Last updated: 26 September 2026
Giardia infection in dogs is treated with medication prescribed by a vet, typically fenbendazole or metronidazole for 3–5 days, sometimes both together. The course of treatment alone is often not enough: the cysts survive for months in the environment and on the coat, so the dog can easily become reinfected. It is recommended to bathe the dog on the last day of treatment and to clean the bed, bowls and floor thoroughly, then let them dry. Home remedies do not kill Giardia. An antigen test carried out immediately after the course can be misleading, because the antigen may remain detectable even after successful treatment.
In this article we explain how treatment works, why Giardia comes back so often, how to clean, and when it makes sense to test again. You can read about what Giardia is and what symptoms it causes here: Giardia in dogs.
How is Giardia treated in dogs?
According to the CAPC (Companion Animal Parasite Council) recommendation, every symptomatic, Giardia-positive dog should be treated. The vet typically chooses from the following:
| Active ingredient | Typical duration | Note |
|---|---|---|
| Fenbendazole | 3–5 days, once a day | A widely used deworming agent that is also effective against Giardia. |
| Metronidazole | 5 days, twice a day | An antibiotic. Prescription only, with dosing by a vet. |
| Fenbendazole + metronidazole | 5 days | Used in stubborn or recurring cases. |
| Febantel + pyrantel + praziquantel combination | 3 days | Some combination dewormers are also effective against Giardia. |
The dose and length of the course are always set by the vet based on the dog's body weight and condition. Do not give leftover medication, human products or medicine prescribed for another dog on your own initiative.
For dogs that are positive but symptom-free, the majority opinion of the CAPC board is that treatment is not necessarily required. Exceptions may apply if the dog lives with small children, elderly or immunocompromised people, or many other dogs. This is the vet's decision.
Is there a home treatment for Giardia?
Many people look for a home remedy, but there is no home remedy that has been proven to kill Giardia. Diet, probiotics or easily digestible food can ease the symptoms, but they do not eliminate the parasite. As a result, the dog can continue to shed cysts and infect other animals. Some “natural” remedies are downright dangerous. Garlic and onion, for example, are toxic to dogs. What really is up to you at home is cleaning and bathing: without these, the medication will not work well either.
Why does Giardia come back so often?
According to Cornell University, Giardia cysts are resistant and can survive in the environment for months. There are three common reasons for relapse:
- Reinfection from the environment: from cysts left on the bed, the floor, in the garden, on the bowls and on the dog's own coat.
- Untreated companion animals: if another dog or cat is also infected, they pass the parasite back to each other.
- Incomplete course: missed doses, treatment that is too short, and rarely strains that are less sensitive to the medication.
In an Italian study published in 2021, 24 infected dogs living at home were treated with fenbendazole or metronidazole and followed up for 50 days. Seven days after treatment, 33% of the dogs treated with fenbendazole and 42% of those treated with metronidazole were still shedding cysts. These dogs were treated again. By day 21 all dogs were negative, but on day 50 two dogs in each group were positive again. The authors considered reinfection from the environment and intermittent cyst shedding to be the most likely cause. Their conclusion: medication alone is not enough to bring Giardia under control.
Cleaning and bathing plan during treatment
| When? | What to do |
|---|---|
| Daily, during treatment | Pick up faeces immediately. Wash the water and food bowls with hot water. After walks, wipe the dog's paws and the area under the tail. |
| 1–2 times during treatment | Wash the bed, blankets and soft toys at the highest possible temperature. Clean the floor with a steam cleaner or disinfectant. |
| On the last day of treatment | Bathe the dog with shampoo, paying particular attention to the area under the tail and the hind legs. Then switch to a clean bed. |
| Always after cleaning | Let surfaces dry thoroughly. Cysts like moisture and cannot withstand drying out. |
| Garden, yard | Pick up faeces immediately. According to Cornell, cysts on a lawn are only killed by direct sunlight and drying out, so avoid damp, shady areas and puddles. |
According to the CAPC, surfaces can be cleaned with steam cleaning or commercially available disinfectants, and thorough drying is needed after cleaning. It recommends bathing the dog on the last day of treatment so that cysts stuck to the coat do not cause reinfection.
Is a follow-up test needed after treatment?
This is the most common misunderstanding about Giardia. The CAPC and Cornell both warn: antigen tests (ELISA, rapid test) and PCR can remain positive for some time even after successful treatment, so they are not suitable for deciding whether treatment has failed or reinfection has occurred.
- If the symptoms have resolved: a routine follow-up test is generally not needed.
- If diarrhoea persists at the end of the course: in line with the CAPC recommendation, the vet may carry out a microscopic faecal examination (flotation) 24–48 hours after the end of treatment.
- If diarrhoea returns weeks later: in this case a home Giardia rapid test is a good indicator of whether Giardia is behind it again. If the result is positive, contact a vet.
What about the other dogs and cats?
In multi-pet households, kennels and shelters, Giardia rarely stays with a single animal. If one dog is positive, discuss with the vet which animals need to be examined and treated. It is worth carrying out the cleaning plan for all of them at the same time. The CAPC also recommends screening symptom-free dogs arriving at shelters, boarding kennels or dog training schools.
For breeders and shelters, the pack of 5 is more economical, allowing a litter or a group to be tested at once. We have a separate article on Giardia infection in cats: Giardia in cats.
Can humans catch it from dogs?
According to the CAPC, the Giardia most commonly found in dogs is of genotypes C and D, which only infect canids. Only genotypes A and B can spread to humans, and these are less common in dogs. Human infections come mainly from other people, contaminated water and food; according to the CAPC, transmission from dogs to humans appears to be rare. Thorough handwashing, picking up faeces immediately and supervising children during treatment are still recommended.
Frequently asked questions about Giardia treatment
How long does Giardia treatment take in dogs?
The course of medication typically lasts 3–5 days. Because of the cleaning and bathing, the whole process takes about a week. In stubborn cases the vet may repeat or combine treatments.
What medication is needed for Giardia?
Most commonly fenbendazole or metronidazole, sometimes both together, or certain combination dewormers. The product and the dose are always prescribed by a vet.
Can Giardia be treated at home?
Not without medication. Diet and probiotics can ease the symptoms, but they do not kill the parasite. At home, cleaning, disinfecting and bathing are your job – without them the treatment will not last.
Why does Giardia come back after treatment?
Most often because the dog is reinfected from the environment or from its own coat, or because an untreated companion animal passes the infection back. Less often, the course was not completed.
When can I test again?
It is not worth using an antigen test immediately after treatment, because the antigen may still be detectable after successful treatment. If the symptoms persist, the vet will carry out a microscopic examination. If diarrhoea returns weeks later, a new rapid test is a good indicator of whether it is Giardia again.
Do the other dogs need to be treated too?
That is for the vet to decide. In multi-pet households the other animals are often examined as well, and it is worth carrying out the cleaning plan for all of them at the same time.
Summary
Giardia is curable, but treatment only lasts if three things come together: the full course of medication prescribed by a vet, bathing the dog at the end of treatment, and thorough cleaning and drying of the home. An antigen test immediately after the course can be misleading. However, if diarrhoea returns weeks later, a home rapid test will quickly show whether Giardia is back.
Giardia Ag rapid test for dogs and cats →
If diarrhoea comes back: from a stool sample, in 5–10 minutes. Available in a pack of 5 for multi-pet households and kennels.
Sources
- Companion Animal Parasite Council (CAPC): Giardia – guidelines. capcvet.org
- Cornell University College of Veterinary Medicine: Giardia – infection, treatment and prevention. vet.cornell.edu
- Effectiveness of Fenbendazole and Metronidazole Against Giardia Infection in Dogs Monitored for 50 Days in Home Conditions. Frontiers in Veterinary Science, 2021. PMC8032893
Important: this article provides general information and does not replace veterinary advice. Medication, dosing and follow-up testing should always be determined by a vet. MancsLab rapid tests are intended for preliminary screening at home.