A full blood count (FBC) is one of the most widely used blood tests in UK healthcare. It counts and measures the three main types of blood cell: red cells, which carry oxygen; white cells, which are part of the immune system; and platelets, which help blood to clot. Our partner laboratory reports each result alongside its own reference range.
How you take your test: have your blood sample taken at our Maidstone clinic, or use a home sample kit where the laboratory confirms this test is suitable. Choose clinic collection or delivery at checkout and we will confirm the arrangements with you. The price covers laboratory analysis and your laboratory report; a written interpretation or consultation with Marina is optional and priced separately.
What is measured
- Red cells: haemoglobin, red cell count, haematocrit and red cell indices (MCV, MCH, MCHC, RDW)
- White cells: total white cell count, usually with a differential count of the five main types
- Platelets: platelet count, and on some analysers mean platelet volume
Useful for
- Checking for anaemia and clues to its likely type
- A baseline picture of your blood cells, or comparison with an earlier result
- Adding information when symptoms such as tiredness are being looked into, ideally alongside your GP
Sample: venous blood (EDTA tube). Biomarkers: one panel; the exact parameters reported depend on the laboratory's analyser. Fasting: not required. Included: laboratory analysis and results report; interpretation is optional and priced separately.
Full Blood Count (FBC)
Red cells
- Haemoglobin (measured): the oxygen-carrying protein; the main value used to define anaemia.
- Red cell count (measured): the number of red cells per litre of blood.
- Haematocrit: the proportion of blood made up of red cells; derived from cell count and size on many analysers.
- MCV (measured): average red cell size; small and large cells point to different causes of anaemia.
- MCH and MCHC (calculated): the average amount and concentration of haemoglobin in red cells.
- RDW (analyser-derived): how much red cell size varies.
White cells
- Total white cell count (measured).
- Neutrophils, lymphocytes, monocytes, eosinophils, basophils (measured where a differential is reported): help explain a raised or lowered total.
Platelets
- Platelet count (measured), and mean platelet volume on some analysers.
An FBC does not measure ferritin (iron stores), vitamin B12, folate or ESR.
Blood cells are made in the bone marrow and replaced continuously. Red cell production is driven mainly by erythropoietin, a hormone the kidneys release when tissues receive too little oxygen. Making healthy red cells needs iron, vitamin B12 and folate, so shortages often show up as changes in red cell size and haemoglobin content.
White cells are a mixed population. Neutrophils respond mainly to bacterial infection and inflammation, lymphocytes to viral infection and longer-term immunity, and eosinophils to allergy and some parasites. Platelets are cell fragments that plug damaged blood vessels and start clotting.
Haematology analysers count and size many thousands of cells in a small volume of blood. Some values are measured directly and others are calculated from them. If the analyser flags an unusual pattern, the laboratory may examine a blood film under the microscope. Because one sample covers oxygen-carrying, immune and clotting cells, clinicians use the FBC to look for anaemia, investigate symptoms, check the effects of some medicines and monitor known conditions.
Reference ranges usually cover the middle 95% of results from healthy people, so a few healthy people sit just outside them. Ranges vary with age and sex and between laboratories, so compare your results with the ranges on your own report.
Haemoglobin and anaemia
The World Health Organization's 2024 guideline defines anaemia in adults aged 15 to 65 as haemoglobin below 130 g/L in men and below 120 g/L in non-pregnant women, with adjustments for smoking and high altitude. It notes that cut-offs for people over 65 have not yet been established.
Common patterns
- Small red cells (low MCV) are often seen with iron deficiency, and with inherited traits such as thalassaemia; further tests tell these apart.
- Large red cells (high MCV) can occur with vitamin B12 or folate deficiency, regular alcohol intake and some medicines.
Changes that are not caused by disease
- Smoking and dehydration can raise haemoglobin; pregnancy normally lowers it.
- Recent blood donation or transfusion alters red cell values for a while.
- Many medicines affect white cells or platelets, and heavy alcohol use can affect all three cell types.
- A recent infection or very hard exercise can temporarily change white cell counts.
Neutrophils and ancestry
Normal neutrophil counts vary between ethnic groups. Many healthy people with the Duffy-null blood group, most common in people of African ancestry, have counts below conventional lower limits. A 2023 JAMA study found a central 95% range of 1.21 to 5.39 × 10⁹/L in healthy Duffy-null adults, against about 1.92 to 7.60 × 10⁹/L for the hospital's standard range.
A single value just outside the range in someone who feels well is often simply repeated. Clearly abnormal results, or any abnormal result with symptoms, should be discussed with your GP. With your consent, we can write to your GP.
People often choose an FBC to check for anaemia, for example with heavy periods, a restricted diet, regular blood donation or past low iron, or to have a baseline for future comparison. Iron stores fall before haemoglobin does, so an FBC can be normal in early iron deficiency; if iron or B12 is your main question, our iron and vitamin B12 tests may answer it more directly. A normal FBC never outweighs symptoms that need medical assessment.
People who may find it useful
- Adults wanting a baseline, or to compare with an earlier result
- People with risk factors for anaemia, such as heavy periods, restricted diets or frequent blood donation
- Regular endurance exercisers reviewing their haemoglobin as part of a wider check
When this test is not the right route
- Urgent symptoms such as unexplained bleeding or bruising, fever while on medicines that suppress immunity, chest pain or breathlessness at rest: call NHS 111, or 999 in an emergency.
- Persistent unexplained weight loss, night sweats or fevers: see your GP.
- Prescribed FBC monitoring for a medicine or condition: keep to your NHS schedule.
Healthy people without symptoms do not need a routine FBC; choosing one is a personal decision.
Established clinical use
The FBC is a routine test in investigating symptoms at any age. In older adults, low haemoglobin is generally treated as a finding to explain rather than an expected part of ageing.
Population associations
A 2010 meta-analysis of seven community studies of 11,827 older adults found that each one percentage point higher RDW was associated with a 14% higher risk of death during follow-up. This is an association across populations. It does not show that RDW causes poorer health, there is no treatment aimed at lowering it, and it is not validated for predicting an individual's lifespan.
What we do not claim
We do not use the FBC to estimate biological age or predict life expectancy. Its value for healthy ageing lies in spotting treatable problems, such as iron, B12 or folate deficiency, and in providing a personal baseline.
- Fasting: not needed. Drink normally, as dehydration can raise haemoglobin.
- Exercise and illness: avoid unusually hard training the day before, and consider booking after you have recovered from an infection.
- Tell us about recent blood donation or transfusion, pregnancy, and all medicines and supplements, including iron, B12 or folic acid. Keep taking prescribed medicines as normal.
Choose how your sample is taken when you book. We confirm the collection option, any collection fee and the expected turnaround time before you book.
- Juvenology Clinic, Maidstone (82 King Street, Maidstone ME14 1BH): Available.
- Partner collection location, including London: Available on request. We confirm availability for your postcode before you book.
- Postal home finger-prick kit: Ask before ordering. We offer a home kit only where the laboratory confirms this test is suitable for a finger-prick sample.
Sample: Venous whole blood (EDTA tube)
Collection notes: A venous sample at the clinic is the recommended route. Blood cells begin to change after collection and NHS laboratory guidance notes that samples older than 24 hours may give inaccurate results, so a postal finger-prick kit is offered only if the laboratory confirms it is suitable for a full blood count. No fasting is needed.
The price of this test covers laboratory analysis and the laboratory's results report. The report lists each result beside the laboratory's reference range.
Beyond the blood test: optional support, priced separately
- Personalised written interpretation report: £50
- General consultation: £50
- Results consultation (results discussion and follow-up advice): £100
- Personalised programme: from £150, after we assess whether a programme suits you
Consultations are with Marina, an NMC-registered nurse. She explains what your results show and how they relate to lifestyle. No prescription service is offered with these tests.
If a result suggests you need medical follow-up, we will recommend that you see your GP and, with your consent, can provide a letter to take with you. A blood test cannot rule out every condition. If you have symptoms, speak to your GP or NHS 111, and call 999 in an emergency.
Does a full blood count check my iron levels?
Not directly. It can suggest iron deficiency through haemoglobin and red cell size, but iron stores are measured by ferritin and can run low before the FBC changes.
Can an FBC detect cancer?
Some blood disorders change the FBC, which is why doctors use it when investigating symptoms. It cannot diagnose or exclude cancer on its own, and a normal result should never delay seeing your GP about worrying symptoms.
My neutrophils are flagged low but I feel well. What does that mean?
Mildly low counts are common in healthy people with the Duffy-null blood group, and can also follow viral infections or some medicines. A clinician can advise whether repeat testing is needed.
Can I use a finger-prick kit at home?
A venous sample at the clinic is our recommended route, because blood cells start to change once collected. A postal kit is offered only where the laboratory confirms it is suitable, and we will tell you before you book.
Is interpretation included in the price?
The price covers laboratory analysis and the laboratory's report with reference ranges. You can add an optional personalised written interpretation report (£50) or book a results discussion consultation (£100).
- Full blood count (FBC). Lab Tests Online UK (Association for Laboratory Medicine). https://labtestsonline.org.uk/tests/full-blood-count
- Blood tests. NHS website. https://www.nhs.uk/tests-and-treatments/blood-tests/
- Guideline on haemoglobin cutoffs to define anaemia in individuals and populations. World Health Organization, 2024. https://www.who.int/publications-detail-redirect/9789240088542
- Merz LE, Osei MA, Story CM, et al. Development of Duffy null-specific absolute neutrophil count reference ranges. JAMA, 2023;329(23):2088-2089. https://jamanetwork.com/journals/jama/fullarticle/2806162
- Patel KV, Semba RD, Ferrucci L, et al. Red cell distribution width and mortality in older adults: a meta-analysis. Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 2010;65(3):258-265. https://doi.org/10.1093/gerona/glp163
- Full Blood Count: test information. Severn Pathology, North Bristol NHS Trust. https://www.nbt.nhs.uk/severn-pathology/requesting/test-information/full-blood-count
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