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EspañolWhat a full blood test usually includes
A full blood test is not one test but a bundle of smaller ones. In UK practice it usually means a full blood count (FBC) and urea and electrolytes (U&Es), often with liver function tests, a cholesterol test and a blood sugar test, and sometimes thyroid or iron tests. Nobody defines the phrase officially, so two people who ask for “a full blood test” can come home with eight lines or forty.
So the first thing to check on your own results is which groups were actually requested. The table below covers the great majority of routine requests from a GP surgery. Each group has its own page here, explaining what it measures and in what order its lines are meant to be read.
| Test group | Lines | What it is looking at |
|---|---|---|
| Full blood count (FBC) | 10–20 | Red cells, haemoglobin, white cells and their types, platelets |
| Urea and electrolytes (U&Es) | 4–6 | Urea, sodium, potassium, creatinine, with an eGFR calculated from creatinine |
| Liver function tests (LFTs) | 5–7 | ALT, ALP, bilirubin, albumin, sometimes AST and GGT |
| Lipid profile | 4–6 | Total cholesterol, HDL, non-HDL, triglycerides, sometimes LDL |
| HbA1c or glucose | 1 | Average blood sugar over recent months, or blood sugar on the day |
| Thyroid function tests (TFTs) | 1–3 | TSH, and free T4 or free T3 when needed |
| Iron studies | 1–4 | Ferritin, sometimes serum iron and transferrin saturation |
What can show up on a full blood test
Read group by group, a full blood test answers a handful of broad questions about how your body is running at the moment. It can show that you are anaemic and hint at which kind, that your blood sugar sits in a range worth discussing, that your kidneys or liver are under some strain, or that your cholesterol raises your risk of heart disease over the next ten years.
Each of those is a starting point rather than a verdict. Type 2 diabetes, for instance, is not settled by one result: NICE asks for a second blood test when a first one comes back in the diabetes range in someone without symptoms.
- Blood countAnaemia is defined by the WHO as haemoglobin below 130 g/L in men and below 120 g/L in non-pregnant women. The size of the red cells gives a first clue to the cause, alongside white cells and platelets.
- Blood sugarAn HbA1c of 42 to 47 mmol/mol, or a fasting glucose of 5.5 to 6.9 mmol/L, signals a high risk of type 2 diabetes. From 48 mmol/mol or 7.0 mmol/L, a second test is needed to confirm diabetes.
- Kidneys and liverCreatinine and eGFR describe how well the kidneys filter. ALT and alkaline phosphatase describe strain on the liver and the bile ducts.
- Long-term heart riskA total cholesterol above 9.0 mmol/L or a non-HDL cholesterol above 7.5 mmol/L calls for a specialist assessment under NICE guidance, even without a family history.
Is there a blood test that checks everything?
No. A routine set of tests is not a cancer screen. Even the tumour markers built around cancer are not reliable on their own: Cancer Research UK points out that some are found in conditions that are not cancer, and that some cancers make no marker at all. A normal FBC and normal U&Es say nothing either way about most cancers.
A full blood test also leaves out whatever was not requested. Vitamin D, B12, folate, hormones and most infections are separate tests. And the cholesterol lines measure substances carried in your blood, not the state of your arteries.
Finally, it describes one morning. A single set of results is a photograph, not a film: most of what a GP reads in it comes from comparing it with your earlier results, or with the reason you were sent for the test.
Read it in groups, not top to bottom
The useful order is not the order printed on the page. Start with the reason for the test: if it was tiredness, the blood count and the iron studies carry the answer, and a slightly odd sodium is probably background. Then read each group as a unit: haemoglobin with MCV and ferritin, ALT with ALP, creatinine with eGFR.
Only then look at the flagged lines, and ask how far outside they are rather than whether they are outside. A ferritin of 28 against a lower limit of 30 and a ferritin of 4 can carry the same L. Layouts differ between laboratories, but the reading order does not: test, value, unit, range, then the flag, which may be a letter, an asterisk, bold type, an arrow or nothing at all.
Expect a flag or two even if you are well. Each range is set so that about 1 in 20 healthy people fall outside it. Spread across twenty lines, that adds up: a perfectly healthy person is more likely than not to see at least one flag.
Last, compare with your previous results if you have them. Many GP surgeries share results through the NHS App, which makes the comparison easier. A value that has drifted steadily within its range over three years can say more than a single flagged result.
How to prepare for a full blood test
Preparation depends on the boxes ticked on your form, not on the word “full”. A full blood count needs no preparation at all. A fasting glucose does, and your surgery will tell you how long to go without food. Cholesterol mostly does not: NICE does not require a fasting sample for a full lipid profile, and European specialist societies have recommended non-fasting lipid testing as the routine since 2016.
One instruction surprises people: NICE advises adults not to eat any meat in the 12 hours before a blood test used to estimate kidney function (eGFR). Plain water is fine unless you were told otherwise.
The draw itself matters too. European sampling guidance asks that the tourniquet come off as soon as blood flows and that you avoid pumping your fist, both of which can disturb some results.
Can I ask my GP for a full blood test?
You can ask, but on the NHS a blood test is requested for a reason: a symptom, a condition being followed, a medicine that needs monitoring. If a GP, nurse or specialist thinks you need one, they will tell you how to book it, usually at the surgery or a hospital clinic, and the tests are chosen to answer that question rather than to cover everything.
If you are aged 40 to 74 and have no existing heart, kidney or diabetes condition, you should be invited to an NHS Health Check every five years. It includes a cholesterol test and possibly a blood sugar test, and gives you a score for your risk of heart disease, stroke, type 2 diabetes or kidney disease over the next ten years.
Outside the NHS, private clinics and pharmacies sell bundles without a GP referral. As one example, a London private clinic listed a “biochemistry profile” covering a full blood count, kidney and liver tests, glucose, cholesterol and triglycerides at £77 on 7 October 2026, on top of a GP consultation from £89. Prices vary widely between providers.
Does a general check-up actually help?
This is one place where the evidence is unusually clear, and it runs against intuition. A Cochrane systematic review pooled 17 randomised trials and 251,891 participants to ask whether offering general health checks to adults reduces illness or death. It found little or no effect on deaths from any cause or from cancer, with high-certainty evidence, and probably none on deaths from heart disease. Its conclusion: general health checks are unlikely to be beneficial.
What they do produce is diagnoses. In one of the trials, people offered health checks collected 20% more new diagnoses over six years than those who were not. A label arrived; the outcome did not change.
Read the scope of that finding carefully, because it is narrow and it matters. It concerns screening adults who have no symptoms, across several organ systems at once. It says nothing about a test your GP requested for a reason, nothing about following a condition you already have, and nothing about investigating a symptom. Those are not check-ups; they are questions with an answer attached, and they remain worth doing.
Questions to bring to your GP
Bring the results themselves, not a summary or a screenshot of one number. Units and ranges differ between laboratories: a UK haemoglobin of 135 g/L is the same as 13.5 g/dL on a result printed abroad.
If you have heard nothing a few weeks after your test, contact your GP surgery: some surgeries only get in touch when a result needs discussing. And some findings should not wait for a routine appointment. A value far outside its range, several lines of the same group moving together, or a flagged result that matches how you feel, such as fever, unusual bruising or growing breathlessness, is a reason to call the surgery rather than wait.
- Why these tests?The reason for the request tells you which group carries the answer and which flags are background.
- How far outside?Ask whether a flagged value is just over the line or well beyond it, and whether that distance changes anything.
- Has it moved?Ask to compare with earlier results, ideally from the same laboratory, so that a change of method is not mistaken for a change in you.
- What happens next?A repeat, another test, or nothing at all: each is a legitimate answer, and knowing which one saves weeks of wondering.