High neutrophils: what it means and what to do

High neutrophils usually mean your body is reacting to something. A bacterial infection is often behind it, but a hard workout, strong stress or smoking can be enough. It is rare for a blood disorder to be the cause.

What high neutrophils mean

Neutrophils are your first defence against bacteria. When needed, your body sends more into the blood: from a reserve stuck to the walls of your blood vessels and from your bone marrow.

That is why they rise quickly, even for harmless reasons. When the absolute count is above your report’s limit, it is called neutrophilia.

The number alone does not say why: how you feel and your other results matter.

What causes high neutrophils

The last one is rare.

• A bacterial infection: The most common cause: for example in the throat, the lungs or the urinary tract. There is often a fever too.
• Exercise and stress: A hard workout or strong stress raises them for a few hours. They then come down by themselves.
• Smoking: People who smoke often have more neutrophils. After quitting, they usually come down within a year.
• Inflammation: For example arthritis, an inflammatory bowel disease, or recent surgery or an injury.
• Cortisone and other medicines: Cortisone raises them, sometimes a lot, even without an infection. Do not stop it on your own: tell your doctor.
• Pregnancy: They rise a little in pregnancy. That is normal.
• Blood disorders: They are rare. Usually other blood count values change too, such as platelets or haemoglobin.

Symptoms

High neutrophils cause no symptoms on their own. If there are any, they come from the cause.

With an infection there may be a fever, shivers, a sore throat, a cough or a burning feeling when you pass urine. If you feel well, exercise, stress or smoking are often behind it.

High neutrophils and low lymphocytes

The two often turn up together. Stress, hard exercise, cortisone or a bacterial infection can raise neutrophils and lower lymphocytes.

With percentages it is also partly the maths: when one share grows, the others shrink. That is why the absolute counts are what you look at.

The ratio between the two, neutrophils divided by lymphocytes, rises with inflammation. But it has not been shown to tell you more than CRP.

Which tests to read alongside them

These tests help show where it comes from.

What to do if they are high

The cause matters, not the number. Where to start:

• Think about the days before the test: an infection, a hard workout or strong stress often explain the result.
• Show the report to your doctor, who decides whether and when to repeat the test. It is usually repeated once any infection has passed.
• If you take cortisone or other medicines, tell your doctor. Do not stop them on your own.
• If you smoke, quitting brings them down, usually within a year.
• Before your next blood test, avoid hard exercise the day before.

When to worry

Talk to your doctor if:

• They stay high on a second test, with no clear reason.
• Other blood count values are out of range too, such as platelets or red cells.
• You have had a fever for days, sweat at night or are losing weight without trying.
• You have a fever with strong shivers: see a doctor the same day.
• You have a fever and feel confused, breathless or faint: call 112 or go to the emergency department.

Frequently asked questions

High neutrophils: should I worry? Usually not, if you feel well and the rest of your blood count is normal. Exercise, stress, smoking or an infection you just had are often behind it. Show the report to your doctor anyway.

Do high neutrophils mean an infection? Not necessarily. They are the blood cells that react most to exercise and stress: a hard workout the day before is enough to raise them.

Can high neutrophils mean a blood disorder? Rarely. In that case other blood count values usually change too, and the neutrophils stay high over time. If there is no clear reason, your doctor can ask for more tests.

Does cortisone raise neutrophils? Yes, often by a lot, even without an infection. If you take it, tell your doctor before reading the result, and do not stop it on your own.

High neutrophils in pregnancy: is it normal? Yes, they rise a little in pregnancy. If you have a fever, see a doctor the same day; for other questions, ask your obstetrician.

How long do they take to come down? After exercise or stress, usually within a day. After an infection, usually from a few days to a few weeks once you recover. If you smoke, they usually come down within a year of quitting.

Sources

• Fioredda and colleagues, European guidelines on the diagnosis and management of neutropenia in adults and children. HemaSphere, 2023. PMID 37008163
• Newburger and Dale, evaluation and management of patients with isolated neutropenia. Seminars in Hematology, 2013. PMID 23953336
• Merz and colleagues, absolute neutrophil count by Duffy status among healthy Black and African American adults. Blood Advances, 2023. PMID 35994632
• Andersohn and colleagues, systematic review of agranulocytosis caused by non-chemotherapy drugs. Annals of Internal Medicine, 2007. PMID 17470834
• Higuchi and colleagues, current smoking is a reversible cause of a raised white cell count. Preventive Medicine Reports, 2016. PMID 27583199