What is an FBC?
Learn what a full blood count blood test measures, and why you may need one.
A Full Blood Count (FBC) is a commonly requested blood test in the UK. Known as a complete blood count (CBC) in the US, this test checks the makeup of your blood and is used to assess your overall health, detect infections, and identify conditions such as anaemia.
In this article we cover:
- What does a full blood count test measure?
- What can a FBC blood test show?
- Would an FBC detect cancer?
- What is a normal FBC range?
- FBC blood test in pregnancy
- Why do I need a full blood count?
- How do you get an FBC blood test?
- What do I do if my FBC results are abnormal?
What does a full blood count test measure?
An FBC is often used as a first-line test to give a broad overview of your general health. It focuses on the three main components of your blood.
These are:
- Red blood cells
- White blood cells
- Platelets
Each of these have different roles in the body, and their differing levels can give clues as to how your body is functioning.
Red blood cells
Red blood cells are the most common type of blood cell. They contain haemoglobin which delivers oxygen around your body to the tissues and organs that need it.
An FBC will measure the number of red blood cells in your blood, the amount of haemoglobin you have, as well as measurements such as the size and concentration of red blood cells.
An FBC also measures additional red blood cell markers such as mean cell volume (MCV) and mean cell haemoglobin (MCH), which help doctors understand the size and haemoglobin content of your red blood cells. Typically, haemoglobin levels are used to indicate if you are anaemic.
White blood cells
Your white blood cells are part of your immune system. They help fight infections and protect your body from germs and bacteria. There are a few different types of white blood cell.
A full blood count will measure how many white blood cells you have, as well as your levels of different white blood cells such as neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
Platelets
Platelets help your blood to clot properly and are an important part of healing. An FBC detects your levels of platelets and the average size of them.
What can an FBC blood test show?
It’s important to remember an FBC can’t give a diagnosis. But it can help determine if you need further tests or clinical reviews.
A full blood count blood test can:
- Identify imbalances in blood cell levels
- Suggest whether you have had a recent infection
- Help identify anaemia (for example iron, or B vitamin deficiency)
- Cardiovascular conditions
- Act as a starting point for further investigation
Does a full blood count test show cancer?
You might be wondering if a full blood count blood test can detect cancer. A full blood count blood test cannot diagnose cancer. However, certain cancers — particularly blood cancers such as leukaemia — may cause abnormal FBC results. If significant abnormalities are detected, further investigation may be recommended.
If you had an unusual FBC result, don’t panic. Many non-serious conditions can show up in an FBC. We cover what to do if you receive an abnormal result below. If you’re ever worried about your FBC results, you can talk to your doctor or GP.
What is a normal FBC range?
A normal FBC range depends on a few different factors such as age, sex, ethnic backgrounds, as well as the reference ranges used by individual labs, but a general range is given below [1,2].
Normal full blood count range for women:
| Type of cell | Levels in a healthy woman |
| Haemoglobin | 115-165 g/L |
| White blood cells | 4.0-11.0 x 109/L |
| Nuetrophils | 2.0-7.5 x 109/L |
| Lymphocytes | 1.5-4.5 x 109/L |
| Platelets | 150-400 x 109/L |
Normal full blood count range for men:
| Type of cell | Levels in a healthy man |
| Haemoglobin | 130-180 g/L |
| White blood cells | 4.0-11.0 x 109/L |
| Nuetrophils | 2.0-7.5 x 109/L |
| Lymphocytes | 1.5-4.5 x 109/L |
| Platelets | 150-400 x 109/L |
Please remember that values outside of these reference ranges do not always mean something is wrong, but it may be a prompt for further investigation or lifestyle changes.
FBC blood test in pregnancy
Full blood count blood tests are often a part of routine care in pregnancy. While you may need additional FBC blood tests if there is an indication, you’ll usually have one FBC at your first antenatal appointment (at around ten weeks), and then another at 28 weeks.
Your clinicians are typically monitoring your iron levels, infection markers, and for changes of blood volume.
During pregnancy, blood volume increases significantly, which can naturally lower haemoglobin levels. Regular FBC testing helps monitor iron levels and detect anaemia early. This is a completely normal and harmless test and could protect you and your baby from deficiencies.
Why do I need a full blood count?
There are several reasons you might need or want a full blood count blood test.
These include:
- Keeping an eye on your overall health
- Investigating symptoms such as fatigue or dizziness
- Monitoring existing conditions
How can I get an FBC blood test?
You may be referred to get an FBC by your healthcare provider, or if you'd like to check your levels without visiting your GP, you can order our Full Blood Count (FBC) Blood Test online, with convenient at-home or clinic-based options.
What should I do if my FBC results are abnormal?
Abnormal results aren’t an immediate cause for concern. They may just require additional review along with your medical history and symptoms.
At Medichecks, we’ll explain your results in context of your lifestyle information and any other markers we’ve tested. Within your report, we’ll let you know your recommended next steps.
References
- MacMillan, Blood tests. [cited 6 Feb 2026].
- Blood Cancer UK | Blood cells. In: Blood Cancer UK [Internet]. [cited 10 Feb 2026].