How to Tell if a Dog Has Worms

Dr. Joe Alcorn, M.S., D.V.M.

Dr. Joe Alcorn is founder of Care Animal Hospital in Temecula, California. He has a Bachelor of Science in Biology and Doctor of Veterinary Medicine from Colorado State University. He is a member of the American Veterinary Medical Association and his advice has been featured in large publications like Bustle and Martha Steward.

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One of the most common health issues dogs face is worms. Having a worm infection can be extremely unpleasant for your dog. That is why it is important for you to understand the symptoms and know how to tell if a dog has worms.

How to Tell if a Dog Has Worms 

Once your dog has an infestation of worms, there are certain noticeable symptoms they start to display. By learning to identify these symptoms, you can get treatment for your dog before the infestation escalates.


There are a few general symptoms that can indicate a worm infection in dogs. These symptoms might not certainly point to a worm infestation in all cases, however, they are commonly associated with it.


Frequent vomiting might not necessarily indicate a worm infection, however, most worms can be seen in the vomited substance. If your dog is constantly vomiting or unable to keep down any swallowed substance this might indicate the presence of worms.


Another indicator of worm infection in your dog is repeated dry cough or wheezing. Some types of dog worms infect the immune system making your dog susceptible to a common cold or cough.

Reduced Energy

Dogs with a worm infection might experience a change in appetite or loss of nutrients. This can cause general body weakness and lethargy. Constant stooling or vomiting will also make your dog very weak. 

Weight Loss

Drastic or rapid weight loss in a dog is a common indicator of worms in dogs. Most dogs are unable to keep down their food or supplements while battling a worm infestation. Some types of worms also target the digestive system.


A worm infestation might trigger diarrhea in most dogs. If you notice blood or mucus in your dog’s poop, you should bring them in for worm treatment immediately. Some types of worms can also be found in their poop.

Hair Loss

Hair loss can occur as a result of excessive itching or biting. This can indicate the presence of tapeworms. Once your dog aggressively keeps scratching a spot, the hair around that spot starts to fall off or appear scanty.

Skin Allergies or Irritation

A severe worm infestation can be detected through severe skin rash or allergy. This irritation can happen as a result of the dog continuously itching the part of the body where they can feel the presence or movement of the worms.


An unusual biting or scratching of its bottom by your dog is a telltale sign of a worm infestation. Worms have a wriggling feeling that will continuously bother your dog. In an attempt to try to expel it from their body, they will try scratching, biting, or scooting.

Different Types of Worms in Dogs

There are five common types of dog worms. Each type of worm presents specific symptoms that can help you tell them apart. 

Dog suffering from worm infestation


Hookworms are really small worms that commonly reside in a dog’s small intestine. They tend to feed on blood which can cause anemia in your dog when left untreated. A fully grown hookworm would be undetectable to the naked eye. They are commonly passed around in poop or from the mother’s milk and can infect humans or other animals. 

Puppies are most affected by this type of worm. Hookworms tend to grow in a moist or warm environment.


The most common symptoms of hookworm in dogs include:

  • General weakness
  • Anemia 
  • Dermatitis
  • Pneumonia
  • Lung damage 
  • Melena 
  • Diarrhea


Roundworms are also commonly found in a dog’s intestines. They are commonly transmitted through contact with infected feces or from mother to pup. While the eggs can only be seen under the microscope, adult roundworms can be seen with the naked eye. They can be noticed in clusters coughed up by the dog or in your dog’s poop.

Toxocara Canis is the most common type of roundworm in dogs. This type of roundworm can also infect humans. 


Common symptoms of roundworm are:

  • Weight loss
  • Lethargy
  • Diarrhea 
  • Poor growth rate
  • Vomiting


Whipworms are mostly found in a dog’s colon or its blind gut. Although its eggs can commonly be found in dog poop, adult whipworms tend to stay within the dog’s colon. Whipworms can be very harmful to a dog due to their distinct living environment. They can be difficult to find and can survive as long as five years in the egg state.

They are smaller in size than roundworms however, they can be visible to the human eye. They are mostly gotten from ingesting an infected substance.


The most easily identified symptoms of whipworms include:

  • Visible mucus on dog’s feces
  • Bloody feces
  • Extreme weight loss


Tapeworms are mostly found attached to a dog’s small intestine in a hook-like manner. They feed off half-digested food in your dog’s intestine, thereby robbing your dog of its vitamins and nutrients. A dog can easily catch tapeworm by ingesting a flea-infected substance or a flea.

If you find small white substances like rice grains around your dog’s sitting or sleeping area, this could indicate the presence of tapeworms. 


A few symptoms of tapeworm in dogs generally are: 

  • Irritability
  • Irregular growth
  • Excess eating 
  • Malaise 
  • Unusual itching 
  • Tapeworm presence in dog poop
Dog being checked by a veterinarian


Heartworms are commonly the most preventable type of dog worm. Although, they can be deadly. They are only transmitted to the dogs by infected mosquitoes. Heartworms mostly live in a dog’s pulmonary arteries or heart. When left untreated they can lead to serious organ failure or death.

The typical incubation period is just around six months before they settle in the dog’s circulatory system. They are mostly detected through a blood test as the symptoms don’t present in the early stages.


Some of the common symptoms of heartworm are:

  • Wheezing 
  • Difficulty breathing 
  • Lethargy
  • Coughing

How to Treat Worms in Dogs

When left untreated or diagnosed late, worms can lead to other serious health conditions in dogs or death in severe cases. If you notice any of these symptoms in your dog or find traces of worms in their fecal matter, you should reach out to me for professional advice if you have any questions regarding your dog. 

I can run specialized tests to determine what type of worm infestation your dog is dealing with and the best treatment course. You should not attempt to treat your dog yourself to avoid further health complications.

Worm infestations in dogs should not be left untreated for long because not only are they harmful to the dogs, but some of them can also be passed to humans too.

How to Prevent Worms in Dogs

There are a few preventive measures to take as a dog owner, to reduce the risk of a worm infestation. These measures are:

  • Regular vet checkups. Go along with a fecal sample from your dog for further and accurate testing.
  • Worm or parasite prevention treatments should be administered to nursing dogs and their litter. This can eliminate worms that tend to incubate for a long period.
  • Disinfect your dog’s personal effects such as beds, and toys.
  • Regular fecal examination and deworming for dogs that spend a lot of time outdoors
  • Keep your dogs and their surroundings clean at all times
  • Dispose of your dog’s waste in public spaces. Use sealable or thick bags to prevent other dogs from eating them up. 
  • Limit your dog’s exposure to objects, food, or soil when you are outside your home


Worms in dogs can be preventable with proper care. When left untreated or undiagnosed they can cause severe health issues or death. Firstly, reach out to me to consult on the best line of treatment before medicating your dog for worms.