SIBO in dogs, or small intestinal bacterial overgrowth, is when too many bacteria, or the wrong mix, build up in the small intestine. It usually causes chronic watery diarrhoea, wind and weight loss despite a good appetite. Vets treat it by finding the underlying cause, with antibiotics, a highly digestible diet and vitamin B12 where needed.
Owners often wonder why a dog's digestive problems keep coming back despite several food changes. Switching diets can help, but chronic diarrhoea or weight loss sometimes comes from a deeper bacterial imbalance in the gut. If your dog has a sensitive stomach that never settles, understanding SIBO is a helpful step towards a long-term plan.
What is SIBO in dogs, and how does it differ from ARD?
SIBO is an abnormal increase in bacterial numbers, or a shift in the types of bacteria, in the small intestine. This disrupts normal digestion and absorption. The bacteria are not always "bad" ones. They are often just in the wrong place, in the wrong numbers.
You may also hear the term antibiotic-responsive diarrhoea, or ARD. It is seen particularly in German Shepherds, where an inherited tendency may play a part. ARD describes dogs whose diarrhoea settles on antibiotics. Many relapse once the medicine stops if the underlying cause is not addressed, which is why a longer-term plan matters.
The gut does not work in isolation either. Its link with stress and behaviour is covered in our guide to the gut-brain axis in dogs.
What are the symptoms of SIBO in dogs?
The main symptom of SIBO in dogs is chronic, watery diarrhoea that keeps coming back despite diet changes. Many owners notice their dog seems fine for a few days before the cycle starts again.
SIBO poop tends to be loose, large in volume and sometimes greasy or pale, because food is not being absorbed properly. Straining, lots of mucus or fresh blood point more towards the large bowel, so mention exactly what you see to your vet.
Alongside loose stools, you might notice wind or loud gas and gurgling stomach sounds. These are common signs that the small intestine is struggling.
Weight loss, even with a normal or bigger appetite, is a significant warning sign. Some dogs also have a dull coat or seem low in energy.
These signs are not specific to SIBO. They overlap with conditions such as IBD in dogs, so your vet will need to run tests to rule other problems in or out.
What causes SIBO in dogs?
SIBO in dogs is usually caused by another problem that lets bacteria build up in the small intestine. Common underlying causes include exocrine pancreatic insufficiency (EPI), where the pancreas does not make enough digestive enzymes, and slow gut movement.
Undigested food left in the gut feeds the bacteria, which is why SIBO is common in dogs with EPI. Other gut diseases, previous surgery and, in some breeds such as German Shepherds, an inherited tendency can also play a part.
SIBO is not contagious. It is an overgrowth of the dog's own gut bacteria, not an infection caught from another dog.
How do UK vets diagnose SIBO in dogs?
UK vets diagnose SIBO by ruling out other causes and looking for typical changes in blood tests. There is no simple, perfect SIBO test for dogs. The most direct method involves taking samples from the small intestine during an endoscopy, but that is invasive and expensive.
Instead, vets often start by checking folate and cobalamin (vitamin B12) in the blood. Bacteria in the small intestine can make folate and use up B12, so a high folate with a low B12 can point towards overgrowth. These tests help but are not definitive on their own.
Finding the root cause is essential. Your vet may test pancreatic function to rule out EPI, check a poo sample for parasites and run wider blood tests. The results shape the treatment and diet plan.
How is SIBO in dogs treated?
SIBO in dogs is treated by tackling the underlying cause, reducing the bacterial overgrowth and supporting digestion. A course of antibiotics is often used first to bring bacterial numbers down. On its own, though, it rarely gives a lasting fix.
A highly digestible diet is a cornerstone of management. Food that is absorbed quickly leaves less behind in the small intestine to feed the bacteria.
Cobalamin (B12) supplements are also vital when levels are low, because the overgrown bacteria compete with the dog for this vitamin. Injections are often used at first, and oral tablets can work well for long-term support. Your vet will recheck levels over time.
If EPI is the cause, enzyme powder added to every meal is essential, and the SIBO often improves once digestion is corrected. Treatment takes patience. Give any plan several weeks of consistency before judging whether the gut has settled.
Can SIBO in dogs be treated naturally? A common myth is that a "natural" remedy or a change of probiotic alone can cure it. In my view as an MRCVS-registered vet, diet and gut support help a lot, but SIBO needs a proper diagnosis and usually some medical treatment, especially when there is an underlying cause such as EPI.
Can diet and probiotics help manage SIBO in dogs?
Yes, diet and gut support can help manage SIBO in dogs, alongside your vet's treatment. A dog SIBO diet focuses on highly digestible food that leaves little behind to fuel the overgrowth. Your vet may suggest a prescription gastrointestinal diet.
Probiotics for SIBO are less straightforward. Adding more bacteria to an overgrowth needs thought, so talk to your vet before starting one. Our review of whether probiotics for dogs work covers the evidence more broadly.
Once your vet has the overgrowth under control, daily gut support can help keep things steady. Juno Daily for gut health includes Calsporin® Bacillus velezensis, a spore-forming probiotic that survives stomach acid, plus postbiotics, which are deliberately not alive, and prebiotic fibres. If you are not sure what your dog needs, the Juno supplement quiz is a sensible place to start, ideally after a chat with your vet.
These supplements support balance. They are not a cure for structural problems in the gut or for EPI.
How do you manage recurrent SIBO in dogs long term?
You manage recurrent SIBO in dogs with consistency: an easily digested diet, regular B12 checks and prompt treatment of the underlying cause. Long-term success comes from routine rather than quick fixes.
Gut problems often overlap with other conditions, so your vet may also look at links such as dog allergies and gut health to get the whole picture.
Stress can affect gut movement and make flare-ups more likely. A calm, predictable routine, regular meals and gentle exercise all help. Keep a simple diary of stools, appetite and weight so you can spot a relapse early.
Key takeaway: SIBO is usually a sign of another problem, so the best long-term results come from treating the cause, not just the diarrhoea.
If your dog's tummy troubles keep coming back, push for answers rather than another food change. Once your vet has a plan in place, Juno Daily is an easy way to add steady daily gut support. And if your dog loses weight, stops eating or seems very flat, book a vet check straight away.
Frequently asked questions
Is SIBO in dogs contagious?
No. SIBO is an overgrowth of the dog's own gut bacteria, usually because of another problem such as EPI or slow gut movement. It cannot be caught from another dog, though infections that cause diarrhoea can be, so your vet may still check for them.
What is the best dog SIBO diet?
A highly digestible diet, often a prescription gastrointestinal food, works best for most dogs. Feed regular meals, avoid sudden changes and rich extras, and ask your vet before switching. Some dogs do well on a low-fat recipe too.
How do vets test for SIBO in dogs?
There is no single perfect test. Vets usually check folate and vitamin B12 in the blood, rule out EPI and parasites, and sometimes take samples from the small intestine during an endoscopy. A response to treatment also helps confirm it.
Can SIBO happen in dogs with EPI?
Yes, it is common. In EPI, food is not digested properly, and the leftovers feed bacteria in the small intestine. Treating the EPI with enzyme powder at every meal often helps the SIBO settle too.
Are probiotics good for dogs with SIBO?
They can help some dogs once the overgrowth is controlled, but adding bacteria to an overgrowth needs care. Talk to your vet first, and choose a product made for dogs with named strains and clear amounts.
Can SIBO in dogs be cured?
Many dogs do very well once the underlying cause is treated, and some never relapse. Others, especially those with inherited forms, need long-term management with diet, B12 and occasional treatment of flare-ups.
What does SIBO dog poop look like?
Usually loose or watery, larger than normal and sometimes greasy or pale, because food is not being absorbed well. Fresh blood, lots of mucus or straining suggest a large bowel problem instead, so describe what you see to your vet.
How long does SIBO treatment take to work in dogs?
Some dogs improve within days of starting treatment, but it usually takes several weeks of steady diet and treatment to judge properly. Recheck B12 levels as your vet advises, and report any relapse early.
This guide is for informational purposes only and does not constitute veterinary advice. Always consult your vet before making changes to your dog's diet, supplement routine, or healthcare plan.
