Granulocytes: what neutrophils, eosinophils and basophils do

On your result it sits as one line among the rest: granulocytes, 4.8 ×10⁹/L. Three smaller lines sit underneath it. Granulocytes are white blood cells and in most people they make up roughly 55 to 70 percent of the total. Neutrophils, eosinophils and basophils are all three granulocytes.

That last point is what most pages leave out. They treat the three separately, as if they were three different subjects.

What strikes me when I explain results: people only grasp their white blood count once they see the family. Family first, then the members.

What are granulocytes?

Granulocytes are white blood cells with grains in their cell fluid. Those grains, the granules, give the group its name. They hold enzymes and signalling substances that the cell releases during an infection or an allergic reaction. There are three types: neutrophils, eosinophils and basophils.

The names come from the laboratory. Under the microscope the granules of eosinophils take up the red dye eosin, and those of basophils the blue-purple basic dye.

Neutrophils stain strongly with neither, hence "neutral".

All three belong to your innate immunity, the part that reacts immediately and builds no memory (PMID 20176265). They appear together on the leukocyte differential, the breakdown of your white blood cells.

Here is a comparison that sticks: think of granulocytes as the in-house emergency team of a large building. Neutrophils are the big general crew that heads out first at every alarm. Eosinophils are the specialised team for parasites and allergic inflammation.

Basophils are the smallest team and mostly ring the bell.

Where that comparison breaks down matters just as much. No central control room directs these cells, because they respond to chemical signals around them. And a bigger crew does not mean you are better protected.

What is the difference between granulocytes and lymphocytes?

Granulocytes belong to your innate immunity. They react within minutes to hours, to almost any intruder, without distinction. Lymphocytes belong to your adaptive immunity: they recognise a specific pathogen and remember it (PMID 20176265). Granulocytes are the fast generalists, lymphocytes the slower specialists with memory.

On your result they sit side by side. In adults neutrophils are usually the largest group and lymphocytes the second.

That ratio shifts with all sorts of things. A bacterial infection pushes neutrophils up, while many viral infections push lymphocytes up instead.

What a low lymphocyte count does and does not say sits in our article on low lymphocytes. How both systems work together is covered in how your immune system works.

Where are granulocytes found?

They are made in your bone marrow and most of them stay there. Your marrow keeps a sizeable reserve of mature neutrophils on standby. Of what does circulate, a share sticks to the vessel walls. So a tube of blood measures only a fraction of the total.

That explains something people often find confusing. Your neutrophil count can climb sharply within an hour without your body making a single new cell.

Exercise, acute stress, smoking and prednisone loosen cells from the vessel wall. Those cells then land in the measurable pool.

Give blood right after a hard training session and you measure something different from a quiet morning.

As soon as granulocytes are needed, they leave your bloodstream. They squeeze between the cells of your vessel wall towards the tissue where the alarm went off. Pus consists largely of spent neutrophils.

The three granulocyte types side by side

Neutrophils are by far the largest group, eosinophils a few percent and basophils almost nothing. Each of the three rises or falls in different situations. The numbers below are indicative. Every laboratory applies its own reference ranges, and the range printed on your own result is the range that counts.

Basophils are so rare that a result of 0.0 percent is entirely ordinary. For eosinophils the upper limit usually sits around 0.5 ×10⁹/L. What can sit behind a value above that is covered in high eosinophils.

Why the absolute count outweighs the percentage

A differential appears twice: as a percentage of your white blood cells and as an absolute count per litre. That absolute count is the number doctors read. A percentage can rise purely because another cell type falls, without a single extra neutrophil being added.

Take two people, both with 45 percent neutrophils. In the first, leukocytes sit at 9.0 ×10⁹/L, so the absolute count works out at 4.1 ×10⁹/L: perfectly normal.

In the second, leukocytes sit at 2.8 ×10⁹/L. That same percentage then comes down to 1.3 ×10⁹/L, which falls below most lower limits.

Same percentage, different conclusion.

If the absolute count is missing from your result, you can work it out yourself: the percentage divided by 100, times your total leukocytes.

Low neutrophils: when is that a concern?

A mildly lowered neutrophil count is often temporary and harmless. Doctors look mainly at how low. Roughly speaking, below about 1.5 ×10⁹/L is called mild, below 1.0 moderate and below 0.5 ×10⁹/L severe. Infection risk can rise mainly in that last group. Here too, every lab sets its own limits.

The usual suspects are a recent viral infection, certain medications, an autoimmune condition, or a shortage of vitamin B12 or folate. Thuisarts, the patient site run by Dutch GPs, describes how a GP looks at abnormal blood values.

And then there is an explanation almost no Dutch page mentions.

A substantial share of people of African or Afro-Caribbean ancestry carry the Duffy-null phenotype, a variant in the ACKR1 gene. People with this variant have structurally lower neutrophil counts in their blood, without a higher risk of infection (PMID 35994632).

Since 2024 it has had a name of its own: Duffy null-associated neutrophil count. The literature describes it explicitly as a non-pathologic phenotype, so not as a disorder (PMID 39259539).

The friction sits in the reference range. In the Netherlands it is largely based on a predominantly white population. Someone with this phenotype can therefore show up as "neutropenic" on the result while nothing need be wrong.

Back to the comparison: a smaller crew is not a weaker crew here.

This is no reason to wave a low value away. It is a reason to mention your ancestry and your earlier results when you discuss that value. Years of low counts without infections is a different story from one low count with a fever.

What a low value means for you is something you settle with your GP. How this blood value is measured is explained under neutrophils.

High neutrophils: what can be going on?

Above roughly 7.5 ×10⁹/L labs usually speak of neutrophilia. The everyday causes come first: a bacterial infection, inflammation, heavy exercise, smoking, pregnancy, stress and prednisone. In most people the value settles again on its own.

In our experience it is mostly timing effects. A sample taken the morning after a marathon gives a different number from a sample on a quiet day.

If the value stays high across several measurements, without an infection and without a clear explanation, that belongs with your GP.

If your main issue is feeling run down often, the answer usually does not sit in this one number. When frequent colds do and do not point at your immune system is covered in that article.

What is the absolute basophil count?

"Absolute" here means the number of cells per litre of blood, not the percentage. For basophils that number sits below roughly 0.1 ×10⁹/L in most people. It is the smallest group of white blood cells you have. A result of 0.0 ×10⁹/L is therefore not an alarm signal.

Precisely because the number is so small, the percentage is extra unreliable here. The difference between 0.4 and 0.9 percent can come down to a handful of cells on the count.

Basophils release histamine, the same substance behind itching, sneezing and a runny nose. They are involved in allergic reactions and in chronic hives.

The smallest team with the loudest bell, to stay with the comparison.

A mildly raised basophil count usually says little on its own. A clearly and persistently raised value is one a doctor would rather read alongside the rest of your blood count. The separate blood value basophils shows what that measurement looks like.

What do you do with your result?

Never read your granulocytes in isolation. One abnormal number in a differential says little. The ratio between the cell types and the trend over time say far more. A second measurement a few weeks later, with no infection in between, is often more informative than the first.

My advice stays the same with every result: look at the pattern, not the one number printed in red. It saves a lot of needless worry.

To see the whole white blood count in context, the leukocyte differential is included in the extended health checkup.

Concretely: copy down your absolute counts rather than the percentages, note which medications you take and whether you were ill that week, and put your earlier results next to them. Take that list to your GP and ask whether a repeat measurement makes sense for you.

References

1. Chaplin DD. Overview of the immune response. J Allergy Clin Immunol. 2010;125(2 Suppl 2):S3-S23. PMID 20176265.
2. Merz LE, et al. Absolute neutrophil count by Duffy status among healthy Black and African American adults. Blood Adv. 2023;7(3):317-320. PMID 35994632.
3. Hibbs SP, et al. Cancer Trial Eligibility and Therapy Modifications for Individuals With Duffy Null-Associated Neutrophil Count. JAMA Netw Open. 2024. PMID 39259539.
4. Thuisarts. Patient information on blood testing and abnormal blood values. Available via thuisarts.nl.

Every blood test result at Vitalcheck includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.