If your dog is on prednisone and suddenly can’t seem to stop drinking water, it’s understandable to feel worried.
While the medication can work wonders for inflammation, allergies, or autoimmune issues, the side effects can sometimes be surprising.
We outline the common causes of excessive drinking in dogs taking prednisone, what you can do at home, and when to seek veterinary help.
Dog Prednisone Drinking a Lot of Water — Why It Happens
Increased thirst in dogs taking prednisone is a very common side effect and usually results from how the drug affects the body’s hormones and metabolism.
Prednisone acts like cortisol, a natural steroid that influences the balance of salt, water, and sugar in the body.
When your dog takes prednisone, it stimulates the kidneys to conserve sodium and excrete more water, leading to frequent drinking and urination.
However, this symptom can also overlap with other issues like diabetes, Cushing’s disease, or kidney problems.
Dog Drinking a Lot of Water and Prednisone : Common Causes
1. Steroid-Induced Polyuria and Polydipsia
Prednisone directly causes what’s known as polyuria (increased urination) and polydipsia (increased thirst).
This happens because prednisone alters how the kidneys handle water. It reduces the hormone vasopressin, which normally helps the kidneys retain water, causing your dog to lose more fluids in the urine. To balance this out, the body triggers more thirst.
Most dogs on moderate or high prednisone doses will drink significantly more water and need more frequent potty breaks.
It’s not uncommon for owners to find their dog’s water bowl empty halfway through the day or for housetrained pets to start having accidents indoors.
While this side effect is expected, it’s important to monitor how intense it becomes. If your dog’s thirst or urination seems extreme or continues after tapering off prednisone, it may signal an underlying condition.
Read more: Dog Prednisone Loose Stool (What’s normal vs. when to worry)
2. Diabetes Mellitus
Prednisone can sometimes unmask or worsen diabetes in dogs, especially with long-term use.
Because the drug mimics cortisol, it increases blood sugar levels and can make your dog’s body resistant to insulin.
Over time, this leads to glucose building up in the bloodstream and spilling into the urine, which pulls more water out of the body and causes excessive thirst and urination.
Dogs with diabetes may also show other signs like weight loss, increased appetite, or weakness despite drinking and eating normally. If your dog is on prednisone and suddenly seems ravenous yet thinner, it’s best to have their blood sugar tested promptly.
3. Cushing’s Disease (Hyperadrenocorticism)
Cushing’s disease occurs when a dog’s body produces too much cortisol — or in this case, receives it artificially through prednisone.
Because prednisone acts like cortisol, its long-term use can cause symptoms similar to Cushing’s disease. These include drinking and urinating excessively, panting, hair thinning, a pot-bellied appearance, and muscle weakness.
While these signs can be reversible once prednisone is reduced or stopped, chronic exposure can put stress on your dog’s liver and immune system. Always follow your vet’s instructions on dosage and tapering — stopping steroids suddenly can cause serious complications.
4. Kidney Problems
Excessive drinking in a dog on prednisone may not always be due to the medication alone. Kidney disease is another condition that leads to both increased thirst and urination.
The kidneys regulate water balance and waste filtration. When they start failing, they lose the ability to concentrate urine, causing more fluid loss. This prompts your dog to drink more to stay hydrated.
Prednisone can sometimes mask the early signs of kidney issues by reducing inflammation, so it’s essential to monitor lab results and urine tests if your vet prescribes long-term treatment. Persistent thirst after stopping prednisone may point to an underlying kidney problem that needs attention.
5. Urinary Tract Infection (UTI)
A urinary tract infection can make a dog drink and urinate more often, and prednisone’s immune-suppressing effect can make dogs more prone to developing one.
Because the medication lowers immune response, bacteria in the urinary tract can grow more easily. Symptoms may include cloudy urine, frequent attempts to urinate, or even accidents in the house. Sometimes, owners notice a strong urine odor or small spots of blood.
If your dog on prednisone suddenly starts urinating small amounts frequently or seems uncomfortable when peeing, a urinalysis is recommended.
Treating the infection early prevents complications and helps your dog feel better faster.
6. Prednisone Dosage or Duration
The dose and duration of prednisone treatment directly affect how severe your dog’s side effects are.
High doses or long courses of prednisone are more likely to cause excessive thirst, panting, and appetite changes. On the other hand, dogs on short-term or tapering doses often experience milder symptoms that resolve quickly once the medication is reduced.
If your dog is struggling with severe side effects, your vet might adjust the dose, change to an alternate-day schedule, or switch to a less potent steroid.
Never make dosage changes on your own — sudden withdrawal can cause adrenal crisis, which is life-threatening.
What to Do If Your Dog Is on Prednisone and Drinking a Lot of Water
First, remember that increased thirst is a normal and expected reaction to prednisone — especially during the first few weeks of treatment.
Always provide unlimited access to fresh, clean water. Restricting water to control urination can lead to dehydration and urinary tract issues. Instead, make more frequent bathroom trips part of your dog’s routine.
If your dog’s thirst seems excessive or worsens over time, talk to your vet. They may want to check kidney function, blood sugar levels, or urine concentration to ensure nothing else is contributing.
You can also ask your vet whether a lower prednisone dose or a switch to a different anti-inflammatory medication, like budesonide or cyclosporine, might help. These alternatives sometimes reduce side effects without compromising the therapeutic benefit.
At home, track your dog’s water intake and urination habits. Measuring how much water your dog drinks in a 24-hour period can give your vet valuable data. Normal water consumption for dogs is roughly 1 ounce per pound per day — anything much higher should be noted.
Finally, maintain a consistent feeding schedule and diet, and avoid giving extra salty treats, as these can worsen thirst.
When to Call or Visit Your Vet
You should contact your vet if your dog’s excessive drinking or urination:
Persists after prednisone tapering or discontinuation.
Is accompanied by vomiting, diarrhea, or loss of appetite.
Involves visible weight loss, weakness, or changes in coat quality.
Causes house accidents or your dog cannot hold urine overnight.
Is paired with signs like panting, restlessness, or abdominal swelling.
These signs could indicate complications such as diabetes, Cushing’s disease, or kidney dysfunction.
Your vet may run blood tests and urinalysis to check electrolytes, liver enzymes, and glucose levels. Adjusting the medication or addressing an underlying condition early prevents serious problems later.
Never stop prednisone suddenly, even if your dog’s side effects seem severe — this can lead to adrenal gland shutdown. Your vet will guide you through a safe tapering process if the medication needs to be reduced.
Read more: Dog Shaking on Prednisone (Why it happens and how to help)
Key Takeaway
Prednisone can be a life-saving medication, but it often comes with side effects like increased thirst and urination. Most of the time, this is harmless and improves once your dog’s dose is lowered or stopped.
However, if your dog’s thirst seems extreme, lasts long after treatment ends, or comes with other symptoms like weight loss or lethargy, it’s important to call your vet.
With regular monitoring, adequate hydration, and careful dosing, your dog can safely benefit from prednisone’s effects while minimizing unwanted side effects.
A little awareness and communication with your vet go a long way in keeping your dog healthy, comfortable, and thriving throughout treatment.