Prednisone is one of the most prescribed drugs in veterinary medicine, and one of the least explained. Your vet had time to cover the dose. Maybe the taper schedule. Probably not what to watch for at week three, or week twelve, or month six.
That gap is where most of the anxiety lives. Not whether prednisone works (it almost always does, and fast), but what it costs the body over time, and how you'd know if the cost is getting too high.
What prednisone is and what it treats
Prednisone is a synthetic corticosteroid that mimics cortisol, the hormone the adrenal glands produce naturally to regulate inflammation and immune response. The Merck Veterinary Manual, the reference textbook most clinicians use, covers the full mechanism in its pharmacology section. Plumb's Veterinary Drug Handbook, the dosing reference most US vets keep on their desk, lists dozens of labeled and off-label uses.
The most common: allergies, autoimmune diseases (immune-mediated hemolytic anemia, lupus), inflammatory bowel disease, lymphoma as part of chemotherapy protocols, and Addison's disease. It's also prescribed short-term for acute inflammation from injury or surgery and for respiratory conditions in both dogs and cats.
There's a distinction worth knowing. Prednisone is a prodrug. The liver converts it into prednisolone, which is the active form. In a healthy dog, the conversion is efficient and either drug works. In dogs with liver disease, vets prescribe prednisolone directly because the conversion step can't be relied on. If your dog's bottle says prednisolone instead of prednisone, everything below still applies.
The dose range is wide. A dog on prednisone for allergies might get 0.5 mg/kg once a day. A dog on immunosuppressive therapy might start at 2 mg/kg twice a day. The dose your vet set is the dose for your pet. If it doesn't match a number you read online, the bottle wins. Call the clinic and ask.
For dogs on prednisone specifically for allergies, other drug classes exist with different risk profiles. The page on Apoquel for dogs covers one of them.
The first week
Three side effects show up in almost every dog within the first few days, all dose-dependent.
Increased thirst. Your dog will drink noticeably more water. This isn't a sign something is wrong. It's a direct pharmacological effect of corticosteroids on the kidneys.
Increased urination. Follows from the thirst. Overnight accidents are common, especially in the first week. This isn't a training failure. An extra bathroom break before bed helps.
Increased appetite. Your dog will act ravenous. Some dogs become food-obsessed in ways that surprise people who've never seen it before. The appetite increase is the drug, not a real caloric need. Keep the food amount the same as before the prescription started.
Other first-week effects include restlessness, panting (especially at night), and mild GI upset. These tend to settle as the body adjusts or the dose comes down. If vomiting or diarrhea persists past the first three days, call the clinic.
The Merck Veterinary Manual describes these short-term corticosteroid effects as expected and reversible. They don't mean the drug is causing harm. They mean it's active.
What happens when prednisone stays
Short-term prednisone is straightforward. Long-term prednisone requires monitoring.
When corticosteroids are given daily for weeks or months, the body's own cortisol production slows. The adrenal glands, no longer needed at full capacity, begin to atrophy. Meanwhile, sustained exposure to synthetic cortisol affects multiple systems.
Iatrogenic Cushing's syndrome is the most common long-term consequence. “Iatrogenic” means the medication caused it. A pot-bellied appearance, thinning skin, hair loss along the flanks, and muscle wasting are the classic signs. The Merck Veterinary Manual's endocrine section covers the full presentation. Plumb's 10th edition describes it as dose-dependent and partially reversible once the taper begins.
Increased infection risk. Corticosteroids suppress the immune system. That's the point for autoimmune conditions. The tradeoff is a higher risk of urinary tract infections, skin infections, and respiratory infections. UTIs in particular can go unnoticed because prednisone already increases urination. Regular urine cultures catch them.
Steroid-induced diabetes. Sustained corticosteroid use can trigger diabetes, especially in dogs who are already predisposed. Routine bloodwork catches a rising glucose level before clinical signs appear.
Liver enzyme elevation. Prednisone reliably raises ALP (alkaline phosphatase, a liver enzyme on routine chemistry panels). This is a known pharmacological effect, not necessarily a sign of liver damage. Your vet will distinguish between the expected ALP elevation from prednisone and an elevation that means something else.
Bone and joint effects. Long-term use can weaken tendons and ligaments. In older dogs, this compounds existing mobility issues.
On the internal-medicine floor at Angell, most of the dogs I helped manage on long-term prednisone did well. But “well” meant scheduled bloodwork, urine cultures, and weight checks. The drug isn't the risk. Unmonitored use is.
Why your dog can't stop cold turkey
This is the part that catches people off guard. After more than a week or two of daily prednisone, the adrenal glands have downregulated their own cortisol production. If you stop the drug abruptly, the body has neither the external supply nor the internal one.
The result is an Addisonian crisis. Vomiting, collapse, dangerously low blood pressure. It's a genuine emergency.
A taper gives the adrenals time to restart. A common approach reduces the dose by about 25% every 5 to 7 days, but every vet adjusts for the individual dog, the condition being treated, and how long the medication has been running.
Don't adjust the taper on your own. Don't skip a dose because your dog seems better. Don't stretch the schedule faster because the side effects are frustrating. The taper your vet wrote is the one that keeps your dog safe. If you think it needs changing, call the clinic and ask.
What to track while your dog is on prednisone
A dog on prednisone for two weeks needs less monitoring than a dog on it for six months. But at any duration, six things tell the story.
Water intake. Track roughly how much your dog drinks per day. A sudden increase beyond the already-elevated baseline, especially weeks into treatment, can signal diabetes or worsening kidney function.
Urination frequency. Related to water, but worth tracking separately. A dog who's urinating every hour instead of every three is giving you data. Note whether overnight accidents are increasing or holding steady.
Weight. Weigh your dog weekly, same scale, same time of day. A gradual upward drift on the same food amount is expected in some dogs. Rapid gain concentrated in the abdomen while the legs thin is the Cushing's pattern your vet needs to know about.
Appetite and behavior. Note what changed and when. Prednisone-driven appetite increase is usually immediate and steady. A sudden appetite drop weeks into treatment is a different signal entirely.
Skin and coat. Thinning skin, hair loss along the flanks, slow wound healing, or new skin infections. These come on gradually and you miss them because you see your dog every day. Photos every two weeks, same angle, are more reliable than memory.
Bloodwork values. Your vet will run chemistry panels on a schedule. The numbers to watch: ALP (expect it elevated), glucose (screening for steroid diabetes), and kidney values if your dog is older. Ask for copies of every panel. The trajectory across three or four results tells a story that a single set of numbers can't.
If your dog is on prednisone long-term, these six things become a routine. Not a burden, a habit. Veta's pet health passport logs them across time, so when your vet asks how the last two months have been, the answer is specific, not a guess. The medication side-effect log tracks what changed and when the change started.
Questions about prednisone for dogs
Can my dog be on prednisone long-term?
Yes, but with monitoring. Some conditions require months or years on corticosteroids: immune-mediated hemolytic anemia, inflammatory bowel disease, Addison's disease. Long-term use means regular bloodwork (typically every 3 to 6 months), urine checks for infection, and weight logs. The goal is always the lowest effective dose. If your vet hasn't talked about a taper attempt, ask at the next recheck.
What's the difference between prednisone and prednisolone?
Prednisone is a prodrug. The liver converts it into prednisolone, which is the active form that does the work. In a healthy dog, the conversion is efficient and either drug works. In dogs with liver disease or significantly compromised liver function, prednisolone is prescribed directly because the conversion step can't be relied on. If your dog's bottle says prednisolone, everything in this article still applies.
How do I taper my dog off prednisone?
Follow the schedule your vet gave you. Tapering isn't optional after more than a week or two of daily use. The adrenal glands need time to restart cortisol production, and stopping abruptly can cause an Addisonian crisis: vomiting, collapse, dangerously low blood pressure. A typical taper reduces the dose by about 25% every 5 to 7 days, but your vet's schedule is the one that matters. Don't adjust it on your own.
Will prednisone make my dog gain weight?
Increased appetite is one of the most reliable short-term effects. If the food supply increases to match, weight gain follows. Weekly weigh-ins catch this early. Some of the weight is also water retention, which resolves when the dose drops. The practical move: keep the food amount the same as before the prescription started, even though your dog will act hungrier. Talk to your vet about portion size if you're unsure.
My dog is drinking and peeing constantly on prednisone. Is that normal?
Yes. Increased thirst and increased urination happen in almost every dog on corticosteroids. They're dose-dependent and start within the first few days. Accidents in the house are common, especially overnight. It isn't a behavioral problem. It's pharmacological. Keep water available and add an extra bathroom break before bed. These effects reduce as the dose tapers down.
Can I give my dog prednisone with food?
Give it with food. Corticosteroids can irritate the stomach lining, and food buffers that. Most vets prescribe it as a morning dose with breakfast. If your dog is on twice-daily dosing, pair each dose with a meal. If vomiting happens even with food, call the clinic. They may switch to prednisolone or add a gastroprotectant.
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Rachel Howland, CVT (ret.), spent a decade in clinic: seven years in a mixed practice in upstate New York, then three on the internal-medicine floor at Angell Animal Medical Center in Boston. She left practice in 2017 and has written about small-animal health since. She does not diagnose or prescribe; she explains what your vet's records are telling you and what questions are fair to ask.