High red blood cell count: what it means and what to do

A high red blood cell count usually does not mean a blood disease. If your haemoglobin is normal and your red cells are small, it often means you carry thalassaemia trait, which is inherited and common in Italy. If haemoglobin and haematocrit are high too, too little water, smoking or testosterone is more often behind it.

What high red blood cells mean

It means there are more red cells in your blood than usual. But the number alone is not enough: how big they are (MCV) and how much haemoglobin they carry matter too.

There are two different situations. In the first, the red cells are many but small, and haemoglobin is normal or slightly low: often an inherited trait. In the second, haemoglobin and haematocrit rise too.

In that second case haematocrit decides, because it shows better whether there really are too many red cells. Often the blood is just more concentrated, from too little water.

What causes high red blood cells

The first applies to people with small red cells. The others apply when haemoglobin and haematocrit are high too.

Symptoms

Usually none. People with thalassaemia trait usually feel fine, and often find out by chance, on a blood test.

When there really are too many red cells the blood is thicker, and headaches, dizziness or a very red face can appear. Strong itching after a hot shower is rare, but tell your doctor.

High red blood cells and low MCV: thalassaemia trait

This is the typical pattern of thalassaemia trait: many red cells, but small, with normal or slightly low haemoglobin. In Italy many people carry it, and it is also called Mediterranean anaemia.

It is easy to mistake for iron deficiency, because there too the red cells are small. The difference: with too little iron the count usually drops and ferritin is low. With thalassaemia trait the count is normal or high, and ferritin is usually normal.

It is usually confirmed by haemoglobin electrophoresis, a test that separates the types of haemoglobin, which your doctor can ask for. Thalassaemia trait usually needs no treatment, and iron does not help unless you are short of it. But it is worth knowing, including so your partner can be checked if you are planning a pregnancy.

Which tests to read alongside them

These tests help show which of the two situations is yours.

What your result means

The upper end of the scale, in x10¹²/L. If they are high, check your MCV and haematocrit too.

What to do if they are high

It depends on the cause, and the first step is finding out which. Where to start:

When to worry

Talk to your doctor if:

With Rosa, a haematocrit above 52% in men or 48% in women is always flagged to a doctor, above 56% urgently.

Frequently asked questions

High red blood cells and normal haemoglobin: what does it mean? Often it means many small red cells: check your MCV. If it is low and your ferritin is normal, it points to thalassaemia trait. Your doctor can confirm it with haemoglobin electrophoresis.

Slightly high red blood cells: should I worry? Usually not, if your haematocrit is below 52% in men or 48% in women. Too little water or an inherited trait that causes no problems is often behind it. Show your report to your doctor, who decides whether to repeat the test.

Are high red blood cells dangerous? Not by themselves: they are a signal. If there really are too many for a long time, the blood gets thicker and the risk of clots can rise. That is why a high haematocrit needs a doctor’s care.

Do high red blood cells mean polycythaemia? Usually not: polycythaemia vera is a rare bone marrow disease. Far more often too little water, smoking, testosterone or an inherited trait is behind it. If your haematocrit stays high, your doctor looks for the reason.

Do smokers have more red blood cells? Often, yes. Smoking takes oxygen away from your blood, and your body makes up for it with more red cells. Stopping usually brings the number down.

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