection or other disease, diarrhea can be a threat to your puppy’s health. Because their little bodies have a higher ratio of surface area to weight than adult dogs, puppies can quickly become dehydrated. And dehydration can lead to electrolyte imbalances.

Electrolytes (like sodium and potassium) are vital for multiple functions of the body, including heartbeat (both the muscle contraction and electrical aspects), so trouble with your puppy’s electrolytes can quickly become a life-threatening emergency. In addition, ongoing diarrhea that leads to dehydration can eventually cause damage to the liver, kidneys, and heart.

Contact your veterinarian immediately if your puppy’s diarrhea is accompanied by vomiting, fever, lethargy, distress, or any other additional symptoms.

If your puppy has both diarrhea and vomiting, see your veterinarian immediately. For one thing, diarrhea and vomiting together can lead quickly to life-threatening dehydration. In addition, the combination of these two symptoms may indicate parvo or another serious infection. Or it may be a sign that that your puppy has ingested something toxic or that a foreign object or other indigestible material is causing a blockage in the digestive tract.
 
In addition to the many cleaning products and other common household chemicals that are toxic to pets, many human foods are bad for dogs, such as cherries, avocado, mushrooms, and onions. And a few are downright poisonous, even in small quantities, like raisins, grapes, and Xylitol.

Your veterinarian can run a number of tests that may help determine the cause of your puppy’s diarrhea. Checking for parasites (like Giardia) and pathogens (like C. diff) is often the first step. An ELISA antigen test and white blood cell count can be used to check for parvo. If your puppy has a bacterial infection, your veterinarian will likely recommend antibiotics. If the tests don’t find any parasites or pathogens, your veterinarian might recommend transitioning your puppy to a different diet.

If your veterinarian has determined that your puppy does not need to be treated for a viral or bacterial infection, you can focus on helping your puppy feel better. After an episode of diarrhea, it can take up to a week for your puppy’s gut lining to regenerate and their stool to return to a normal consistency. Fortunately, there’s a lot you can do to support your puppy’s developing digestive and immune systems.

Here are some tips:

• Never fast a puppy!
• Feed a bland diet that’s low in fat and easily digested (such as cooked white rice and chicken).
• Always provide plenty of fresh water. A puppy should drink about 1.5 cups of water per 10 pounds of body weight per day. If your puppy won’t drink enough water, offer a little dilute (unsalted) chicken broth.
• Mix a little fiber into their food to help firm up your puppy’s stool: try a teaspoon of Fiber One cereal, or add a little unflavored psyllium powder (start with ¼ tsp per meal and, over a few days, work up to 1 tsp per meal).
• Add a probiotic and prebiotic supplement, like S. boulardii + FOS Powder for dogs.
• Test your puppy’s gut microbiome. Microbiome testing can tell you whether your puppy’s gut contains all the different kinds of bacteria we would expect to find in a healthy dog. Our noninvasive, at-home Gut Health Test detects any missing bacterial groups, identifies harmful groups that might be causing symptoms, and gives you personalized tips for adjusting your puppy’s diet to promote the right gut flora.
• Keep up with the vaccination schedule recommended by your veterinarian. When to begin vaccinating will depend on whether your puppy had a nursing mother for the first few days of their life. (Some of the mother’s antibodies are passed along to the puppies in that first milk, called colostrum.)

Any puppy can have an episode of diarrhea from time to time. But you can help lower the chances. Here are some tips for preventing diarrhea in puppies:

• Always supervise puppies to make sure they don’t eat anything they shouldn’t.
• Puppies should be crated whenever they’re unsupervised.
• Always introduce new foods gradually over the course of 7–10 days.
• Use proper, pet-safe disinfectants to clean surfaces.
• Keep up with the vaccination schedule prescribed by your veterinarian.
• Until puppies are fully vaccinated, they should be kept away from unvaccinated dogs and public spaces.
• Talk to your veterinarian about parasite prevention and deworming.
• Clean up after your puppy and any other pets to make sure there’s no poop lying around.

Your puppy’s well-being depends on a lot of factors, and not all of them are under your control. But there’s a lot you can do to help your puppy grow up healthy and happy.

• Your puppy’s digestive system and gut microbiome are still developing, which means that even small dietary changes may cause diarrhea.
• Parasites (like roundworms and Coccidia) and pathogens (harmful bacteria like Salmonella) are also common causes of diarrhea in puppies, whose immune systems aren’t mature enough to fight off these attackers.
• Until they have been fully vaccinated, puppies are especially vulnerable to parvo and distemper, two highly contagious, often life-threatening viruses.
• Call your veterinarian immediately if your puppy’s diarrhea is accompanied by vomiting, fever, lethargy, distress, or any other additional symptoms.
• If diarrhea is the only symptom, and your puppy is otherwise behaving normally, you can wait up to 48 hours to see if the diarrhea will resolve on its own, using the tips suggested above to help them feel better. If it doesn’t, call your veterinarian.
• Untreated diarrhea can quickly lead to dehydration and electrolyte imbalance, which is very dangerous for puppies.
• A noninvasive, at-home Gut Health Test can tell you whether your puppy’s diarrhea might be due to a gut microbiome imbalance.
• If your veterinarian finds no parasites or infection, you can help your puppy’s gut heal by feeding a bland diet, mixing in a little fiber (like psyllium), and/or adding a probiotic and prebiotic supplement (like S. boulardii + FOS Powder for dogs or Gut Maintenance Plus).

More Information about Parvo in Puppies

Until they have been fully vaccinated, puppies are extremely vulnerable to the canine parvovirus (CPV, which causes parvo). Parvo is a highly contagious, potentially life-threatening infection that is associated with inflammation in the bone marrow and damage to the small intestine.
 
Symptoms of parvo: severe bloody diarrhea, vomiting, lack of appetite, severe dehydration, weight loss, lethargy, fever.

Parvo infections can spread both through direct contact with an infected dog and through indirect contact—such as exposure to an infected animal’s feces, communal water bowls, surfaces, or bedding. And the canine parvovirus can persist in the environment for months—long after the infected dog has moved on or the infected poop pile has disintegrated.
 
Vaccination is the best way to protect your puppy from parvo. Until puppies are old enough for the vaccination series, they should be kept away from other dogs and places where other dogs have been (like dog parks). At home, have visitors remove their shoes and wash their hands before interacting with your puppy.

There is no cure for parvo, recovery can take a long time, and the disease often proves fatal if left untreated. The only treatment is supportive care, which may include:

• intravenous fluids to combat dehydration
• electrolytes
• nutritional support
• anti-nausea medication
• pain relievers
• blood transfusions (in severe cases)
• fecal microbiota transplant (FMT)

Fecal microbiota transplant, or FMT, is a promising new addition to this list. A 2018 study showed that FMT helped puppies with parvo recover faster. Amazingly, FMT resolved these puppies’ diarrhea within 48 hours. Parvo infections damage cells in the small intestine, interfering with nutrient absorption and making the gut lining “leaky.”

Using FMT to provide a complete, healthy community of dog-specific gut microbes can help by healing the gut microbiome and restoring normal digestive functions. Gut Restore Supplement for dogs offers the benefits of FMT in a safe oral capsule, without the need for sedation or expensive procedures.

More Information about Canine Distemper

Another highly contagious, potentially fatal virus is the canine distemper virus (CDV), which causes distemper in dogs, attacking multiple systems in the body, including the nervous system. Distemper can spread through direct contact or through exposure to airborne droplets. In some regions, it is also found in several wild species—raccoons, foxes, wolves, coyotes, skunks, ferrets, and mink.

Symptoms of distemper: fever, runny eyes and nose, loss of appetite, diarrhea (which may contain blood or mucus), trouble breathing, cough, central nervous system effects (seizures, weakness, poor coordination.)
 
As with parvo, vaccination is the best protection against distemper. No cure for this disease exists, and the only treatment is supportive care. Antibiotics may be necessary in cases of secondary infection. Fortunately, due to high vaccination rates, distemper is not currently a problem for domestic dogs in most parts of the United States.