Side Effects Of Injectable and Oral Steroids In Cats

A cat at a vet's office ready to receive injectable or inhalable steroids.

Side Effects Of Injectable and Oral Steroids In Cats

This article is part of our Cat Asthma series. 

Download the Full Guide to Cat Asthma

Oral and injectable steroids are commonly prescribed to treat certain conditions in cats. However, the problem with these oral steroid medications is that they can have many potential side effects. As a result, using these medications long-term isn’t recommended.

What Are Oral And Injectable Steroids?

Oral corticosteroids (often called oral steroids) are medications taken by mouth in either liquid or pill form to reduce inflammation. Injectable steroids are similar but are delivered through a needle. These synthetic corticosteroid medications are meant to resemble a hormone naturally produced in the body called cortisol.1 Cortisol’s main function is to break down sugars and reduce swelling and inflammation.

Unlike anabolic steroids that increase muscle mass (like in human bodybuilding and sports), corticosteroids are considered catabolic steroids— they help lower inflammation and, in higher doses, suppress the body’s immune system.2

 A cat at the vet's office being administered injectable steroids 

What Are Steroids Used For In Cats?

Steroid medications are commonly used to treat a variety of conditions in cats, ranging from inflammatory conditions to conditions where the immune system is overactive and the body begins to attack normal, healthy cells. Depending on the severity and nature of the condition, the treatment dose will differ.

Some inflammatory conditions steroid medications are used to treat include:

  • Asthma
  • Other Respiratory Conditions
  • Allergies
  • Dermatitis

In higher doses, corticosteroid medications are used to treat overactive immune system (immune-mediated) conditions such as:

  • Inflammatory Bowel Disease (IBS)
  • Hyperactive immune system
  • Polyarthritis
  • Meningitis
  • Haemolytic anaemia
  • Other immune-mediated conditions3

Steroids and their anti-inflammatory properties play an important role in respiratory disease management. They help prevent asthma attacks by suppressing inflammation in the airways which otherwise causes swelling and airway blockages. Inflammation is one of the hallmarks of asthma and chronic bronchitis and requires regular steroid use for the life of the pet to keep it under control. However, oral and injectable steroids can cause health side effects when used regularly. To mitigate side effects, a preferred alternative to injectable or oral steroids is an inhaled steroid medication. (jump ahead to Oral Vs. Inhaled Steroids)

Types Of Systemic Steroid Medications For Cats

Although there are several other forms of corticosteroid medications (such as inhaled and injected), the main types of oral steroids prescribed for cats include:

  • Prednisone
  • Prednisolone
  • Dexamethasone

Injected options include depo-medrol (Pfizer, methylprednisone) and dexamethasone.

These corticosteroids are synthetic and much more potent than steroids naturally occurring in the body and typically last much longer. This combination of strength and length of time that they are active in the body is what can cause the serious side effects when used long term.

The Difference Between Prednisone And Prednisolone

While both have similar effects, prednisolone is the metabolized form of prednisone. Prednisone must be metabolized by the liver before it can be used effectively. Cats are not able to absorb and convert prednisone into the active metabolite, prednisolone. This means there is a higher bioavailability of prednisolone—it is absorbed at a higher rate and degree than prednisone.4 Unfortunately, both forms can still cause unwanted side effects.

 A cat being examined at a vet's office for side effects of oral steroids.


What Are The Side Effects Of Oral Steroids In Cats?

Oral and injectable medications need to be processed by the body. Once in the bloodstream, they spread throughout the entire body system. Only some of the medication goes to the intended target, the rest could impact other organs as well.

This is why these types of medications are often referred to as systemic steroids. As such, there are many side effects associated with oral and injected steroid use.

Short-term side effects are expected soon after a cat begins to take oral and injected corticosteroids. These effects will vary by dose. Long-term side effects are seen over time if a cat has been prescribed long-term treatment with oral corticosteroids. The severity of these effects depends on the dose and duration of treatment.

Side Effects Of Prednisone, Prednisolone, And Dexamethasone In Cats

As prednisone, prednisolone, and dexamethasone are all oral corticosteroids, they have similar short-term and long-term side effects in cats.

Short-term effects of oral corticosteroids:

  • Loss of energy
  • Increased risk of infection
  • Increased thirst and appetite
  • Weight gain
  • Vomiting
  • Diarrhea
  • Panting
  • Frequent urination

Long-term effects of oral corticosteroids:

  • Lethargy/fatigue (no energy to play)
  • Change in behaviour (such as aggression)
  • Suppressed immune system function
  • Increased risk of bacterial/fungal infections
  • Increased risk of urinary tract infections
  • Poor wound healing
  • Stomach ulcers
  • Diabetes
  • Weight gain / obesity
  • Impaired wound healing
  • Cushing’s disease
  • Loss of bladder control
  • Hair loss
  • Increased blood pressure
  • Allergic reaction
  • Skin or coat changes5

 A cat happily yawning and stretching.


These side effects may reduce the quality of life of not only the affected cat, but also the family relationship. Cats who are lethargic or have a change in behaviour may be unable or unwilling to play and may no longer seem like the cat you knew.

Can Cats Be On Oral Or Injected Steroid Medications Long-Term?

In the case of feline asthma, systemic steroids may be used by a vet during an asthma attack. However, because of the many side effects of using oral steroids, they should not be used for long-term disease control.

The goal of systemic steroids is often to get an immediate respiratory response if the cat is in distress. The cat can then be transitioned to inhaled steroids for regular management. According to Plumb’s Veterinary Medication Guides 6, the goal of oral steroid treatment is to find the lowest dose possible and use it for the shortest period of time. For chronic conditions that require ongoing treatment, this becomes problematic.

Oral Vs. Inhaled Steroids For Cats With Asthma: Why Inhaled Steroids Are Considered Safe And Effective

Because cat asthma and chronic bronchitis are life long conditions, corticosteroids are an important part of daily disease management to keep the airways clear and help cats with these conditions live a normal life.

Inhaled corticosteroids are a safer alternative to oral and injectable steroids, lacking the side effects that can be common to systemic steroids. Inhaled steroids are designed to be used on an ongoing basis for inflammation and symptom control without exposing the cat to the risks of systemic medications. There are two key differences between inhaled and systemic steroids that make them safer:

1. Inhaled Steroids Target The Lungs Directly

Inhaled corticosteroids target the lungs and airways directly. Unlike systemic steroids where only some of the drug reaches the lungs (and the rest is spread throughout the body), inhaled steroids go directly to the active site where they are needed.

2. Inhaled Steroids Require A Much Lower Dose

Because Inhaled steroids target the lungs directly, the concentration of steroid can be much less. Systemic steroids have to be given in much higher concentrations to ensure that an appropriate dose reaches the airways after first being metabolized and then indiscriminately sent throughout the body.

Using a substantially lower dose to achieve the same therapeutic effect can significantly lower the risk of harmful side effects.

 A cat being administered steroids in pill form.


Keep Your Pet Safe Long-Term

The typical goals of asthma management are risk reduction and symptom control. According to the Global Initiative for Asthma (GINA)7, the intent of management is to reduce the burden to the patient and to reduce their risk of asthma-related death, exacerbations, airway damage, and medication side-effects.

In human children with asthma, inhaled steroids are considered the gold standard treatment for long term disease management. Systemic steroids are not recommended for daily asthma control. And, just like for children, inhaled steroids are considered safe and effective for cats and are a better option for the management of respiratory conditions.8

For cat owners, being informed about the side effects of injected and oral corticosteroid use is the first step in ensuring your cat is safe and healthy. Always be on the lookout for any side effects your cat may be showing after starting these medications.

Before starting your cat on oral steroids or if you are interested in transitioning away from systemic steroids, talk with your vet about using inhaled corticosteroid medications instead, and how the AeroKat* chamber can help manage your cat’s condition.


This article is part of our Cat Asthma series. 

Download the Full Guide to Cat Asthma

1 Brooks, W., DVM, Veterinary Partner, "Prednisolone/Prednisone" (

2 Brooks, W., DVM, Veterinary Partner, "Prednisolone/Prednisone" (

3 Willows General Practice Service, "Steroid Therapy" (…)

4 Canna-Pet, "Side Effects of Prednisone for Cats" (

5 Hunter, T., DVM, VCA Hospitals, "Steroid Treatment Long Term Effects in Cats" (…)

6 Plumb's Veterinary, "Prednisolone/Prednisone Medication Guide" (…)

7 Global Initiative For Asthma, "Global Strategy for Asthma Management and Prevention" (…)

8 Padrid, P., DVM, "Inhaled Steroids to Treat Feline Lower Airway Disease: 300 Cases 1995-2007" (…)