Intestinal worms -- roundworms, hookworms, whipworms, tapeworms -- are among the most common health issues in dogs and cats across all life stages. Puppies and kittens are particularly vulnerable because they can be infected before birth or through their mother's milk, and because their immune systems are still developing. But adult pets are not immune, and indoor animals can still be exposed through contaminated soil, prey animals, or fleas.
This guide covers the main types of intestinal parasites relevant to dogs and cats, typical deworming frequency recommendations by life stage, and why routine parasite control matters even for pets that seem healthy and stay mostly indoors.
Roundworms (Toxocara canis in dogs, Toxocara cati in cats) are among the most prevalent intestinal parasites worldwide, particularly in young animals. Puppies and kittens can be infected in utero or through nursing, making early deworming essential regardless of the mother's apparent health. Adult roundworm infections are also possible through environmental exposure.
Hookworms can cause blood loss -- significant enough in young or small animals to cause anemia, and in severe cases, life-threatening. Whipworms (primarily in dogs) live in the large intestine and can cause chronic intermittent diarrhea. Tapeworms are typically transmitted through flea ingestion or, for some species, through consuming prey animals, and are more often visible in stool or around the anal area as small rice-grain segments.
Giardia and Coccidia are protozoan parasites rather than worms, but they cause intestinal problems in young animals and are often addressed as part of a broader parasite control conversation. A fecal exam from your vet is the most reliable way to identify which specific parasites are present.
Given how commonly puppies and kittens are infected at or before birth, standard recommendations call for deworming to begin early and be repeated frequently. For puppies, a widely recommended schedule starts deworming at 2 weeks of age, then at 4, 6, and 8 weeks, and again at 10 and 12 weeks. Deworming is typically continued monthly until the puppy is 6 months old, at which point they transition to an adult schedule.
For kittens, deworming starting at 3 weeks of age, repeated every 2 weeks until 8 weeks, then monthly until 6 months is a common guideline. Nursing mothers are also typically treated, as they can pass worms to offspring through milk.
The specific products and exact timing your vet recommends may differ based on the parasites most common in your region, the dewormer's spectrum of activity, and whether the puppy or kitten is showing any symptoms. Fecal testing alongside deworming gives the most complete picture.
For adult dogs and cats, the appropriate frequency of deworming depends on lifestyle risk. Pets with outdoor access, hunting behavior (catching and eating prey), exposure to other animals, or a history of flea infestation are at higher risk than strictly indoor animals with controlled environments.
Many veterinary parasitology guidelines recommend year-round monthly heartworm preventives for dogs that also cover some intestinal parasites (such as roundworms and hookworms), combined with regular fecal testing -- typically 1-2 times per year for lower-risk dogs and up to 4 times per year for higher-risk ones. Tapeworm treatment is typically given as needed rather than on a fixed schedule, often triggered by a confirmed flea infestation or observed tapeworm segments.
For cats, similar principles apply: lower-risk indoor cats may need less frequent treatment, while cats with outdoor access or hunting behavior benefit from more regular parasite control, including deworming alongside flea prevention.
A common assumption is that indoor pets are safe from intestinal parasites. In reality, the risk is lower but not zero. Parasite eggs can survive for long periods in soil and can be tracked in on shoes or clothing. Fleas -- which can be brought in the same way -- transmit tapeworms when ingested during grooming. Rodents that occasionally enter the home can carry parasites that a hunting cat or opportunistic dog might encounter.
Additionally, some intestinal parasites (particularly roundworms and hookworms) are zoonotic -- they can infect humans, particularly children who come into contact with contaminated soil or pet feces. This public health dimension is one reason veterinary and public health guidelines emphasize routine parasite control even in lower-risk households.
A fecal flotation test, performed by a veterinary laboratory on a small stool sample, can identify the eggs or oocysts of most common intestinal parasites. This allows targeted treatment rather than blanket guessing -- different parasites require different dewormers, and knowing what's actually present makes treatment more effective.
Many vets include a fecal exam as part of annual or semi-annual wellness visits for this reason. If your dog or cat has diarrhea, weight loss despite good appetite, visible worm segments in stool, or a pot-bellied appearance (more common in heavily infected young animals), a fecal test is an important early step before assuming a cause.
If you have a new puppy or kitten, deworming should begin as early as 2-3 weeks of age regardless of whether you see symptoms -- assume exposure until proven otherwise, particularly in pets from shelters, breeders, or outdoor environments. For adult dogs and cats, discuss your pet's specific risk factors with your vet at their next wellness visit, and ask whether their current parasite prevention covers intestinal parasites alongside heartworm and fleas.
Signs that may indicate an active intestinal parasite problem include diarrhea (especially with blood or mucus), weight loss or poor growth in young animals, vomiting, lethargy, or visible worms or segments in stool. These warrant a prompt vet visit and fecal testing rather than at-home deworming without diagnosis.
Standard recommendations begin puppy deworming at 2 weeks of age, then every 2 weeks until 8 weeks, and monthly thereafter until 6 months old. This early start is important because puppies can be infected before birth and through their mother's milk. Your vet will confirm the best products and schedule for your puppy.
Over-the-counter dewormers are available, but they typically cover only a limited range of parasites -- often only roundworms and hookworms, and not all species. Without a fecal test to know what parasites are present, it's easy to miss others. Prescription dewormers often have broader or more targeted activity. A vet visit and fecal test is the most reliable approach, especially for puppies, kittens, or pets showing symptoms.
Many monthly heartworm preventive products for dogs include ingredients that also control roundworms and hookworms. Some products also address whipworms. However, none of the standard heartworm preventives reliably cover tapeworms, which require separate treatment. Check the label of your specific product, or ask your vet what parasite coverage it provides.
Several intestinal parasites of pets are zoonotic -- they can infect humans. Roundworms and hookworms are the most notable, with children being at higher risk through contact with contaminated soil or accidental ingestion of eggs. Good hygiene (washing hands after handling pets or cleaning litter boxes, picking up pet waste promptly, keeping sandboxes covered) reduces risk alongside keeping pets on a regular parasite control program.
Indoor cats have genuinely lower risk, but not zero risk. Parasites can enter the home on shoes and clothing; fleas (which transmit tapeworms) can be brought in from outside; and rodents entering the home represent another exposure route. A conversation with your vet about your cat's actual risk level and what routine monitoring makes sense is more useful than a blanket assumption that an indoor cat is completely safe.