What Are the Side Effects of Prednisone in Dogs?

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-14

Key Takeaways

• Prednisone, a corticosteroid, mimics natural hormones to reduce inflammation and suppress the immune system, making it effective for conditions like allergies and inflammatory bowel disease.
• Common, generally manageable side effects appearing within the first 24-48 hours include increased thirst, urination, appetite, and panting, stemming from altered fluid balance and hormonal pathways.
• Serious, life-threatening side effects requiring immediate emergency veterinary intervention include collapse, difficulty breathing, vomiting blood, and black, tarry stools, indicative of severe gastrointestinal bleeding or systemic crisis.
• Other concerning signs warranting a same-day veterinary appointment include persistent vomiting, bloody or watery diarrhea, extreme lethargy, or straining to urinate, which may signal complications or underlying issues exacerbated by prednisone.
• Abrupt cessation of prednisone is dangerous, potentially causing adrenal insufficiency; gradual tapering under veterinary guidance is crucial to allow the body's natural cortisol production to recover.
• Long-term prednisone use can lead to chronic conditions such as diabetes mellitus or Cushing's syndrome, necessitating regular veterinary monitoring, including bloodwork, to detect and manage these potential sequelae.

If your dog has been prescribed prednisone, you are probably noticing some changes already. Prednisone is a corticosteroid, a type of medication that mimics hormones your dog's body makes naturally to control inflammation and calm an overactive immune system. It is highly effective for conditions like allergies, asthma, inflammatory bowel disease, and certain immune disorders. But it comes with a predictable set of side effects, and knowing what to expect can reduce your worry.

The most common side effects appear within the first few days of treatment. Your dog may drink more water, urinate more often, pant heavily, and act hungrier than usual. These effects are normal and usually manageable. However, some side effects are serious and need immediate veterinary attention. If your dog collapses, has difficulty breathing, vomits blood, or has black, tarry stools, stop reading and go to an emergency vet now. This article explains what you will likely see, what is dangerous, and how to help your dog through treatment.

Is This an Emergency?

Some side effects are alarming but harmless. Others signal a life-threatening problem. Use this table to decide your next step. When in doubt, call your veterinarian. They know your dog's history and can tell you whether a sign needs urgent care.

{
 "type": "triage",
 "title": "Urgency triage by severity of signs",
 "tiers": [
  {
   "tier": "danger",
   "label": "Go to an emergency vet now",
   "signs": [
    "Collapse, fainting, or inability to stand",
    "Difficulty breathing, including rapid breathing that does not slow down when your dog rests",
    "Vomiting blood or material that looks like coffee grounds",
    "Black, sticky, or tar-like stools"
   ],
   "action": [
    "Do not wait for an appointment",
    "Do not try home care",
    "Transport your dog to the nearest open emergency clinic immediately"
   ]
  },
  {
   "tier": "warn",
   "label": "Book a same-day appointment",
   "signs": [
    "Vomiting more than once in 12 hours",
    "Diarrhea that is watery or contains blood",
    "Extreme lethargy where your dog will not get up to eat, drink, or go outside",
    "Straining to urinate with little or no urine produced"
   ],
   "action": [
    "Call your regular veterinarian as soon as they open",
    "Describe the signs and ask for the earliest possible slot",
    "If they cannot see you today, ask which emergency clinic they recommend"
   ]
  },
  {
   "tier": "safe",
   "label": "Watch at home for 24 to 48 hours",
   "signs": [
    "Increased thirst and urination",
    "Increased appetite",
    "Panting that is mild to moderate and stops when your dog is calm and cool",
    "Mild restlessness or pacing"
   ],
   "action": [
    "These are expected effects of prednisone",
    "Monitor your dog's water intake and bathroom frequency",
    "If the panting becomes constant or your dog seems distressed, move up to a same-day appointment"
   ]
  }
 ]
}

Why Prednisone Causes These Side Effects

Prednisone works by suppressing the immune system and reducing inflammation throughout the body. That is why it helps with itchy skin, swollen joints, and inflamed bowels. But the drug does not act only on the problem area. It travels through the bloodstream and affects many organs at once.

One of the first effects is on the kidneys. Prednisone causes the kidneys to retain sodium and excrete potassium, which changes how your dog balances fluids. Your dog's body thinks it needs more water, so the thirst center in the brain gets triggered. Your dog drinks more, and the extra fluid has to leave somehow, so urination increases. This is why a dog on prednisone may ask to go outside every hour and drain the water bowl twice as fast as usual.

The increased appetite comes from the same hormonal pathway. Prednisone stimulates appetite centers in the brain, which is why many dogs on this medication act like they are starving. They may beg, steal food, or eat so fast they vomit. This effect is temporary and usually fades as the dose is tapered down.

Panting is another common effect. Prednisone can raise body temperature slightly and also affects the part of the brain that regulates breathing. Some dogs pant even when they are cool and calm. The panting is often worse in the afternoon or evening. It can be distressing to watch, but it is rarely dangerous unless it is accompanied by other signs like blue gums or collapse.

What Else Could Be Going On

The signs your dog is showing might not be from prednisone alone. Some conditions that require prednisone also cause similar symptoms. For example, Cushing's disease, a condition where the adrenal glands produce too much cortisol, causes increased thirst, urination, and panting. If your dog was already developing Cushing's disease, prednisone can make those signs much worse.

Infections can also hide behind prednisone treatment. Because the drug suppresses the immune system, a mild infection that your dog could normally fight off may become serious. If your dog develops a fever, a cough, or discharge from the eyes or nose while on prednisone, that is not a normal side effect. That is a new problem that needs veterinary attention.

Another possibility is that the dose is too high for your dog. Every dog responds differently to corticosteroids. A dose that is fine for one dog may cause severe restlessness and aggression in another. If your dog is pacing constantly, unable to settle, or acting irritable, the dose may need adjustment. Only your veterinarian can make that change. Never adjust the dose yourself, because stopping prednisone suddenly can cause a dangerous condition called adrenal insufficiency, where the body cannot produce enough cortisol on its own.

How Long Do Side Effects Last

Most side effects begin within the first 24 to 48 hours of starting the medication. They typically peak during the first week and then stabilize. If your dog is on a short course of prednisone, such as five to seven days, the side effects usually resolve within a few days after the last dose. If your dog is on a long-term course, the side effects may persist for the entire treatment period.

The key is the tapering schedule. Veterinarians usually reduce the dose gradually instead of stopping abruptly. This gives your dog's adrenal glands time to recover their natural cortisol production. Follow the tapering schedule exactly as written. Missing doses or stopping early can cause a relapse of the original condition or trigger withdrawal symptoms.

When to Call Your Veterinarian

Call your veterinarian if you are unsure whether a sign is normal. They would rather hear from you than have you wait too long. Specific reasons to call include vomiting that happens more than once, diarrhea that lasts more than 24 hours, refusal to eat for more than a day, or any sudden change in behavior like aggression or confusion.

Also call if your dog develops new symptoms that were not present when the medication started. A cough, lameness, or swelling in the face or limbs is not a prednisone side effect. It is a separate problem that needs evaluation. The FDA Center for Veterinary Medicine provides information on approved animal drugs and how to report adverse reactions, and the American Veterinary Medical Association offers guidance on working with your veterinarian about medication concerns.

Remember that prednisone is prescribed because the benefits outweigh the risks for your dog's specific condition. Most dogs tolerate it well, and the side effects are manageable with a few simple adjustments like more frequent bathroom breaks and measured meals. Your job is to observe, report, and follow the dosing instructions exactly. Your veterinarian is your partner in this treatment, and they are the only person who can safely adjust the medication.

What You Can Do at Home Right Now

If your dog is on prednisone and showing side effects, start with the basics. Offer fresh water at all times. Your dog will drink more, sometimes much more, so check the bowl several times a day and refill it. Take your dog out to urinate more often. Do not scold your dog for accidents. The medication is driving the thirst and urination, not a behavior problem.

Feed smaller meals more often if your dog is hungry all the time. Ask your veterinarian whether you can add plain canned pumpkin or green beans to help your dog feel full without adding many calories. Do not change the dose of prednisone on your own. Do not stop it suddenly. Stopping suddenly can cause a dangerous drop in natural steroid levels. Your veterinarian will tell you how to taper the dose when it is time to stop.

Do not give your dog any human medication for stomach upset, pain, or anything else. Many human drugs are toxic to dogs. Do not give supplements without asking your veterinarian first. Some supplements interact with steroids.

Watch your dog's breathing. Panting is common, but heavy, labored breathing is not. Count breaths while your dog rests. A normal resting rate is usually under 30 breaths per minute. If the rate is higher, or if your dog is struggling to breathe, that is an emergency. Go to an emergency clinic now. Do not wait for a video call.

What to Measure and Write Down

Before you call your veterinarian, gather a few facts. Write down the date you started the medication and the dose your veterinarian prescribed. Note how many times your dog urinated in the last 24 hours and whether there was blood in the urine. Track how much water your dog drinks. A rough way to measure is to fill the bowl to the same line each morning and note how much you add during the day.

Record your dog's appetite. Is your dog eating normally, ravenously, or refusing food? Note any vomiting, diarrhea, or black, tarry stools. Black stools can indicate bleeding in the stomach or intestines. That needs urgent attention. Also note any weakness, collapse, or difficulty standing. These signs can point to a serious problem called steroid-induced muscle weakness or a reaction that needs immediate care.

Side Effect Frequency Table

This table shows how common each side effect is. Every dog is different. Your dog may have none, some, or several of these.

Management Checklist for Thirst, Urination, and Appetite

Use this checklist daily while your dog is on prednisone.

• Water bowl full and fresh at all times
• Extra bathroom breaks, including one right before bed
• Note any accidents and where they happen
• Meals split into three or four smaller portions
• Ask your vet about safe low-calorie fillers if hunger is extreme
• Weigh your dog twice a week and write it down
• Watch stool color and consistency each day
• Count resting breaths once a day
• Keep a list of any new signs and when they started

What a Veterinary Visit Usually Involves

If you call about side effects, your veterinarian will ask about the dose, how long your dog has been on it, and what signs you are seeing. They may ask you to send a video of your dog's breathing or walking. They may ask you to measure water intake for a day.

For mild side effects, the visit may be a phone call or a short checkup. For more serious signs, the veterinarian will examine your dog. They may feel the abdomen to check the liver and kidneys. They may listen to the heart and lungs. They may take a blood sample to check organ function and a urine sample to look for infection. Steroids can raise liver enzymes and blood sugar. They can also hide or worsen infections.

The cost of a visit depends on your region and clinic. A simple recheck might run from 50 to 150 dollars. Bloodwork and urine testing can add 100 to 300 dollars. Emergency care costs more, often several hundred dollars or more. These are general ranges only. Prices vary widely, so ask your clinic for an estimate before testing.

When an Online Vet Can Help, and When It Cannot

Some situations in this article need hands-on care. Do not use a remote consultation for heavy or labored breathing, collapse, seizures, black stools, blood in vomit or stool, or a dog that cannot stand. These signs can be life-threatening. Go to an emergency clinic in person. A video call cannot measure your dog's temperature, listen to the lungs, or check for internal bleeding.

A remote consultation is genuinely useful for early or mild side effects. If your dog is drinking more and panting a little, an online vet can help you decide whether that is normal or worth a visit. They can also help with a recheck on a known problem, such as confirming that increased thirst is expected on the current dose. They can answer questions about whether a new sign warrants an in-person appointment.

A remote vet can take a history and look at visible signs on video. They can see your dog's breathing pattern, body condition, and behavior. They can advise on management and, in many states, prescribe medication. But they cannot palpate the abdomen, listen to the chest, take a temperature, run bloodwork, or image anything. Prescribing rules differ by state. A veterinarian may require an in-person examination before prescribing or refilling prednisone. For any sign that could mean a serious problem, an in-person exam is the only safe choice.

Common Mistakes Owners Make With Prednisone

Stopping the medication suddenly. Prednisone suppresses the body's natural steroid production. Stopping abruptly can cause weakness, vomiting, diarrhea, or a dangerous drop in blood pressure. Always taper the dose under your veterinarian's direction.

Giving the wrong dose. A missed dose is not a reason to double the next one. Giving extra can worsen side effects quickly. If you miss a dose, ask your vet what to do. The FDA emphasizes that dosing errors are a common cause of problems with pet medications.

Hiding the pill in a treat that your dog inhales. Your dog may swallow the pill without chewing it, which is fine, but you may not know if the pill was actually taken. Give the pill directly, then offer a small treat afterward.

Ignoring increased thirst and urination. These are expected, but they can also signal that the dose is too high or that diabetes has developed. Track how much water your dog drinks and how often they go out.

Assuming every new sign is from prednisone. Panting, increased thirst, and hunger are common. But vomiting, diarrhea, or straining to urinate can mean something else is happening. Do not assume. Call your vet.

How to Reduce the Chance of Side Effects Returning

The best way to reduce side effects is to use the lowest effective dose for the shortest time. Your veterinarian chooses the dose based on your dog's condition, weight, and response. Do not ask for a lower dose on your own. Instead, ask whether a lower dose is safe for the condition being treated.

Give the medication at the same time each day, usually in the morning. This mimics the body's natural steroid rhythm and may reduce nighttime restlessness and urination.

Give the pill with food to reduce stomach upset. If your dog vomits after a dose, call your vet before giving the next one.

Keep a log of side effects. Bring it to every appointment. This helps your vet adjust the dose with evidence, not guesswork.

What Recovery and Ongoing Management Usually Look Like

Recovery depends on why your dog is taking prednisone. For short courses, such as a flare of allergies or a mild inflammatory condition, side effects often fade within a few days of stopping the medication. Thirst and urination usually return to normal within one to two weeks.

For long-term use, such as for immune-mediated disease or chronic inflammation, your dog may stay on a low dose for months or years. Side effects may persist but often become less intense as the dose is lowered. Your vet will aim for the lowest dose that controls the disease.

Weight gain and muscle weakness can take weeks to reverse. A gradual return to normal exercise, with your vet's approval, helps rebuild muscle. Do not start vigorous exercise while your dog is still on a high dose, because steroids can weaken tendons and ligaments.

Some dogs develop diabetes or Cushing's syndrome from long-term steroid use. These conditions need separate treatment. Your vet will check blood work regularly to catch these problems early.

If your dog was on prednisone for a short illness, full recovery of normal energy and appetite usually happens within two to four weeks after the last dose. If your dog was on it for months, expect a slower return to normal, sometimes six to eight weeks.

Frequently Asked Questions

Can I give my dog over-the-counter prednisone? No. Prednisone is a prescription drug. Giving a human version or a leftover pet prescription is dangerous because the dose and strength may be wrong. The FDA warns that giving the wrong medication or dose is a leading cause of adverse reactions. Your veterinarian must determine the correct drug, dose, and duration for your dog's specific condition.

Why is my dog panting so much at night? Prednisone increases body heat and can cause restlessness. Panting is a direct side effect of the drug, not necessarily a sign of pain. Count breaths per minute while your dog rests. Normal is under 40. If the rate is higher, or if your dog seems distressed, call your vet. Do not assume it is just the medication.

My dog drinks a huge amount of water. Is this dangerous? Increased thirst is expected. It becomes a problem if your dog cannot drink enough, cannot reach water, or starts urinating in the house. Make fresh water available at all times. If your dog drinks more than about double their normal amount, or if urination becomes uncontrollable, contact your vet. This can signal the dose is too high.

Should I feed my dog more because they are always hungry? No. The hunger is caused by the drug, not by a real need for calories. Feeding extra leads to rapid weight gain and muscle wasting. Keep meals at the normal amount and choose low-calorie treats if you need to reward your dog. If hunger is extreme, ask your vet about adjusting the dose.

Can prednisone cause permanent damage? Long-term use can lead to diabetes, Cushing's syndrome, or weakened bones and ligaments. These are serious but often manageable with monitoring and dose adjustments. Short courses rarely cause permanent harm. The American Veterinary Medical Association advises regular checkups and blood work for pets on long-term steroids to catch problems early.

What do I do if I miss a dose? Give the missed dose as soon as you remember, unless it is almost time for the next dose. In that case, skip the missed dose and continue the normal schedule. Never give two doses at once. If you are unsure, call your veterinarian for guidance. Keep a pill organizer or set a daily alarm to reduce missed doses.

Related Clinical & Scientific Guides

• What Are the Side Effects of Bravecto for Dogs? What to Watch For
• Can You Give Your Dog Human Allergy Medicine? Whats Safe
• Can You Give Your Dog Dramamine for Car Sickness?

References and Further Reading

• FDA Center for Veterinary Medicine Animal Drug Information
• FDA Safe Use of Pet Medications
• AVMA Pet Owner Resources
• MSD Veterinary Manual Pet Owner Version
• AAHA Pet Owner Resources

Related Articles

• What Are the Side Effects of Cerenia for Dogs?
• What Are the Side Effects of Clavamox for Dogs?
• What Are the Side Effects of Gabapentin for Dogs?
• What Are the Side Effects of Trazodone for Dogs?
• What Are the Side Effects of Vetmedin for Dogs?

This article is general educational information for pet owners. It is not a substitute for veterinary diagnosis, examination, or treatment. If your pet is showing severe or rapidly worsening signs, contact an emergency veterinary hospital immediately.