What is a normal blood count?

Please Note – This website provides information about cancer, most people have blood tests at some point in their lifes and most people do not have cancer. Blood tests are non-specific, that means they can be used to check for a whole range of different illnesses, not just cancer. In fact very few cancers can be diagnosed by looking at blood test results.

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If you are having chemo you will probably have a lot of blood tests (and a lot of questions)

Remember, a blood test on it’s own probably doesn’t mean all that much, when trying to work out what a blood test means, your doctors need to think about how much chemo you have already had and where in the cycle of chemo you are (i.e. how much chemo you have had in total and how recently you’ve had it)  They also look at the results of other tests (for example, scans) to decide if they need to do anything about an “abnormal” result.  Quite often blood test results can vary from week to week, we are humans, not machines, so this is normal!  Your doctors will also look at how your results have changed over several months.

But just what is a normal blood test result?

There are many different types of blood test; the results below are from a white blood cell count on a normal woman.  A reference range is very important, this tells you what you would expect to see in a normal result.  It is normal for the reference range to vary between hospitals and laboratories, it often depends which particular machine or method was used to count the cells. In order to understand a blood test you need to know the reference range used by the laboratory that did the test. The reference ranges given below are from a UK hospital.

Or to put it another way, in a drop of blood about this size • (1 cubic millimetre or 1 microlitre) there are about 8, 000 white blood cells and 211, 000 platelets.

Usually a blood test will tell you what types of white blood cell are present, so in the results above there are 6,700 neutrophils, 700 lymphocytes, 420 monocytes, 260 eosinophils and 20 basophils in that tiny drop.

Another way to look at a normal  white blood cell count, is to draw a graph, of the average numbers of cells in an average person.  This sort of graph has large “error bars”, this doesn’t mean the graph is wrong, just that people are different.  The graph below shows the averages for a normal adult, but remember, these numbers are averages and your normal value might be higher or lower than the numbers on the graph and that is fine.

Graph showing average values for a normal adult white blood cell count

So, in a normal blood test about 60 % (or a little under two-thirds) of the white blood cells should be neutrophils. Lymphocytes should make up just under 30 % (or a little under one third).  The other white blood cells (monocytes, eosinophils and basophils) make up the rest. In total it should add up to 100 %.

Why did I say the blood test values were for a white woman? What difference does it make? Well, men tend to be larger than women (on average, again there are always exceptions) so men tend to have more blood and therefore more blood cells than women. Children have less blood and again, the numbers for a child will be different to those of an adult.

What difference does race make? On average (again there are exceptions) West Indian or African people (or descendents of these peoples) tend to have a different normal range for white cell counts, absolute neutrophil counts and platelet counts.

I am a white female, if I had a platelet count of 124 that would be considered lower than normal, however if I was a women of African descent that would be perfectly normal. These are biological differences, measured in many thousands of people. What is important is that the doctors treating you, know what is normal for you.

One of the best summaries of “Typical normal values for Blood Test Results” can be found in the leukaemia booklets that you can download from the Leukaemia Research Fund website. The results are usually found in a table right at the back.  Here is a link to a booklet called Leukaemia and Related Diseases. The table is on page 83, (the second last page of the book). You will need Adobe Acrobat Reader to open the file or you can ask the LRF to send you a hard copy by post. Please note, these booklets are written for people in the UK who are receiving treatment from the NHS.

So What does this mean?

What is normal?  Well normally about slightly more than half (~60%) of your white blood cells should be neutrophils. The remaining third (~30%) of your white cells should be lymphocytes. The remainder is made up of monocytes, eoisnophils and basophils.

If you don’t have as many neutrophils as you should have you have “neutropenia” or you are “neutropenic”. This can be caused by some types of chemotherapy drugs and is also seen in some types of leukaemia. Neutropaenia is sometimes treated by giving G-CSF which stands for granulocyte-colony stimulating factor. If you are having chemo your doctors may delay or reduce a dose to allow your neutrophil levels to recover on their own. The Leukaemia Research Fund also produce a booklet called “Dietary advice for patients with neutropenia“

If you are having chemo, your doctors will have an idea of what blood levels are normal for you. Your neutrophil levels usually increase, without treatment when you stop chemo.

You can download a pdf of this article here – blood-count pdf

The clipart images are taken from SmartDraw 2008 and Understanding Cancer Ltd. The data is from Understanding Cancer Ltd and Mosby’s Manual of Diagnostic and Laboratroy Tests (3rd Edition) by Pagana and Pagana.

The Leukaemia Research Fund websites is http://www.lrf.org.uk

If you like what you’ve read here, you can now buy a print copy of my book from

http://www.lulu.com/content/paperback-book/understanding-cancer-2008-2009/7216905