Health
Soft stools that come and go, pale, sharp-smelling, in a puppy who is otherwise bright. Giardia is common in young dogs and settles into a home if you let it.
Caution. A puppy or elderly dog with watery diarrhoea, bloody or black stool, repeated vomiting, or a dog who will not eat or drink or looks dehydrated: see a vet the same day. In a puppy, severe diarrhoea can be parvovirus.
Do not look for the answer in a Facebook group, on TikTok or on a forum. Look for someone trained for this: your dog's own veterinarian, the only person who can examine, investigate and treat them.
Use this page to know what to observe, what to note and what to ask at the appointment, not to treat at home. If you still have doubts after a consultation, ask another vet or a specialist (dermatologist, internist) for a second opinion, not a group. And if you do not have a regular vet yet, find one now, while your dog is healthy: how to choose a veterinary clinic.
The puppy is three months old and came from a breeder or a rescue kennel. His stools have been soft since the day he arrived. Three days look fine, then it starts again: pale or yellowish, some mucus, and a sharp smell you have not had from a dog before. You have wormed him and changed his food, and nothing has shifted. Or it is an adult dog who drank from a puddle on a hill walk and has been loose for a fortnight. When the vet says "giardia" it sounds exotic. It is in fact one of the most common gut parasites in young dogs, and getting rid of it depends almost as much on what you clean at home as on the treatment.
Giardia is a microscopic, single-celled parasite that clings to the lining of the small intestine. People often assume it is a worm; it is not. A dog picks it up by swallowing cysts, the tough resting stage, from water, grass, another dog's coat or his own paws. The cysts come out in the faeces ready to infect the next dog, or the same dog a second time.
Most dogs with giardia are not seriously ill. They get soft stools that come and go, and plenty show nothing at all. Some situations, though, should not wait for next week's appointment:
In a puppy, severe diarrhoea can be parvovirus. Telling the two apart takes a test at the practice, however many puppies you have raised.
The diagnosis comes from a faecal test. Your job is to bring a good sample and a clear picture of the last few days.
What the stool looks like. Classic giardia stool is soft to pasty, pale or yellowish, greasy-looking, sometimes with mucus, and it smells strong. It comes in waves: three bad days, two nearly normal ones, then round again. Take photos on the bad days and the good ones; a vet gets more from thirty seconds of scrolling than from a long description.
How often, and how. A dog with giardia tends to go a few times a day and pass a lot. If he goes often, passes little and strains, the problem is more likely in the large bowel, and that tells the vet where to look.
His weight. Once a week, same scales. Giardia interferes with fat absorption, and you do see puppies who eat well but still do not grow as they should.
Where he could have picked it up. Breeder, rescue, pet shop, boarding kennels, group classes, puddles, streams, the dog park. If you have other dogs, check their stools too.
The sample. Your vet will say how they want it. Usually a fresh stool about the size of a walnut, in a clean pot, kept cool until you get there. Cysts are not shed in every stool, so you may be asked for samples from three separate days, in one pot or three.
| What you see | Does it fit giardia? | Other common causes |
|---|---|---|
| Soft, greasy, smelly stool that comes in waves | Yes, that is the classic picture | A change of food, pancreas problems |
| Watery, bloody diarrhoea in a puppy | Rarely | Parvovirus, worms, a swallowed object |
| Mucus and fresh blood, lots of small stools | Less likely | Colitis, whipworm, stress |
| Eating a lot, losing weight, bulky stool | Possibly | Pancreas not producing enough enzymes, worms |
| Nothing, but another dog at home has giardia | Could be a carrier | Worth testing him as well |
Use the table to get your bearings. Several parasites and several illnesses produce exactly the same stool.
This one surprises a lot of owners: a dog with no diarrhoea and a positive test found by chance is not always treated. Plenty of healthy dogs carry giardia and clear it themselves. Your vet decides based on the dog, his age and who else lives in the house, two-legged or four.
Giardia comes in several types. The ones usually found in dogs differ from the ones that make people ill, so the risk to the family is small, but it is there. Wash your hands after picking up or after bathing the dog, after playing with the puppy and before you eat. Small children stay off the patch of garden the dog uses. Anyone with a weakened immune system takes more care than the rest of the household. And if someone at home gets diarrhoea at the same time, they mention to their GP that there is a dog with giardia in the house.
For most dogs giardia is more nuisance than danger. What keeps it going for months is reinfection: cysts left in the coat, in the garden grass, on the blanket in the corner. The treatment comes from your vet. The cleaning is down to you, and if you skip it, you will be doing the treatment twice.
What dog owners search for most often on the internet about this problem, with the short answer. The answers are a guide only: the decision belongs to your dog's own vet, after an examination.
By swallowing cysts. An infected dog passes them in his stool and they survive for weeks in grass, standing water, puddles and on the coat. Another dog picks them up by sniffing, licking or drinking there, and the sick dog reinfects himself when he grooms. That is why it turns up so often in breeding and rescue kennels, boarding kennels and dog parks.
Rarely. The types usually found in dogs differ from those that make people ill, although some can cross over. Washing your hands after picking up or bathing the dog, after play and before eating keeps the risk very low. Small children and anyone with weakened immunity take extra care.
Almost always through reinfection: cysts left in the coat around the tail, in the bed, in the garden grass or on another dog at home. The bath at the end of treatment, hot-washed bedding, picking up straight away and talking to your vet about the other dogs sort out most cases. If signs persist, your vet repeats the test.
Not always. Many healthy dogs carry giardia and clear it themselves. Your own vet decides based on age, how the dog is and who else lives at home: puppies, old dogs, small children or people with weakened immunity. The cleaning is worth doing either way.
The information on this page is educational and does not replace an examination. For full details and a diagnosis, consult your dog's own veterinarian.
They often come together: the same causes, plans that complement each other.
A puddle on the carpet at five in the morning, or three days of soft stool with mucus. Two different problems, and neither one gets solved from your medicine cabinet.
A pot-bellied puppy, rice-like segments by the tail, soft stools for no clear reason. Intestinal worms are common, easy to treat and kept at bay with a schedule.
Red streaks on the stool, diarrhoea like raspberry syrup, or a black shiny stool. All of it gets called blood in the stool, but only one can be watched at home for a day.
Ten boxes on the shelf, all promising gut flora and immunity. Probiotics help dogs in a few clear situations, but they never stand in for a vet visit.
We work with your dog's behaviour, not its health. For any sign described here, book an appointment with your own vet; the related services page explains how to choose a clinic.