When your dog starts having loose stool while on prednisone, it can be confusing and worrying. You might wonder whether the medication is helping or causing more problems than it solves.
We outline the common causes of loose stool in dogs taking prednisone, what you can do at home, and when to seek veterinary help.
Dog Prednisone Loose Stool — Why It Happens
Loose stool in dogs taking prednisone usually develops because of how this steroid affects the digestive system and metabolism. Prednisone can irritate the gastrointestinal lining, change the gut microbiome, and increase stomach acid, all of which make digestion less stable.
It may also indirectly cause diarrhea or softer stool by affecting appetite, water intake, and the immune system. Some dogs have sensitive stomachs and react strongly to prednisone even at standard doses.
In other cases, the loose stool may not be from the medication itself but from the underlying disease being treated or a secondary infection that developed because prednisone suppresses immune function.
Dog Loose Stool and Prednisone: Common Causes
1. Gastrointestinal Irritation from Prednisone
Prednisone is a corticosteroid that can be harsh on the digestive tract. It increases acid production and decreases the protective mucus in the stomach and intestines.
As a result, your dog’s gut lining becomes more vulnerable to irritation, leading to softer stool or mild diarrhea. Some dogs also show signs like burping, flatulence, or a gurgling stomach.
If the loose stool is mild and your dog otherwise seems fine, it’s often a sign of minor irritation.
However, persistent diarrhea may indicate that prednisone is too harsh for your dog’s stomach or needs to be taken with food or stomach protectants prescribed by your vet.
Read more: Dog Diarrhea After Prednisone (Understanding this common side effect)
2. Changes in Gut Bacteria Balance
Prednisone alters the immune system and can disturb the balance of beneficial bacteria in the gut.
When the microbiome shifts, digestion becomes less stable, and the stool may become loose or more frequent. Some dogs may even develop secondary bacterial overgrowth, which worsens the stool consistency and produces a stronger odor.
This imbalance can take time to correct, even after stopping the medication. Your vet might suggest probiotics to help restore normal gut flora during or after prednisone treatment.
3. Increased Water Intake and Appetite
One of the most well-known side effects of prednisone is increased thirst and hunger.
When your dog drinks more water and eats more food than usual, it can put stress on the digestive system. The stomach may not process large meals efficiently, and the intestines may move waste faster than normal, resulting in loose stool.
This cause is common in dogs who were previously on a strict feeding routine but now can’t stop begging for food or water while taking prednisone. Adjusting feeding frequency and portion size can often help in these cases.
4. Immune Suppression and Secondary Infections
Because prednisone suppresses the immune system, it can make dogs more prone to infections, including bacterial or parasitic infections in the gut.
When these infections occur, loose stool, mucus in stool, or diarrhea are common symptoms. You might also notice vomiting, lethargy, or weight loss.
If your dog’s stool contains blood, looks greasy, or has a foul smell, it’s essential to contact your veterinarian. Stool testing can identify if an infection is contributing to the loose stool.
5. Underlying Condition Being Treated
Sometimes, the reason for loose stool isn’t prednisone itself—it’s the condition prednisone was prescribed to treat.
Dogs with inflammatory bowel disease, liver disease, or certain cancers may already have digestive issues. Prednisone can temporarily worsen these problems before stabilizing them.
If your dog’s loose stool began before starting prednisone and is continuing, the medication may not be the root cause but could still be complicating the symptoms.
6. Long-Term or High-Dose Prednisone Use
Dogs that have been on prednisone for extended periods or at high doses are at higher risk for side effects, including gastrointestinal upset.
Prolonged use can thin the stomach lining, alter metabolism, and make digestion more sensitive. These dogs may also experience other symptoms like panting, bloating, or muscle weakness.
If your dog has been on prednisone for weeks or months, any change in stool quality should be discussed with your vet to ensure the dosage and duration are still appropriate.
Read more: Dog Throwing Up on Prednisone (Is it normal?)
What to Do If Your Dog Has Loose Stool While On Prednisone
If your dog’s stool has become loose while taking prednisone, stay calm—this side effect is often manageable.
Start by making sure your dog stays hydrated. Loose stool can lead to fluid loss, so provide plenty of fresh water and monitor your dog’s drinking habits. You can also add a bit of low-sodium chicken broth or an electrolyte solution approved by your vet to encourage fluid intake.
Feed a bland diet for a few days, such as boiled chicken and white rice, to ease digestive strain. Avoid fatty or high-fiber foods until the stool normalizes. Smaller, more frequent meals are easier on the gut and help prevent further irritation.
Never stop prednisone suddenly without veterinary guidance. Abrupt withdrawal can cause dangerous hormonal imbalances. Instead, speak with your vet about whether the dosage should be reduced or if your dog needs an antacid, probiotic, or stomach protectant alongside the medication.
You can also discuss alternative anti-inflammatory options with your vet if the loose stool persists.
Some dogs tolerate prednisolone (a similar steroid that’s gentler on the liver) or other immune-modulating drugs better than prednisone.
When to Call or Visit Your Vet
You should contact your veterinarian promptly if your dog’s loose stool lasts more than a few days, becomes watery, or is accompanied by other symptoms.
Watch for warning signs like blood or mucus in the stool, vomiting, dehydration, or lethargy. These can indicate more serious complications such as gastrointestinal bleeding, pancreatitis, or an infection made worse by prednisone’s immune suppression.
If your dog is refusing food or water, acting weak, or seems uncomfortable, it’s time for a veterinary visit. Your vet may run bloodwork, fecal tests, or adjust the medication to find a safer balance.
In some cases, your vet may prescribe stomach protectants (like omeprazole or sucralfate), probiotics, or dietary adjustments to stabilize your dog’s digestion while continuing treatment.
Read more: Dog Very Hungry on Prednisone (Why it may happen)
Key Takeaway
Loose stool in dogs taking prednisone is one of the more common digestive side effects of this medication. While it can be messy and concerning, it’s often manageable with careful diet adjustments, hydration, and veterinary guidance.
Never adjust or stop prednisone on your own—sudden withdrawal can be dangerous. Instead, work closely with your vet to identify whether the loose stool is due to the medication, the underlying condition, or another issue entirely.
With supportive care and the right medical plan, most dogs recover quickly and continue benefiting from prednisone’s therapeutic effects without ongoing stomach upset.