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.

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.

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

14 Comments on What Is IMHA and How Did My Cat Get It?

  1. Hi.

    Thank you for this post.

    Unfortunately our little kitten seem to have the worst luck getting this disease. We have had him since he was 4 months old and he started showing symptoms when he was about 8-9 years.

    It has been a roller coaster. Into the vet hospital with a PCV of 9 and they were astonished that he was alive. He had to be in the icu for two days and in the hospital for a total of 5 days. It was a mess for us.

    He got better and better with medications so the vet decided to stop and a relapse came a few weeks after.

    He is now 2 years, 1 month old and he is on his third relapse. We rushed him into the animal hospital and he has been in the icu for a day now. After icu he was put at the normal area. He sleeps a lot and is very tired. At lowest his PCV was 7 and today it was 8.

    They moved him back to the icu today as they wanted to get extra eyes on him. They also gave him some pain medication as he wasn’t happy being handled so much. Poor boy has been at hospitals whole his life.

    We have accepted the fact that he might pass and it is heartbreaking. We hope to get him stable again so that we medicate him for the rest of his life as he was himself while on the meds.

  2. My cat was diagnosed with it. Just sudden change in behavior, 11 years old no medical problems prior. He had transfusion and got his counts up and steroids with mycophenolate. The vet wanted to taper his dose from 15mg of prednisolone daily to 12.5mg prednisolone daily when he was at PCV of 30 holding well since the original bout. 2 weeks later, his PCV is down to 16. Today I have him in the hospital getting a transfusion and steroids. Praying he survives.

    I never encountered this disease before. I warn you, it is very scary. The liquid medications with the animals spitting them up makes me wonder if they actually getting the meds at the appropriate dose. My cat would gag and spit up a little bit.

    Keep this in mind with the medications. I wish everyone the best of luck if their pet is diagnosed with this. I am typing this with tears in my eyes as I pray he makes it through the night.

  3. My 7 year old male cat has primary IMHA. He was diagnosed in January, 2016, and this has been a roller coaster ride for all of us. He has had numerous recurrances and each time it gets harder to push into remission. He currently has it full blown, his HCT/PCV is only 9.2 and the vet doesn’t understand how he’s still alive. He is having Dexamethasone shots and we pray they will work again. This is a horrible, unpredictable disease and I wonder often if we’re doing the right thing with the shots, vet visits, labs, etc. His quality of life isn’t good most of the time. It is heartbreaking to watch and deal with.

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