Iron and haematology . Patient guide
Full Blood Count (FBC) Blood Test
Also known as: Complete Blood Count, CBC, Full Blood Examination
What is FBC
A full blood count (FBC) measures the cells in circulating blood: red cells and haemoglobin (oxygen carrying), white cells with differential (the immune system), and platelets (clotting). It is the single most commonly requested blood test in UK practice and forms the backbone of almost every clinical work-up.
This biomarker entry is being clinically reviewed by our team. The factual content draws on UK guidance (NICE, NHS, Royal Colleges and the relevant speciality society where cited).
Reference range
Reported in mixed (see table). Final reports always carry the issuing laboratory's range, which is what your clinician will interpret against.
| Group | Range | Note |
|---|---|---|
| Haemoglobin (adult men) | 130 to 170 g/L | |
| Haemoglobin (adult women) | 120 to 150 g/L | |
| White cell count | 4.0 to 11.0 x10^9/L | |
| Neutrophils | 1.5 to 7.5 x10^9/L | lower limit varies between UK labs (1.5 to 2.0); BSH convention uses 1.5 |
| Lymphocytes | 1.0 to 4.0 x10^9/L | |
| Platelets | 150 to 400 x10^9/L | |
| MCV (red cell size) | 80 to 100 fL |
What it is
An FBC quantifies the three cell lines made in the bone marrow. Red cells are indexed by haemoglobin, haematocrit, MCV (size), MCH and MCHC (haemoglobin content per cell), and red cell distribution width (variation in cell size). White cells are reported as a total and broken into neutrophils, lymphocytes, monocytes, eosinophils and basophils, which together describe the type and chronicity of any immune activation. Platelets reflect bone marrow output of clotting cells. Modern lab analysers report all of these in under a minute from a single EDTA blood sample.
Why a clinician would order it
An FBC is ordered as part of any general health check, in the work-up of fatigue, breathlessness, pallor, bruising, recurrent infections, unexplained fever or weight loss, and is part of the standard pre-operative bloods before any planned surgery including hair transplantation. It is also one of the key screening tests in pregnancy, in the monitoring of chronic disease, and to detect early effects of medications that act on the bone marrow.
If your level is outside the range
Symptoms of low FBC
- Fatigue, breathlessness, pallor (low haemoglobin)
- Recurrent or severe infections (low white cells or low neutrophils)
- Easy bruising or prolonged bleeding (low platelets)
- Headaches and reduced exercise tolerance
What low can indicate. Iron, B12 or folate deficiency (anaemia), bone marrow suppression, recent or chronic blood loss, autoimmune destruction of cells, or the effect of certain medications. A single mildly low cell line is usually investigated with a repeat plus a reticulocyte count, ferritin and B12/folate. Pancytopenia (all three lines low) is referred to haematology.
Symptoms of high FBC
- Fever, sweats, swollen lymph nodes (raised white cells, infection)
- Headache, dizziness, visual disturbance (very high haemoglobin)
- Rarely thrombosis or abnormal bleeding (very high platelet count)
What high can indicate. Acute or chronic infection (neutrophilia or lymphocytosis), inflammation, smoking and chronic lung disease (high haemoglobin), dehydration, polycythaemia vera, or reactive thrombocytosis. A markedly raised white cell count or platelet count outside of obvious infection always needs further investigation.
Testing tips
No fasting required. Avoid heavy exercise in the hour before the draw as it can transiently shift cell counts and platelet results. If you have a current viral infection, results can be temporarily abnormal and a repeat in 4 to 6 weeks usually gives a clearer baseline.
Where you can get this tested
Full Blood Count is included in the following WMG Health panels. Same-day appointments at our Harley Street clinic, with results clinician-reviewed.
Want a specific combination of markers we do not have a panel for? Build a custom panel and our clinicians will design one for you.
Symptoms often investigated with Full Blood Count
Full Blood Count is commonly tested when patients present with the following symptoms. If any of these resonate with you, the linked guides explain what to look for and which test pathway is appropriate.
Sources
UK guidance our clinicians use when interpreting this marker.
This page is general patient information, not personal medical advice. A GMC-registered clinician will review your results and tailor any interpretation to you. See our Editorial Policy for how we write and review content.
Common questions about FBC
What is a normal FBC range?
Haemoglobin (adult men): 130 to 170 g/L. Haemoglobin (adult women): 120 to 150 g/L. White cell count: 4.0 to 11.0 x10^9/L. Neutrophils: 1.5 to 7.5 x10^9/L (lower limit varies between UK labs (1.5 to 2.0); BSH convention uses 1.5). Lymphocytes: 1.0 to 4.0 x10^9/L. Platelets: 150 to 400 x10^9/L. MCV (red cell size): 80 to 100 fL. Always interpret your own results against the laboratory range printed on your report, since assay-specific reference ranges vary.
What does a low FBC result mean?
Iron, B12 or folate deficiency (anaemia), bone marrow suppression, recent or chronic blood loss, autoimmune destruction of cells, or the effect of certain medications. A single mildly low cell line is usually investigated with a repeat plus a reticulocyte count, ferritin and B12/folate. Pancytopenia (all three lines low) is referred to haematology.
What does a high FBC result mean?
Acute or chronic infection (neutrophilia or lymphocytosis), inflammation, smoking and chronic lung disease (high haemoglobin), dehydration, polycythaemia vera, or reactive thrombocytosis. A markedly raised white cell count or platelet count outside of obvious infection always needs further investigation.
Do I need to fast or prepare for the FBC blood test?
No fasting required. Avoid heavy exercise in the hour before the draw as it can transiently shift cell counts and platelet results. If you have a current viral infection, results can be temporarily abnormal and a repeat in 4 to 6 weeks usually gives a clearer baseline.
Can I order a FBC blood test privately in London?
Yes. WMG Health offers FBC as part of bespoke panels and several pre-built panels at our 134 Harley Street clinic. Results are clinician-reviewed by a GMC-registered doctor within 4 hours for the most common assays. All panels are custom-built around your specific question; bookings via /contact/ or 020 3239 3378.