Published by: Ingrid King. Last Updated on: June 29, 2023 by Crystal Uys


Immune-mediated hemolytic anemia is a condition where the cat’s immune system turns against itself and attacks the patient’s own red blood cells. The immune system’s antibodies (blood proteins that are designed to counteract substances the body recognizes as alien, such as viruses and bacteria) target red blood cells for destruction. When too many red blood cells are destroyed, the patient becomes anemic.

Symptoms of IMHA

Your cat may be lethargic and weak. She may have lost interest in food. Her gums may be pale, or jaundiced (yellow tinged). You may also notice a yellow tinge to the whites of her eyes. Urine may be dark orange or even brown. She may have a fever. You may notice an increased heart and respiratory rate. In advanced cases, your cat may collapse.

Diagnosis of IMHA

Your cat’s veterinarian will conduct a thorough physical exam and run a number of blood tests. These tests will include a complete blood chemistry and blood count, a PCV (packed cell volume) test to measure the percentage of blood which is occupied by red blood cells, a Coombs test to detect the presence of antibodies, and a blood smear (red blood cells clumped together will be an indicator of IMHA.) Other blood tests may be indicated to look for indications of infection or parasites. Your vet may also take x-rays to look for tumors and to rule out other underlying conditions.

Veterinarian doctors analyzing blood samples of cat in laboratory under microscope
Image Credit: Kzenon, Shutterstock

Treatment of IMHA

Treatment and your cat’s prognosis will depend on the underlying cause of IMHA. When possible, the underlying disease process needs to be treated. Other treatment may include supportive care, such as intravenous fluids.

Corticosteroids are an important part of treatment, as they suppress the immune system. Patients are likely to be on high doses of corticosteroids for weeks or months before the dose is tapered down. Your cat will need to be monitored with regular blood tests during treatment. Many IMHA patients will need to always be on a low dose to prevent recurrence.

If the red blood cells have dropped to critically low levels, your cat will need a blood transfusion. Transfusions with artificial blood may be a better choice than real blood for IMHA patients, since it won’t further stimulate the patient’s already compromised immune system. The downside of artificial blood is that it won’t last as long in the body, but it can buy enough time until a compatible blood donor is found.

What Causes IMHA?

IMHA in cats is most commonly caused by either the feline leukemia virus or an infection with a red blood cell parasite called hemobartonella felis. IMHA can also be caused by drug side effects, toxins, or cancer.

IMHA is a serious condition with a high mortality rate. Patients are often unstable, and treatment can be lengthy and costly. Cats who are susceptible to IMH may have recurrences months of years into the future.

Featured Image Credit: Pencil case, Shutterstock

This article was previously published on and is republished with permission.

About the author