IMHA Toolkit
Clinical protocols & thrombosis prevention awareness
IMHA Survival Rates & Prognosis
Survival statistics for immune-mediated haemolytic anaemia vary considerably between studies and cannot predict the outcome for an individual animal. This page explains what published studies tell us about short- and long-term survival in dogs, cats and horses, and why the numbers need careful interpretation.
Canine IMHA is a serious disease, particularly during the acute phase, but survival figures are not uniformly poor. A large British multicentre study reported 74% survival to hospital discharge [Goggs et al., 2015], while a more recent Irish cohort reported 87% [Duclos et al., 2024]. Dogs that survive the first few months can subsequently have prolonged survival.
What does an IMHA survival rate actually mean?
Published survival figures describe groups of patients treated in particular hospitals, during particular periods, using particular inclusion criteria. They do not provide a precise probability for an individual dog, cat or horse.
Studies may measure different endpoints. One may report survival to hospital discharge, another survival at 30 days or one year, while another reports median survival time. Comparing these figures as though they measure the same thing can be misleading.
Prognosis should be based on the individual patient's clinical condition and response to treatment, not on a single percentage found online.
Canine IMHA survival
Canine IMHA remains a potentially life-threatening disease, but modern referral-hospital studies show that a substantial proportion of affected dogs survive the initial hospitalisation.
In the Irish study, dogs with non-associative IMHA had mortality rates of 16% at one month and 31% at three months. Among dogs that survived beyond three months and did not have an identified associative condition, median survival was 2,664 days — approximately 7.3 years [Duclos et al., 2024].
That long-term figure is particularly important for owners. It does not mean that every dog surviving three months can expect another seven years of life. It does show that the initial diagnosis of IMHA should not automatically be interpreted as implying a short remaining lifespan once the acute disease has been successfully controlled.
Why is the early phase so dangerous?
Severe anaemia itself can be life-threatening, and some dogs fail to respond adequately to immunosuppressive treatment. IMHA is also associated with a markedly increased risk of thrombosis.
Current ACVIM guidance describes thrombotic disease as a leading cause of morbidity and mortality in canine IMHA and recommends thromboprophylaxis for affected dogs unless severe thrombocytopenia or another contraindication makes treatment inappropriate [Swann et al., 2019].
This does not mean that any particular antithrombotic drug has been proved to increase survival in every IMHA patient. The optimal antithrombotic strategy remains an area where the evidence is incomplete. Learn more about why blood clots develop in IMHA →
What affects prognosis in dogs?
No single blood result or clinical finding can reliably predict whether an individual dog will survive. Studies have, however, identified factors associated with a less favourable outcome [Duclos et al., 2024]:
- Higher bilirubin concentrations or marked jaundice
- Thrombocytopenia
- Evidence of kidney dysfunction, including increased urea or creatinine in some cohorts
- Greater overall illness severity
- Development of serious complications such as thromboembolism
- Poor or inadequate response to treatment
These are prognostic associations, not certainty. A dog with one or more adverse indicators may still recover, while apparently favourable initial results cannot guarantee an uncomplicated course.
Feline IMHA survival
IMHA is less common in cats than in dogs, and feline studies include relatively small and sometimes clinically diverse populations. It is therefore particularly important not to present one percentage as a universal feline survival rate.
In a Royal Veterinary College retrospective study of 107 cats with IMHA, 72 were classified as having primary IMHA and 35 had secondary IMHA associated with another disease. Cats with primary IMHA had substantially better long-term outcomes than cats with secondary IMHA [Swann et al., 2016].
The cause associated with the anaemia can therefore be highly important when discussing prognosis in cats. A newer 2026 retrospective cohort of 37 cats with non-associative IMHA found that 32/37 (86.5%) survived to discharge and overall mortality was 24.3%, with all deaths occurring within the first four weeks. Five cats relapsed and only two achieved sustained treatment-free remission during follow-up. The study therefore supports a comparatively favourable acute survival rate while also showing that prolonged immunosuppression and relapse can remain important clinical issues [Kulmer et al., 2026].
Equine IMHA survival
Immune-mediated haemolytic disease is uncommon in adult horses, so the published evidence is much smaller than the canine literature.
One retrospective study examined 25 adult equids with immune-mediated haemolytic anaemia, immune-mediated thrombocytopenia or both. Fifteen of the 25 survived to discharge. Outcome differed markedly according to whether the immune-mediated disease was classified as primary or secondary [Easton-Jones et al., 2021].
Neoplasia was more common among affected equids than controls, and secondary immune-mediated disease was associated with a poorer short-term outcome.
Neonatal isoerythrolysis in foals is an alloimmune disease caused by maternal antibodies against the foal's red blood cells. It is clinically important, but it should not be pooled with adult autoimmune IMHA when presenting survival statistics.
Frequently asked questions
What is the survival rate for dogs with IMHA? ▼
There is no single survival percentage that applies to every dog. A large British multicentre study reported 74% survival to discharge, while a more recent Irish referral-hospital cohort reported 87%. Differences in patient population, severity, diagnostic criteria and treatment mean that these figures cannot be used as an exact prediction for an individual dog.
What is the life expectancy of a dog that survives IMHA? ▼
Dogs that survive the acute phase can have substantial long-term survival. In one recent retrospective study, dogs with non-associative IMHA that survived beyond the first three months had a median survival time of 2,664 days, or about 7.3 years. That is a population statistic rather than an expected lifespan for an individual dog.
When is IMHA most dangerous? ▼
The early acute phase is particularly important because severe anaemia, inadequate treatment response and complications such as thromboembolism can become life-threatening. Dogs that stabilise and survive the first few months may subsequently have a much more favourable long-term outlook.
What factors affect a dog's prognosis with IMHA? ▼
Prognosis depends on the dog's overall illness severity, response to treatment, bilirubin and other laboratory findings, organ function, platelet count, thromboembolic complications and whether another disease is associated with the IMHA. No single measurement reliably predicts an individual dog's outcome.
Do blood clots affect survival in dogs with IMHA? ▼
Yes. Thromboembolic disease is a recognised major complication of canine IMHA and contributes to morbidity and mortality. This is why current consensus guidance includes thromboprophylaxis as an important component of canine IMHA management unless contraindicated.
The Key Message
IMHA is most dangerous during its acute phase, but dogs that respond to treatment and survive the first few months can go on to have prolonged survival.
Reading Survival Studies
- Check which species was studied.
- Check whether disease was primary or associated with another condition.
- Look at the endpoint: discharge, 30 days, one year or median survival.
- Do not apply a population percentage directly to one patient.
Continue Learning
Survival statistics make more sense when viewed alongside the treatment journey, clotting risk and possibility of relapse.
Evidence & Interpretation
Canine data: survival and prognostic figures on this page draw principally on the British multicentre IMHA registry, the more recent Irish retrospective cohort and the ACVIM consensus treatment statement.
Feline and equine data: evidence is based on substantially smaller retrospective populations and should therefore be interpreted particularly cautiously.
Open the IMHA Toolkit Evidence Library →