Understanding pernicious anaemia: What your blood is telling you

Most people do not give much thought to their blood, unless they are undergoing a blood test or have an injury. But what people do not realise is that the blood is constantly doing amazing things to keep us running. Things like: carrying oxygen, fighting off nasty germs, and helping us heal from our cuts and bruises. So, when something changes and goes wrong, as in pernicious anaemia, the symptoms can sneak up on you.¹

What is pernicious anaemia?

Pernicious anaemia is a type of vitamin B12 deficiency. Vitamin B12 is needed in the body to make healthy blood cells and keep our nervous system running. Without enough B12, things would start to fall apart. 

There is a common misconception that Pernicious anaemia is caused by your diet, i.e., not eating enough meat, eggs, or dairy. These foods are normally targeted as they are a source of B12. But in the majority of cases, Pernicious Anaemia is caused because your body is not absorbing B12 the way it is supposed to.

The stomach makes a special protein called intrinsic factor, this protein is designed to help your body absorb vitamin B12. When you have pernicious anaemia, your immune system attacks the cells that make an intrinsic factor. So without this, the body will not absorb vitamin B12, no matter how much you eat foods rich in B12.²

Why is B12 so important, anyway?

Imagine Vitamin B12 as a key ingredient your body needs to make red blood cells. But not only this, it helps with the nervous system and keeps the brain sharp. Imagine it as being the ingredient flour when baking a cake; without it, the cake will not be cake! Similar to this, our blood without vitamin B12 will not create red blood cells that will work properly. 

In healthy people, bone marrow makes red blood cells that are small, round, and perfect for carrying oxygen from your lungs to other parts of your body. In people with pernicious anaemia, the bone marrow will make cells that are big and not fully developed; these are not great for carrying oxygen. Many of these types of red blood cells will die before they do their job.³ 

This ultimately will lead to anaemia. Anaemia is when there are not enough healthy red blood cells to deliver oxygen to your body. Meaning you will start to have symptoms like fatigue, shortness of breath, dizziness, and more.

What will happen to the blood?

Healthcare professionals will look at the blood by running tests such as a full blood count. There are telltale signs that point towards pernicious anaemia:

Macrocytic anemia 

Macrocytic anaemia is when your blood cells are larger than usual. This may not seem like a big deal, but size matters here. Big red blood cells will not be able to travel through tiny blood vessels efficiently. They are more fragile and will die quickly.⁴

In a blood test, you will see:

• A high Mean corpuscular volume (MCV). MCV. Check how big, on average, your red blood cells are. In pernicious anaemia, this value will be high
• Low red blood cell count
• Low  hemoglobin
• You may see low levels of white blood cells and platelets, too

Megaloblastic changes in the bone marrow

This will show up if a healthcare professional decides to look at how red blood cells are being made in the bone marrow. Immature red blood cells (called megaloblasts) will look strange. The nuclei (control centre for cells) will not be developing properly. They do not develop properly because the DNA in the nuclei cannot be made properly, as there is not enough B12. What this means is the cell is trying to grow, but something is stopping it from turning out right. The Results? Big, misshapen cells that will not be able to carry oxygen like they should.⁵

Other signs we may see in a blood test

Pernicious anaemia doesn’t just mess with the red blood cells.  It could also lower your white blood cells and platelets, which means your immune system and blood clotting would take a hit.⁶

In a blood test, you may see the following changes:

• High LDH (lactate Dehydrogenase) - this will rise when a lot of cells are breaking down
• Elevated indirect bilirubin - A sign that red blood cells are being destroyed at a faster rate than is normal
• Low B12 levels - this should not surprise anyone that a healthcare professional will check this first
• High levels of methylmalonic acid and homocysteine - this increases when B12 is low, and will confirm a diagnosis
• Positive intrinsic factor antibodies - a likely indicator of pernicious anaemia

What would a blood smear show?

Healthcare professionals might decide to do something called a peripheral blood smear. This is where a professional will look at blood in a slide under a microscope. They might see:

• Macro-ovalocytes - These are large, oval-shaped red blood cells. This is a sign that the red blood cell has not developed properly
• Hypersegmented Neutrophils - This is a type of white blood cell that normally has more than 5 segments in its nucleus (centre control for the cell)
• Anisocytosis and poikilocytosis - this is when the red blood cells vary in size and shape more than usual

All together, these signs will be a big hint that something is wrong with the absorption of vitamin B12. 

Could it be something else? 

Yes, other conditions may cause red blood cells to become large. Healthcare professionals will do a differential diagnosis and order the correct tests.

Other common conditions that present similarly: 

• Folate deficiency 
• Liver disease 
• Alcohol use 
• Certain medications (such as chemotherapy medicines and epilepsy medicines)
• Bone marrow disorders

Healthcare professionals will look at the full picture, such as your symptoms, lab results, and your medical history, before diagnosing you.⁷

Good news: It’s treatable 

Once someone has been diagnosed with pernicious anaemia, it is usually straightforward to treat. 

Since your body cannot absorb Vitamin B12 naturally. You will likely need B12 injections - normally every few weeks at the beginning. These will skip going into the stomach and will be injected directly into your muscle. Some people may choose to have a high dose of B12 pills instead, but the injection tends to work much faster and more reliably. 

Most people report that they feel so much better within a few weeks of starting treatment; they report having more energy, less fatigue, and being able to think more clearly. Blood cell production begins to return to normal, and symptoms will return. 

An important thing to note is that if B12 deficiency goes untreated for too long, nerve damage can happen, and may not fully reverse with treatment. This is why early diagnosis is imperative.⁸

Summary 

Sometimes, the first signs that something’s wrong in your body show up in your blood. That’s the case with pernicious anaemia, a condition where your red blood cells are too big and not fully developed. This happens because your body doesn’t have enough vitamin B12, which is essential for making healthy blood cells.

The reason for the B12 shortage isn’t always about what you eat. In pernicious anaemia, it’s often caused by an autoimmune problem. The body starts attacking the stomach cells that produce something called intrinsic factor, a protein that’s needed to absorb B12 from food. Without that, no matter how much B12 you take in, your body can’t use it properly.

As a result, the bone marrow starts making red blood cells that are larger than normal and not very effective at carrying oxygen. You might feel tired, weak, dizzy, or even notice things like numbness in your hands and feet. Some people also experience memory issues or mood changes, which are linked to how important B12 is for the nervous system.

These kinds of changes in the blood, especially large, immature red blood cells and certain patterns seen under a microscope, are strong clues for doctors. They help pinpoint pernicious anaemia and separate it from other types of anaemia.

It’s a condition that can fly under the radar at first, but your body often gives subtle signs. If something feels off for a while and there’s no clear explanation, checking your B12 levels might be a good next step. The blood often tells the story before anything else does.