Anisocytosis: Causes and Treatments

Anisocytosis is a condition in which a patient’s red blood cells (RBCs) aren’t of equal size.

People with blood conditions, like anemia, are at a higher risk for this condition.

As you will see, when red blood cells differ in size, it can cause issues in the body. In this article, we’ll talk about common causes, as well as discuss potential treatment options.

Why Should Red Blood Cells Be the Same Size?

The main duty of the red blood cells is to transport oxygen to all the tissues of the body.

When some cells become larger than others, it can create problems. Some cells may become misshapen, which makes it harder for them to carry oxygen.

A good example is sickle cell anemia. Patients with this condition suffer from inefficient red blood cells. Thus, they feel weak and tired all the time.

While there is no cure for sickle cell anemia, there are treatment options available. These include medications, blood transfusions, and bone marrow transplants.

Bottom Line: Red blood cells carry oxygen throughout the body. If they begin to differ in size, it can lead to anisocytosis. This can lead to further complications in the body.

What Are the Symptoms of Anisocytosis?

This condition can produce many unfavorable symptoms, including:

  • Fatigue: As the red blood cells struggle to carry oxygen throughout the body, you may begin to feel tired and lethargic.
  • Pale Skin: Your skin needs oxygen like any other organ in the body. If it gets deprived, then it will start to turn pale.
  • Increased Heart Rate: As your red blood cells become less efficient, your heart will try to compensate by beating faster.

Additionally, you might feel out of breath all the time (even when sitting). These are all signs that your blood isn’t doing its job.

Notice the common theme: lack of oxygen. Red blood cells are the only cell in the body that transport oxygen.

If they stop working, no other cells can “pick up the slack”.

Since this condition can make you prone to more serious symptoms, it’s important to get them checked by a doctor.

Bottom Line: As red blood cells become more inefficient, you may become more tired and lethargic. Your skin may also turn pale.

What Causes Anisocytosis?

There are many steps to creating a red blood cell. If any of those steps become compromised, then it can cause this condition.

Here are the most common causes:

  • Vitamin B12 Deficiency: If you don’t get enough B12, then your body may produce irregular blood cells. For any vegans reading, be extra careful- you’ll need to supplement with B12 since plants don’t contain this vitamin.
  • Iron Deficiency: The “workhorse” of the red blood cells is iron. It’s what binds to the oxygen molecules and makes up the protein hemoglobin. Without sufficient dietary iron, your hemoglobin levels will drop.

Vitamin B12 is found exclusively in animal foods.

Can meat eaters be deficient in vitamin B12? Absolutely, which is why you should get your levels checked regularly.

If your body is having trouble absorbing B12 from food, your doctor may prescribe B12 injections.

Now that we’ve talked about the causes of anisocytosis, let’s look at how it’s diagnosed.

Bottom Line: Make sure that you’re getting enough dietary B12 and iron. Otherwise, you could make your RBCs less efficient.

How is Anisocytosis Diagnosed?

The most practical way to diagnose this condition is through a blood test.

After drawing a small sample of blood, a specialist can look at it under a microscope.

Here, they can determine whether the red blood cells differ in size. If the cells differ in size, then you will have one of the following:

  • +1 Anisocytosis: You have a low volume of unequally-sized RBCs. Most likely the result of low dietary iron. Often correlated with sickle cell anemia.
  • +2 Anisocytosis: You have a high volume of unequally-sized RBCs. Most likely the result of liver disease, hyperthyroidism, or vitamin deficiency.

If it’s the result of insufficient dietary iron, then it’s an easy fix: just eat more iron.

Foods rich in iron include beans, pork, red meat, dark green leafy vegetables, and peas.

If it’s the result of something more serious, then speak with your doctor about your treatment options.

Bottom Line: A blood test can determine what type of anisocytosis you’re suffering from. For instance, you can have +1 or +2.

Treatment Options

Treatment options vary depending on the root cause of your condition. There is no universal “cure” that will make it go away.

Here are a few that your doctor may try:

  • Blood Transfusion: This is generally reserved for extreme cases in which simpler treatments aren’t working. With this option, the irregularly shaped cells will get filtered out for ones that are the right size.
  • Dietary Changes: As we mentioned earlier, a simple change in your diet can help relieve the symptoms of anisocytosis. Make sure that you’re getting enough iron and B12 (vegans must supplement with B12).
  • Injections: If your body cannot adequately absorb vitamin B12, then your doctor may give you B12 infections. B12 pills are usually tried first. If those don’t work, then the injections will be necessary.

How often will you need to do these treatments? It depends on the individual. Some people may only need them once, while others may need them for life.

To avoid future episodes of anemia, pay attention to your dietary habits. Specifically, make sure that you’re getting enough B12 and iron. That will keep your red blood cells operating efficiently.

Bottom Line: The three most common treatments for anisocytosis are dietary changes (more B12 and iron), injections, and blood transfusions.


Is this condition life-threatening? No, it isn’t. However, it does signify that something more serious is happening in your body.

If you notice the symptoms, then get tested. If it turns out to be anisocytosis, then you’ll want to begin treatment immediately.

Also, remember that not all cases of fatigue are due to anemia- you could be depressed, have a thyroid issue, and more.

If you know someone who is vegan, share this article with them. It will serve as a good reminder to get more dietary iron and B12.

Ask a Question: If you want to ask a medical doctor a question that hasn't been answered in one of our articles go to: Ask a Medical Doctor About your Symptoms

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