Anemia in Cats: Signs, Causes and How Vets Judge Severity

Anemia means your cat has too few red blood cells to carry enough oxygen around the body. It is not a disease on its own but a sign that something else is going on: blood is being lost, red cells are being destroyed, or the bone marrow is not making enough of them.

The signs owners notice most are pale gums, a cat that sleeps more and plays less, and fast breathing. Any of those deserves a vet visit soon. Some deserve a phone call right now.

Call your vet now if you see these signs

• White or very pale, yellow, or brown and muddy gums
• Fast or labored breathing while your cat is resting
• Weakness, wobbliness or collapse
• Blood in vomit, black tarry stool, a nosebleed or blood in the urine
• Your cat swallowed acetaminophen (Tylenol), or ate onions, garlic or chives

If your cat is still bright but quieter than usual, or the gums look a little paler than normal, call your vet today and book an exam. Only a blood test can confirm anemia and start the search for its cause.

What is anemia in cats?

Red blood cells are made in the bone marrow and carry oxygen from the lungs to every tissue. In a cat, each one lives about 80 days before it is removed and replaced. Anemia happens when cells are lost or destroyed faster than the marrow can replace them, or when the marrow slows down.

Vets measure this with the packed cell volume (PCV), also called the hematocrit: the percentage of a blood sample made up of red cells. Cornell's Feline Health Center gives a normal PCV of about 25-45% in cats, and a PCV below 25% means the cat is anemic. Each lab sets its own reference range, so your vet's report may show slightly different numbers.

Signs of anemia in cats

Slow anemia causes vague signs; sudden blood loss causes obvious distress. Look for:

• Tiredness: sleeping more, playing less.
• Pale gums, the easiest sign for owners to spot. The inner eyelids can look pale too.
• Poor appetite and weight loss.
• Fast breathing or a fast heart rate, even at rest. A resting cat that pants or breathes with its mouth open needs a call to the vet; our guide to why cats pant covers the other causes.
• Weakness, and in severe or sudden cases, collapse.
• Yellow gums, skin or eyes (jaundice), when red cells are being destroyed.
• Eating cat litter or other odd things (pica). Uncommon, but owners do notice it.

How common are these? In one UK referral hospital study of 180 anemic cats, lethargy was recorded in 66%, poor appetite in 48% and pale gums in 48%. Jaundice showed up in 17%, and eating litter or other non-food items in only about 4%. Most anemic cats simply look tired and a bit off, which is why a gum check is worth learning.

Check your cat's gum color

Gently lift your cat's upper lip at the side of the mouth, in daylight, and look at the gum above the teeth. If the gums are naturally dark in places, ask your vet to show you a spot you can check.

A gum check tells you when to call. Your vet confirms anemia with bloodwork.

What causes anemia in cats?

Vets sort the causes into three groups, and the group tells your vet a lot about what comes next.

1. Blood loss

• Fleas, ticks, lice and intestinal worms. Fleas and ticks are a major cause of anemia, especially in kittens, and a heavily infested kitten can lose a dangerous amount of blood. Year-round parasite prevention for cats helps protect against this.
• Injury, such as being hit by a car.
• Bleeding inside the body, for example from a stomach ulcer, a tumor or a clotting problem. Black, tarry stool or blood in vomit can be a clue.
• Some rat poisons.

Slow, long-term blood loss is the usual reason a cat runs low on iron. In cats it is more often the cause than a diet short on iron, so the bleeding has to be found and stopped.

2. Red blood cells destroyed (hemolysis)

• Infections. Mycoplasma haemofelis is a tiny bacterium that attaches to red blood cells. It is the most dangerous of the feline hemoplasmas and can cause sudden, severe anemia. Feline leukemia virus (FeLV) can also trigger red cell destruction.
• Immune-mediated hemolytic anemia (IMHA), where the immune system attacks the cat's own red cells.
• Toxins. Cat hemoglobin is unusually sensitive to oxidative damage, which leaves small clumps called Heinz bodies inside the cells and gets them removed early. Acetaminophen, onions, garlic and other alliums, and zinc can all do this.

3. Not enough red blood cells made

The marrow is not producing enough new cells, so the count drifts down over weeks or months.

• Chronic kidney disease. The kidneys make erythropoietin, the hormone that tells the marrow to make red cells. Damaged kidneys make less of it, which is why anemia is common in cats with kidney disease.
• FeLV and feline immunodeficiency virus (FIV), which can damage the bone marrow.
• Long-term illness, such as chronic inflammation or cancer ("anemia of chronic disease").
• Bone marrow disease, including cancers of the marrow.

A US regional emergency: in the south-central and southeastern United States, Cytauxzoon felis, a parasite spread mainly by the lone star tick, causes a life-threatening illness in cats, with anemia in the later stages. A cat from these areas with fever, lethargy and no appetite needs a vet now.

Acetaminophen (Tylenol) is toxic to cats

Never give your cat acetaminophen or any human pain reliever unless your veterinarian has told you to. Cats lack much of the liver pathway that breaks acetaminophen down safely.

Within a few hours it turns hemoglobin into a form that cannot carry oxygen, then damages red cells and the liver. Signs include brown or muddy gums, swelling of the face or paws, trouble breathing and weakness.

Acetaminophen hides in many cold, flu, allergy and fever products. If your cat got into any, call your vet, the Pet Poison Helpline at (855) 764-7661 or the ASPCA Animal Poison Control Center at (888) 426-4435 immediately. Do not wait for signs, and do not try to treat it at home.

Onions and garlic belong on the same "never" list. Cats are more sensitive to them than dogs.

Regenerative vs non-regenerative anemia

Once anemia is confirmed, the next question is whether the bone marrow is fighting back.

• Regenerative: the marrow is working hard and releases young red cells called reticulocytes into the blood. Blood loss and red cell destruction usually cause this type, and it often improves once the cause is treated.
• Non-regenerative: the marrow is not responding. Kidney disease, FeLV and FIV, chronic illness and marrow disease cause this type.

There is one timing catch. The marrow needs about 3 to 5 days to ramp up, so a cat tested right after sudden bleeding can look non-regenerative at first, and your vet may repeat the test.

How vets judge the severity of anemia

Vets grade anemia by the PCV, but there is no single official scale. In one UK referral hospital study of 180 anemic cats (Korman and colleagues, Journal of Feline Medicine and Surgery, 2013), the cats fell into these bands:

In that study, how low the PCV was did not predict which cats survived to go home. The cause did. Cats whose red cells were being destroyed did better than cats with bone marrow problems, and cats with cancer did worse. The authors concluded that the decision to treat should not rest on severity alone.

So when your vet talks about severity, they are weighing three things:

1. The number. A very low PCV may need a transfusion before anything else.
2. How fast it fell. A sudden drop from bleeding causes more distress than the same number reached slowly over months.
3. The cause. This decides the treatment and the outlook.

Referral hospital cats are not every cat, so ask your vet what your cat's own numbers mean.

How vets diagnose anemia

The workup looks for the cause, and your vet picks the tests from your cat's history and exam. Common ones:

• Complete blood count (CBC) with PCV to confirm and grade the anemia, plus a reticulocyte count to tell regenerative from non-regenerative.
• Blood smear to look at the red cells under the microscope for Heinz bodies, parasites and young cells.
• Blood chemistry, urinalysis and a fecal test for kidney, liver and parasite problems.
• FeLV and FIV tests, and PCR for Mycoplasma, which is more sensitive than a smear.
• X-rays or ultrasound for internal bleeding or masses, and a bone marrow sample when the cause is still unclear.

If a transfusion might be needed, samples are usually taken first, because donor blood changes the results.

Treatment depends on the cause

Stabilizing first. A cat with severe or rapidly worsening anemia may need a blood transfusion, oxygen and fluids in the hospital before the cause is even known.

Blood typing matters. Cats have three blood groups: A, B and AB. Type B cats naturally carry strong antibodies against type A blood, and a mismatched transfusion can cause a severe or fatal reaction, so vets blood-type or crossmatch first.

Then the cause is treated. Your veterinarian chooses the medicines and doses. In general terms:

• Blood loss: stopping the bleeding, plus parasite control when fleas, ticks or worms are to blame.
• Mycoplasma infection: antibiotics and supportive care.
• IMHA: medicines that calm the immune system.
• Toxins: emergency care and antidotes where they exist.
• Kidney disease: managing the kidney disease; some cats also get medicines that stimulate red cell production.
• FeLV, FIV and marrow disease: supportive care, sometimes repeated transfusions.

Can you treat anemia in cats at home?

No. No home remedy, food or supplement fixes the cause, and the cause is what matters.

Iron is the tempting one, because that is what people take. But in cats, low iron mostly follows long-term blood loss, and most anemic cats are anemic for other reasons. Don't give iron, vitamins or any other supplement without your vet, and tell your vet about anything your cat already gets.

What you can do:

• Check gum color when your cat seems off, and call if it is pale, yellow or brown.
• Keep up year-round flea and tick prevention.
• Keep human medicines shut away, and onions and garlic off your cat's plate.
• Keep FeLV vaccination and testing up to date, especially for kittens and outdoor cats.
• After diagnosis, give only what your vet prescribed and keep every recheck.

Outlook: will my cat recover?

Many cats do. The outlook is good for most cats diagnosed early that are otherwise healthy, and anemia from fleas or a one-off injury often resolves once the cause is treated.

In the UK referral study, 62% of the anemic cats survived to go home. Cats with kidney-related anemia often lived a long time with ongoing care, and immune-mediated disease and younger age went with better odds.

Anemia can also be fatal: 38% of the cats in that study died or were euthanized, and causes such as Mycoplasma haemofelis can bring on severe anemia fast. The earlier the cause is found, the more options your vet has.

Questions to ask your vet

• How low is my cat's PCV, and is the marrow responding?
• Which of the three groups do you think the cause falls into?
• What tests come next, and does my cat need a transfusion?
• Which signs mean I should come back right away?

FAQ

What is a dangerously low PCV in a cat?

There is no single cutoff. A cat that looks weak, is breathing fast or has collapsed needs urgent care whatever the number.

Can anemia in cats go away on its own?

Not reliably. Once the underlying problem is treated, the red cell count often recovers; chronic causes such as kidney disease need ongoing management instead.

Is anemia in cats contagious?

Anemia itself is not, but some causes are. FeLV spreads through close contact between cats. How Mycoplasma haemofelis spreads isn't fully known: Cornell names fleas and ticks, the Merck Veterinary Manual says fighting is suspected, and it can pass in infected blood. If one cat in your home has an infectious cause, ask your vet whether the others should be tested.

Originally written by Dr. Kaylee Ferreira. Updated by the I Love Veterinary editorial team.

Sources

• Cornell Feline Health Center: Anemia
• Merck Veterinary Manual: Anemia in Cats
• Merck Veterinary Manual: Overview of Anemia in Animals
• Merck Veterinary Manual: Hemotropic Mycoplasma Infections in Animals
• Merck Veterinary Manual: Cytauxzoonosis in Cats
• Merck Veterinary Manual: Toxicoses From Human Analgesics in Animals
• Korman RM et al. A retrospective study of 180 anaemic cats: features, aetiologies and survival data. Journal of Feline Medicine and Surgery, 2013
• VCA Animal Hospitals: Anemia in Cats
• Feldman B. Feline Anemia: Practical Investigation and Management. WSAVA World Congress Proceedings, 2001 (VIN)
• Cornell Feline Health Center: Feline Leukemia Virus
• Pet Poison Helpline: Acetaminophen Is Toxic to Cats
• ASPCA: People Foods to Avoid Feeding Your Pets
• Veterinary Referral Associates: Signs and Causes of Anemia in Cats

This article is for general information and is not a substitute for advice from your veterinarian.