How do i know if my dog has worms?

If you’re reading this because you suspect your dog might have worms, you’re in the right place. The guidance below is written from the perspective of a clinician who sees these cases regularly: practical, direct, and focused on what you can observe and do today.

Why understanding worms protects both your dog and your family

Worm infections are more than an unpleasant surprise in stool; they may affect a dog’s nutrition, energy and long‑term wellbeing. Left unchecked, some worms can cause chronic weight loss, anemia, intestinal damage or even life‑threatening organ problems. I typically see pups with poor weight gain or dull coats where intestinal parasites are a big contributor.

Many parasites can also affect people in the household. While the risk varies by parasite and behavior, children or immunocompromised people who play in contaminated soil or handle infected feces may be at higher risk. That zoonotic potential is a practical reason to act quickly rather than wait and see.

Knowing when to watch at home and when to call the veterinarian matters. Minor, early signs may be monitored and tested, while severe signs require immediate attention. A prompt, targeted response usually shortens illness and reduces the chance of spread to other pets and people.

The short answer — how to tell at a glance if your dog might have worms

Typical signs that may suggest worms include intermittent or persistent diarrhea, a potbellied appearance in puppies, visible worms or segments in stool (or around the anus), scooting, weight loss despite a normal appetite, and a dull coat. Some worms also stimulate coughing or breathing changes when larvae migrate through the lungs.

Veterinarians usually confirm infection with fecal tests; a fecal flotation looks for eggs, and some clinics use antigen or PCR tests for parasites not reliably seen on flotation. Heartworm infection is commonly screened with a blood antigen test because it doesn’t show up on fecal exams.

Most common intestinal worms respond well to licensed dewormers and supportive care. Recovery for routine intestinal parasites is often days to a few weeks, with follow‑up testing recommended. Heartworm and some tissue parasites typically require a longer, staged treatment plan and monitoring.

How dogs pick up parasites: common routes of infection

Different worms reach dogs in different ways and cause distinct problems. Roundworms are often acquired by ingesting eggs from contaminated soil or through the placenta or milk; hookworms can be swallowed or penetrate the skin; whipworms are usually picked up by ingesting contaminated material; tapeworms commonly result from swallowing infected fleas or prey; heartworm is transmitted by mosquitoes that carry the infective larvae.

The parasite life cycle generally includes egg, larval and adult stages, and dogs may be involved as definitive hosts (where the parasite reaches maturity) or accidental hosts. For example, roundworms mature in the dog’s intestines and shed eggs in feces, while heartworm larvae migrate via the bloodstream to the heart and pulmonary arteries where adults develop over months.

Worms harm dogs in several ways: they may rob nutrients and calories, impair growth in puppies, or cause blood loss leading to anemia (common with heavy hookworm burdens). Intestinal inflammation and damage can cause chronic diarrhea and poor absorption. Migrating larvae may irritate lungs, liver or other organs, producing coughing or systemic illness.

Everyday situations that raise a dog’s risk of infection

Puppies are at particular risk because they can acquire roundworms and sometimes hookworms from their mother before or shortly after birth; their immune systems are immature and burdens that a healthy adult dog would tolerate can be dangerous. Older dogs with weakened immunity or concurrent illness may also be more susceptible.

Behavior matters: dogs that scavenge, hunt rodents, eat feces or groom fleas are more likely to be exposed. Raw diets and feeding uncooked game increase risk for certain parasites. Dogs in shelters, kennels or multi‑dog households face higher exposure simply because more animals mean more opportunity for parasites to spread.

Regional and environmental factors change risk profiles. Areas with many mosquitoes have higher heartworm risk; sandy or warm soils may favor hookworm larvae. Missing or delaying routine preventives—monthly heartworm and broad‑spectrum parasite controls—creates a gap where infections can establish.

Warning signs and red flags that need prompt attention

Seek veterinary attention right away if your dog has severe, persistent diarrhea or vomiting, especially if it’s producing large volumes, blood, or is accompanied by weakness. Rapid weight loss, fainting or pale gums may suggest significant blood loss and anemia, which can be life‑threatening.

Visible worms or segments in feces or around the anus (tapeworm segments look like short, rice‑grain pieces) should prompt testing and treatment; seeing actual worms is more than cosmetic evidence and usually indicates a treatable infection. Respiratory distress, collapse, sudden severe abdominal pain, or ongoing lethargy require urgent care—these can be signs of heavy parasite burdens, organ involvement, or complications.

How to respond: a practical action plan for concerned owners

1. Observe and record symptoms and recent exposures: note appetite, stool changes, coughing, any scavenging, flea sightings, travel history, or missed preventives. A clear timeline helps the vet choose tests and treatment.
2. Collect a fresh fecal sample if you can: scoop the most recent stool into a clean, sealed container and refrigerate it immediately. Many clinics prefer a sample no more than 24 hours old for accurate testing.
3. Contact your veterinarian for testing: explain the signs, exposures and provide the fecal sample. Expect a fecal flotation and possibly a blood antigen test for heartworm depending on symptoms and regional risk.
4. Follow the prescribed treatment plan: give the full course of dewormer exactly as directed, including any repeat doses. Some protocols require repeated treatments weeks apart because drugs target adults but not newly hatched larvae.
5. Complete follow‑up testing: a repeat fecal exam is usually scheduled 2–4 weeks after treatment to confirm the burden has dropped, and additional checks may be recommended depending on the parasite. For heartworm, staged monitoring and sometimes prolonged therapy are needed.
6. Alert household members if you suspect a zoonotic parasite, and advise them to speak with their physician if they develop symptoms. Practice thorough handwashing during handling and cleanup.

Keeping worms away: effective steps to prevent reinfection at home

Prompt and frequent feces removal is one of the simplest, most effective steps you can take. Removing stool daily reduces environmental egg and larval load and lowers the chance your dog or others will re‑ingest infective stages.

Maintain a regular schedule of preventive medications per your veterinarian’s guidance: monthly heartworm preventives that also treat many intestinal parasites are widely available and reduce the need for reactive treatments. I notice that owners who fall behind on monthly preventives commonly see recurrences.

Discourage scavenging and control access to raw‑food exposures. Prevent dogs from hunting or eating wild prey and manage flea control to cut tapeworm risk. Routine veterinary fecal checks—often annually for adults and more frequently for puppies—help catch low‑level infections before they become a problem.

Vet-recommended tools and supplies for detection, treatment and prevention

• Clean, sealable sample containers or a fecal collection kit to preserve a fresh stool sample for the clinic.
• Disposable gloves and sturdy poop bags for hygienic cleanup, plus an effective surface disinfectant safe for pets to reduce environmental contamination.
• Vet‑prescribed dewormers specific to the parasite identified, and a reliable monthly heartworm/flea/tick preventive recommended by your veterinarian.
• Simple mosquito control measures in high‑risk areas—screens, remaining indoors during peak mosquito times, and environmental steps that reduce standing water—help lower heartworm risk.

Evidence, sources and further reading

• American Veterinary Medical Association: “Intestinal Parasites in Dogs and Cats” — https://www.avma.org/resources-tools/pet-owners/petcare/intestinal-parasites-dogs-and-cats
• Centers for Disease Control and Prevention (CDC): “Parasites – Roundworm (Toxocariasis)” and “Parasites – Hookworm” pages — https://www.cdc.gov/parasites/toxocariasis/ and https://www.cdc.gov/parasites/zoonotic_hookworm/
• Merck Veterinary Manual: “Intestinal Parasites of Dogs” — https://www.merckvetmanual.com/dog-owners/gastrointestinal-disorders-of-dogs/intestinal-parasites-of-dogs
• Merck Veterinary Manual: “Heartworm Disease (Dirofilariasis) in Dogs” — https://www.merckvetmanual.com/circulatory-system/heartworms-in-dogs/overview-of-heartworm-disease
• American Heartworm Society: “Current Canine Guidelines for the Prevention, Diagnosis, and Management of Heartworm Disease in Dogs” — https://www.heartwormsociety.org/