Steroids for cats: what to know when they are first prescribed
"I'm going to prescribe a steroid." Many owners flinch at that sentence, because the human side effects come to mind first: weight gain, bones, diabetes. Yet steroids are among the most commonly prescribed drugs in feline practice (Lowe 2008), and cats are a species that tolerates them better than dogs or people.
This is the first article in a series. It covers what the drug is, why cats are different, how to read the dose, and which diseases it is used for, with study numbers. Tapering, side effects, forms and other diseases each get their own article.
- When steroids are first prescribed: what they are and why cats tolerate them (you are here)
- Dosing and tapering: from tablet maths to the last dose
- Side effects: diabetes, heart and liver, and when to check what
- Injections, tablets, inhalers and creams: the form is half the story
- When there is another disease: heart, diabetes, kidneys, infection
- Cats have about half the glucocorticoid receptors of dogs, and they bind less tightly (liver 23 vs 45 fmol/mg, van den Broek 1992). So the same mg/kg causes fewer side effects, but cats also need higher doses than dogs.
- The oral drug should be prednisolone. Prednisone gives blood levels of only about a quarter (11-cat crossover, Center 2013).
- Doses come in two tiers: anti-inflammatory about 0.5-1 mg/kg/day and immunosuppressive about 2-4 mg/kg/day. For a 4 kg cat, 2 mg/kg is 8 mg a day, about 1.5 tablets of 5 mg.
- Calculate on ideal body weight. Overweight cats had about twice the blood level at the same mg/kg (Center 2013).
- The side effects to watch are diabetes (9.7% of 143 cats on high doses for over 3 weeks, 12 of 14 within 3 months, Nerhagen 2021) and heart failure in cats with hidden heart disease (article 3).
- Do not stop abruptly. Just 16 days at 2 mg/kg suppressed the adrenal response (Middleton 1987). Tapering is article 2.
| Who | Decides |
|---|---|
| At home | Giving the exact dose at a fixed time, noting ideal weight, tracking water, urine clumps, appetite and sleeping breathing rate, recording relapse signs during a taper |
| Together | How fast to taper and in what steps, dates for glucose and fructosamine checks, tablet vs injection vs inhaler |
| The clinic | Diagnosis (ruling out infection and cancer first), starting dose, whether to add another immunosuppressant |
- Open-mouth breathing at rest, or a sleeping breathing rate of 40 or more per minute: this can be heart failure (watch closely in the first 2 weeks, article 3).
- A sudden several-fold rise in drinking and urine with weakness or vomiting: possible steroid diabetes or ketoacidosis.
- Sudden loss of the hind legs with crying out: a clot, seen in cats with heart disease.
1. What a steroid is
The precise name is glucocorticoid. These drugs are stronger, longer-acting versions of cortisol, the hormone the adrenal glands make every day. They are not the muscle-building "anabolic steroids".
They do two jobs. At low doses they switch off inflammation (itch, cough, gut inflammation). At high doses they suppress the immune response itself (diseases where the immune system attacks the body). That is why one drug is used for allergy, bowel disease and lymphoma.
2. Why cats "tolerate" steroids
The evidence comes from receptor studies. A steroid has to bind a receptor inside the cell to work. Cat liver and skin had about half the receptors of dogs, and they bound less strongly (van den Broek 1992).
| Dog | Cat | |
|---|---|---|
| Liver receptors (fmol/mg protein) | 45 | 23 |
| Skin receptors | 46 | 24 |
| Dissociation constant Kd (nM, higher = weaker binding), liver | 0.4 | 3.2 |
Two things follow. (1) At the same mg/kg, cats get fewer side effects than dogs. (2) Cats need a higher mg/kg for the effect. Iatrogenic Cushing's from long-term use is common in dogs but so rare in cats that only 2 feline cases had been published by 2001 (Ferasin 2001). A series of 12 cats followed from Taiwan (Lien 2006).
But "tolerates" does not mean "no side effects". In cats the problems are blood glucose and the heart. In a 56-day trial of immunosuppressive doses (prednisolone 4.4 mg/kg), all 14 cats had glycogen in the liver, and glucose, triglycerides and cholesterol rose (Lowe 2008 Vet Rec).
3. Why it should be prednisolone
Prednisone is a prodrug: the liver has to convert it to prednisolone. People and dogs do this well. Cats do not.
- At the same 2 mg/kg, prednisolone gave about 4 times the blood exposure (AUC) of prednisone (11 healthy cats, crossover, Center 2013).
- Feline pemphigus used to be treated with prednisone at up to 8 mg/kg. With prednisolone, 2 mg/kg put 97% of 37 cats into complete remission within 8 weeks (Simpson 2013).
Many cats get human prednisolone 5 mg tablets split into pieces, or a compounded version from the clinic. If your cat was given a different steroid, this table shows how many mg of prednisolone it equals.
| Drug | Common forms | Equal to prednisolone 5 mg | Duration |
|---|---|---|---|
| Prednisolone | 5 mg tablet, compounded liquid | 5 mg | Intermediate (12-36 h) |
| Methylprednisolone | 4 mg tablet (Medrol etc.), long-acting injection (Depo-Medrol etc.) | 4 mg | Intermediate (injection: weeks) |
| Triamcinolone | Injection, cream | 4 mg | Intermediate (injection: weeks) |
| Dexamethasone | Injection, tablet | 0.75 mg | Long (36-54 h) |
| Hydrocortisone | Cream, injection | 20 mg | Short |
These are standard human pharmacology equivalents. A cat study treated prednisolone 4.4 mg/kg and dexamethasone 0.55 mg/kg (8 to 1) as equipotent (Lowe 2009).
4. Reading the dose: anti-inflammatory vs immunosuppressive
Divide the prescribed mg by body weight and you can see which tier your cat is on.
| Tier | Usual starting range | 4 kg cat per day | In 5 mg tablets | Typical diseases |
|---|---|---|---|---|
| Anti-inflammatory | 0.5-1 mg/kg/day | 2-4 mg | 1/2 to 3/4 | Allergic skin, asthma maintenance, mild gut inflammation |
| Immunosuppressive | 2-4 mg/kg/day | 8-16 mg | 1.5 to 3 | Severe IBD, pemphigus, immune-mediated anaemia, lymphoma |
| Maintenance | Lowest effective dose, often every other day | e.g. 1.25-2.5 mg every other day | 1/4 to 1/2 | After the taper |
Real studies give a feel for these numbers. A study of allergic cats used 1 and 2 mg/kg as "anti-inflammatory" doses (Khelik 2019). A lower-airway study averaged 1.8 mg/kg (Cocayne 2011). A high-dose cohort used a starting dose of 1.9 mg/kg or more as its cut-off, with a median of 3.0 mg/kg (Nerhagen 2021).
- 1. Set the ideal weight. For an overweight cat this is "the weight when slim", not today's weight.
- 2. Prescribed mg / ideal weight = mg/kg. Find the tier in the table above.
- 3. Example: 5.5 kg today, ideal 4.5 kg, prescribed 10 mg (two 5 mg tablets). 10 / 4.5 = 2.2 mg/kg, the immunosuppressive tier. Dividing by today's weight gives 1.8, which looks lower, but the body's exposure tracks ideal weight more closely (overweight cats had about twice the blood level, Center 2013).
- 4. If the maths calls for less than a quarter tablet (1.25 mg), ask for a compounded tablet or liquid rather than splitting.
5. Which diseases, and what the numbers say
| Disease | Where steroids fit | Study numbers |
|---|---|---|
| IBD / chronic enteropathy | After a diet trial. Many cats improve on diet alone | Of 55 cats with chronic gut signs, 29% were food-sensitive and another 20% resolved on the elimination diet: about half improved on diet (Guilford 2001) |
| Low-grade lymphoma | Prednisolone plus chlorambucil is the standard pairing | 41 cats: 56% complete and 39% partial response, median survival 704 days (Kiselow 2008). 17 cats: 76% complete remission (Lingard 2009) |
| Asthma / chronic bronchitis | Oral or inhaled (article 4) | In a 9-cat randomised trial both oral and inhaled steroids normalised signs (Verschoor-Kirss 2021). Systematic review: good evidence (Mueller 2021) |
| Allergic skin (atopic) | First-line, alongside ciclosporin | A 66-paper systematic review rated only systemic steroids and ciclosporin as "good evidence" (Mueller 2021) |
| Pemphigus | Start at immunosuppressive doses | 2 mg/kg: 97% remission, median maintenance 1.2 mg/kg/week, 14% eventually stopped the drug (Simpson 2013) |
| Immune-mediated anaemia (IMHA) | Immunosuppressive doses | 58 of 143 cats on high-dose steroids had IMHA (Nerhagen 2021) |
| Stomatitis / eosinophilic granuloma | Symptom control, alongside treating the cause (e.g. extractions) | Few controlled cat studies |
6. Where opinions differ
6-1. Can you taper as soon as the signs are gone?
Why it divides people: side effects build up with time, which argues for tapering fast. But inflammation can outlast the symptoms. In 10 cats with lower-airway disease, airway washes taken once all signs had resolved still showed inflammation in 7 (Cocayne 2011).
Our view: keep the starting dose for about 2 more weeks after the signs are gone, then start tapering, and check for relapse with records at each step (article 2).
Checking it in your cat: at each step down, record the relapse numbers (vomits, coughs, time spent licking, weight) for 2 weeks and compare.
6-2. Morning or evening?
Why it divides people: in people cortisol peaks in the morning, so morning dosing is standard. Some argue cats, being nocturnal, should be dosed in the evening, but studies of the feline cortisol rhythm have not been consistent.
Our view: the same time every day, with food, matters more than the clock. It reduces stomach upset, and the best time is the one you will never miss.
7. What the CatLab app records show
As of November 2026, 7 cats in the CatLab app have steroid medication logs. Of 437 logged doses written in mg, 93% were 1.25 mg or 2.5 mg, a quarter or half of a 5 mg tablet (the rest were 3.75 mg, three quarters). For a 3-4 kg cat that is 0.3-0.8 mg/kg, the maintenance-to-anti-inflammatory tier. Cats on steroids long term tend to end up at these low doses.
Logging the steroid in the app keeps "on steroids" next to every blood test result. Steroids change liver values, glucose and white cells, so that context matters (article 3).
8. What to bring to the clinic
- Ideal weight and current weight, so the dose is calculated on the same basis.
- Previous glucose, fructosamine and urine glucose results, as a baseline for later changes.
- Any heart murmur or heart tests. These change the form (tablet vs injection) and the monitoring plan (article 5).
- Whether a diet trial was done (for gut or skin disease): how many weeks, which protein.
- Relapse records: vomiting, coughing and itching as numbers.
9. Read next
- Article 2 · Dosing and tapering
- Article 3 · Side effects
- Article 4 · Injections, tablets, inhalers and creams
- Article 5 · When there is another disease
- Inflammatory bowel disease (IBD)
📌 One-line tip: divide the prescribed mg by ideal weight. Knowing whether your cat is on the anti-inflammatory tier (0.5-1) or the immunosuppressive tier (2-4) tells you how careful the taper and the monitoring need to be.