Full blood count (FBC / CBC)
White blood cell count blood test: what a high or low result means
What your white blood cell count (WBC) measures, what high or low white cells can mean, and what to ask your doctor.
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Explain my results → Available on web, iOS & Android.What is white blood cell count?
White blood cells are part of your immune system. They help your body fight infections and respond to injury and inflammation. The white blood cell count, shown as WBC or WCC, is the total number of white cells in a sample of your blood and is part of a full blood count (FBC, or CBC in the US). Your report may also break the total down into the different types, such as neutrophils and lymphocytes, called a differential.
Why is this test done?
- To look for signs of infection or inflammation
- As part of a routine full blood count
- To monitor treatments that can affect the immune system or bone marrow, such as chemotherapy or some long-term medicines
- To investigate symptoms such as fevers, frequent infections or unexplained bruising
What does a high white blood cell count mean?
A high white cell count is called leucocytosis (leukocytosis in the US). Most often it is the body responding normally to something, rather than a problem with the blood itself.
Possible reasons include:
- Infection, especially bacterial infection
- Inflammation, for example from arthritis or inflammatory bowel disease
- Physical or emotional stress, recent surgery or injury
- Smoking
- Some medicines, such as steroids
- Less commonly, a blood or bone marrow condition such as leukaemia
What does a low white blood cell count mean?
A low white cell count is called leucopenia (leukopenia in the US). A slightly low result is common and is often harmless, but a low count can make it harder to fight infections.
Possible reasons include:
- Viral infections, which can lower the count for a short time
- Some medicines, including chemotherapy and certain antibiotics or antithyroid drugs
- Autoimmune conditions, such as lupus
- Low vitamin B12 or folate
- Naturally lower counts in some people, including many people of Black African or Middle Eastern heritage
- Less commonly, a bone marrow condition
Why we don't list a "normal range". Reference ranges differ between laboratories and can depend on your age, sex and whether you are pregnant. The range printed next to your result on your own report is the one that applies to you, so use that, and talk to your doctor about what your result means for you.
What can affect your white blood cell count result?
- A recent infection or vaccination
- Exercise, stress or pregnancy, which can raise the count
- Medicines, especially steroids, which raise it, and chemotherapy, which lowers it
- Time of day, as counts vary slightly over 24 hours
Make sense of the whole report, not just one line
Results are easier to understand together. Patiently AI explains your report as a whole and writes personalised questions for your next appointment.
Try it with your own results → Paste, upload or photograph your results.Questions to ask your doctor
- Which type of white cell is high or low?
- Could a recent infection or one of my medicines explain this?
- Do I need a repeat test, and when?
- Is there anything I should do to protect myself from infection?
Frequently asked questions
Does a high white blood cell count mean I have an infection?
Not necessarily. Infection is a common cause, but stress, smoking, steroids and inflammation can all raise the count. Your doctor will look at which type of white cell is raised and at your symptoms.
Should I worry about a slightly low white cell count?
A count just below the range is common and often harmless, particularly after a viral illness or in people whose counts are naturally lower. Your doctor may simply repeat the test to see whether it returns to the range.
What is a differential?
A differential breaks your total white cell count down into the five main types: neutrophils, lymphocytes, monocytes, eosinophils and basophils. Each type does a different job, so the pattern helps explain the cause of a high or low total.
Can Patiently AI explain my white blood cell count result?
Yes. Paste your results, or upload a photo, PDF or Word file, and Patiently AI explains them in plain English, sticking to the numbers and ranges on your own report rather than adding its own, and suggests questions to ask your doctor. It is free, needs no account, and removes identifying details on your device first.