Steroids in cats with another disease: heart disease, diabetes, kidney disease and infection
Cats that need steroids often already have another disease, especially older cats. A cat with gut inflammation may also have heart disease, an asthmatic cat may be diabetic, a cat with lymphoma may have kidney disease. Owners in this position hear both "you can't use steroids" and "you have to use steroids".
The conclusion of this article: another disease does not rule steroids out. Instead, the form, dose and monitoring are adjusted to the disease. Below, disease by disease: what the worry is, what to change, and what to watch at home.
- When steroids are first prescribed: what they are and why cats tolerate them
- 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 (you are here)
- Heart disease (HCM etc.): avoid long-acting injections and use the lowest tablet dose. Count the sleeping breathing rate daily for the first 2 weeks. Even 5-7 days of tablets enlarged the left atrium (1.26 to 1.38 cm, Block 2020).
- Diabetes: starting or raising a steroid increases insulin needs, and reducing or stopping it can make the same insulin dose cause hypoglycaemia. Check glucose at home more often in any week the steroid dose changes. Avoid dexamethasone.
- Kidney disease: on steroids, creatinine can look lower (Sharkey 2007, Leal 2022). More drinking and urine can tip the cat into dehydration. Blood pressure did not change in short-term studies (Khelik 2019).
- Infection and viruses: urinary bacterial infection did not increase (Lockwood 2018), but antiviral defence weakened in experiments (persistent leukaemia virus infection 82% vs 11%, Rojko 1979). Watch for herpes flare-ups.
- Do not combine with NSAIDs (meloxicam, robenacoxib etc.). Leave a gap when switching.
- There are ways to need less steroid: diet (about half of gut-inflammation cats improved on diet alone, Guilford 2001), inhalers (asthma), ciclosporin (allergy), chlorambucil (lymphoma, IBD).
| Who | Decides |
|---|---|
| At home | Sleeping breathing rate (heart), home glucose and urine glucose (diabetes), water intake, fluid schedule and weight (kidneys), sneezing and eye discharge (herpes), a full medication list |
| Together | Steroid form (tablet, inhaler), insulin adjustment plan, baseline tests before starting (NT-proBNP, fructosamine, SDMA), other drugs to spare the steroid |
| The clinic | Diagnosing and treating heart failure, diabetes and infection, adding immunosuppressants, judging drug interactions |
1. At a glance, by disease
| Other disease | The worry | What to change | What to watch at home |
|---|---|---|---|
| HCM / heart disease | Heart failure from plasma volume expansion (Ployngam 2006, Block 2020) | No long-acting injections; lowest tablet dose; inhaler for asthma | Sleeping breathing rate (daily for 2 weeks) |
| Diabetes | More insulin resistance (Leal 2022); hypoglycaemia during taper | No dexamethasone; frequent glucose in dose-change weeks; no long-acting injections | Home glucose, urine ketones |
| Kidney disease | Misleading creatinine, dehydration from urine loss, muscle loss | Mark "on steroids" when reading tests; review fluid schedule | Water intake, weight, subcutaneous fluids |
| Obesity / pre-diabetes | About twice the blood level at the same mg/kg (Center 2013) | Dose on ideal weight | Urine glucose strips |
| Herpes, FIV, FeLV | Viral reactivation, weaker defence (Rojko 1979) | Lowest possible dose; care when combining immunosuppressants | Sneezing, eye discharge, mouth ulcers |
| Arthritis and other pain | With NSAIDs: gut bleeding and kidney injury | Stop the NSAID with a gap; other pain relief | Black stools, vomiting |
2. With heart disease
Steroids are risky for cats with heart disease because of the sequence in article 3. Glucose rises, plasma volume expands (+13.4% after a long-acting injection, over 40% in 3 cats, Ployngam 2006), and a thickened heart cannot cope. Even 5-7 days of tablets enlarged the left atrium and ventricle, and NT-proBNP rose more than 60% in 6 of 10 cats (Block 2020).
In cats with normal hearts, though, 1 and 2 mg/kg for 7 days made no meaningful difference to blood pressure or echocardiography (Khelik 2019). In other words, the risk is set more by the heart than by the drug.
- Before starting: if there is no recent echo, at least an NT-proBNP. A pre-treatment value for the same cat is needed to see the change (Block 2020).
- Form: avoid long-acting injections. Use an inhaler for asthma and the lowest tablet dose for gut or skin disease.
- First 2 weeks: sleeping breathing rate daily. Call if it runs 5-10 above usual or over 30 for several days; go the same day at 40 or more (resting breathing rate).
- On a diuretic (furosemide)? Agree in advance how to adjust it if the breathing rate rises (heart failure manual).
3. With diabetes
Steroids make the body respond less to insulin. After a single 20 mg long-acting injection, glucose and insulin were up at day 15 in every group (Leal 2022). So when a diabetic cat starts a steroid, the same insulin dose leaves glucose higher.
The opposite direction needs even more care. If insulin was raised because of a steroid and the steroid is then reduced or stopped, the insulin can suddenly be too much, causing hypoglycaemia. Steroids are such a large variable in glucose control that diabetic remission studies exclude cats on ongoing steroids from their analysis.
- In any week the steroid dose changes (start, increase, decrease, stop), measure glucose at home more often than usual. If you have a continuous glucose monitor (CGM), this is when it pays off most (measuring glucose at home).
- On the morning of a dose reduction, always check pre-insulin glucose. If it is lower than usual, discuss adjusting the insulin.
- Avoid dexamethasone. At equal potency it leaned more towards diabetes than prednisolone (Lowe 2009).
- For asthma, an inhaler is especially useful. Fructosamine did not change over 8 weeks of inhaled fluticasone (Verschoor-Kirss 2021).
- Diabetes caused by steroids may resolve as the drug is reduced or stopped (transient diabetes in 4 of 12 cats, Lien 2006). That makes watching for hypoglycaemia during the taper even more important.
4. With kidney disease
- Misleading creatinine: creatinine fell after a single long-acting injection (Sharkey 2007, Leal 2022). If creatinine improves on steroids, the kidneys may not have improved. Read it with SDMA and urine specific gravity from the same time, and note "on steroids" beside the results (reading creatinine).
- Muscle loss: steroids break down muscle protein, and thigh muscle wasting has been reported with long-term use (Lien 2006). Less muscle makes creatinine look even lower. Record weight and muscle score together.
- More drinking and urine: a cat with kidney disease can slip into dehydration quickly. If your cat gets subcutaneous fluids, check weight and skin turgor after starting to see whether the fluid volume is still right.
- Blood pressure: short-term oral studies found no change (median 145 to 145 mmHg, Block 2020; Khelik 2019). Cats on blood pressure medication should still be measured once 2-4 weeks after starting.
- A bigger appetite can be a plus for a kidney cat. Point it at the renal diet so protein and phosphorus control stays on track.
5. With infection or viruses
In dogs, long-term steroids increase urinary bacterial infection. In cats, 0 of 32 on long-term treatment had a positive culture (1 of 34 healthy controls, Lockwood 2018). That is reassuring.
Viruses are different. In an experiment, cats given long-acting injections and then exposed to feline leukaemia virus (FeLV) became persistently infected in 82% (18 of 22), compared with 11% (1 of 9) of untreated cats (Rojko 1979). It is an experimental setting, but it shows steroids can weaken antiviral defence.
- Herpes carriers: sneezing, eye discharge or eye rubbing during steroid treatment may be reactivation. Steroid eye drops can worsen herpes keratitis (article 4).
- FIV- or FeLV-positive cats sometimes need steroids, for stomatitis for example. Use the lowest dose and avoid stacking immunosuppressants.
- Unexplained fever or diarrhoea: the rule is to rule out infection (especially parasites and bacterial enteritis) first. Steroids can mask infection and delay diagnosis.
6. Combining with other drugs
| Drug | Combined, it means | How |
|---|---|---|
| NSAIDs (meloxicam, robenacoxib) | Added risk of gut ulcers, bleeding and kidney injury | Do not combine. Leave a gap when switching (evidence from dogs and people; we found no direct cat study) |
| Ciclosporin | Added immunosuppression | A combination used to spare the steroid. Watch for infection |
| Chlorambucil | Standard pairing for lymphoma and severe IBD | 41 cats with low-grade lymphoma: 56% complete, 39% partial response (Kiselow 2008). Regular blood counts |
| Insulin | Higher needs; hypoglycaemia during taper | Frequent glucose in dose-change weeks (section 3) |
| Diuretics | Overlapping fluid and electrolyte shifts | For heart cats, an adjustment plan based on breathing rate (section 2) |
| Vaccines | Response may be weaker at immunosuppressive doses | Discuss timing vaccines outside the high-dose period |
7. Ways to need less steroid
With another disease present, using steroids at lower doses and for shorter periods pays off. Each disease has options that can replace or accompany the steroid.
| Disease | What spares the steroid | Evidence |
|---|---|---|
| IBD / chronic enteropathy | Hydrolysed or novel-protein diet trial (first) | About half of 55 cats improved on diet alone (Guilford 2001) |
| Asthma | Inhaled steroid | Few systemic effects (Reinero 2006). Good evidence in a systematic review (Mueller 2021) |
| Allergic skin | Ciclosporin | With steroids, the only "good evidence" option in a systematic review (Mueller 2021) |
| Lymphoma / severe IBD | Chlorambucil | Kiselow 2008 |
| Pemphigus | Finding the lowest maintenance dose (alternate days, weekly totals) | Median maintenance 1.2 mg/kg per week (Simpson 2013) |
8. Where opinions differ
Why it divides people: some say steroids should "never" be given to cats with heart disease, citing a case series of 12 cats with sudden heart failure after steroids (Smith 2004, not available online) and the plasma volume study (Ployngam 2006). Others point out that short courses changed nothing in cats with normal hearts (Khelik 2019) and that heart failure was under 1% in 1,042 cats given long-acting injections (Dutch 2023).
Our view: not "never", but "change the form and the monitoring". Leaving lymphoma, immune-mediated anaemia or severe IBD untreated is also a large risk. The tools are the lowest tablet dose instead of long-acting injections, an inhaler where possible, and the sleeping breathing rate for the first 2 weeks.
Checking it in your cat: a pre-treatment NT-proBNP or echo plus a daily breathing rate lets you judge from records whether this dose is all right for this cat.
9. What to bring to the clinic
- Every medication and supplement (including painkillers, insulin, diuretics and eye drops). Showing the app medication log is enough.
- Baselines for each disease: NT-proBNP or echo dates for heart disease, recent glucose curve and fructosamine for diabetes, SDMA, urine specific gravity and blood pressure for kidney disease.
- The steroid dose-change schedule, so insulin and diuretic changes line up with it.
- Any history of herpes, FIV or FeLV.
10. Read next
- Article 1 · When steroids are first prescribed
- Article 2 · Dosing and tapering
- Article 3 · Side effects
- Article 4 · Injections, tablets, inhalers and creams
- HCM Bible · When another disease comes too
- Diabetes Bible · When another disease comes too
- CKD Bible · Comorbidities
📌 One-line tip: for a cat with another disease, mark every steroid dose-change day on the calendar and measure that disease's numbers (breathing rate, glucose, weight) more often that week.