Reading your report
How to Read Blood Test Results
To read a blood test report, start with the test name, result, units and reference range, then check any flags, comments and report status. This guide explains those parts with a fictional example; it does not interpret your individual results.
Medipher explains medical wording in plain English — it does not diagnose or replace a clinician. If this is a medical emergency, call your local emergency number immediately.
The short answer
The short answer
Start with the test name and result, then read the units and reference range printed on that same report. Check any flags, laboratory comments and report status. Layouts vary, so use the wording and key on your own report.
A flag such as H, L, high, low or abnormal simply means your value sits outside that laboratory's band. It is an automatic comparison made by the laboratory system, not a diagnosis.
A result outside the range does not by itself establish a diagnosis, and a result inside the range does not rule out every health problem. Interpretation depends on the test, your symptoms, your history and your other results.
The parts of a typical report
Laboratories present results in slightly different layouts, but the same pieces of information are almost always there, and reading them in the order below keeps the page manageable: test name, result, units, reference range, flags, then clinical context.
The report itself goes by several names. In the UK it is usually called a blood test result; elsewhere, and on many patient portals, you may see the same document described as laboratory results, lab results or blood work. Test names differ too — a full blood count (FBC) in the UK is a complete blood count (CBC) in the United States and several other countries. The layout and the way you read it are the same.
- Test or marker name
- What was measured — often abbreviated, such as Hb for haemoglobin or MCV for mean cell volume. The same substance can be named differently by different laboratories.
- Result
- The measured value. On its own it means very little: it has to be read next to the units and the range printed beside it.
- Units
- The scale used, for example g/L or 10⁹/L. Comparing a value with a range or an older result in different units will give you a misleading picture.
- Reference range
- The band of values the laboratory expects for most people tested in the same way. Ranges differ between laboratories and can differ by age, sex and pregnancy, which is why your own report prints its own.
- Flags
- Markers such as H, L, high, low or abnormal, added automatically when a value falls outside the range. They highlight where to look, not what it means.
- Laboratory comment
- A short note from the laboratory, such as a suggestion to repeat the test or a remark about the sample quality. Comments are directed at the requesting clinician.
- Report status
- Whether the report is preliminary, final or amended. Codes vary between laboratories, so check what your own report says rather than assuming a universal meaning.
A worked example
The extract below is fictional. It is included to show the layout of a report — the columns, the flags, the comment and the status line — not as a set of values to compare yourself with. Tap or click an underlined part of the report to see a short explanation of what it is.
Example report — fictional results for educational purposes
All values and reference ranges are illustrative only. They are not universal medical reference ranges and should not be compared with your own results.
Tap an underlined part to see what it means
| Haemoglobin (Hb) | 112 | g/L | 120–150 | |
|---|---|---|---|---|
| White cell count (WBC) | 6.8 | 10⁹/L | 4.0–11.0 | — |
| Platelets | 265 | 10⁹/L | 150–400 | — |
| MCV | 76 | fL | 80–100 | |
| RDW | 16.2 | % | 11.5–14.5 |
Test name
Identifies what was measured. Names are often abbreviated (Hb, MCV) and can differ slightly between laboratories. Select a test name in the table to open its glossary entry.
Reading that example
In the fictional report above, three values sit outside the printed range: haemoglobin and MCV are flagged low, and RDW is flagged high. Read individually they say very little. Read together, they describe a pattern that a clinician would recognise as worth investigating — which is exactly what the laboratory comment suggests.
This is the central idea in reading any report: patterns across several results, seen alongside your symptoms and history, carry far more meaning than any single flagged value.
Looking at your own results? Medipher can explain the terminology in plain English. Explore what this result means.
What a reference range can and cannot tell you
A reference range is usually built from measurements taken in a large group of people considered healthy, covering the middle portion of their results. By design, a small proportion of healthy people fall outside it. That is why a value just outside the range is common and often unremarkable.
Equally, a value inside the range is not a clean bill of health. Your usual level may sit near one end of the range, so a shift within it can still be meaningful to a clinician who can see your previous results.
- Ranges are laboratory-specific — do not compare your value with a range from a different report or website.
- Ranges can differ by age, sex and pregnancy.
- Trends over time are often more informative than any single measurement.
- Some tests have no simple range, and are reported as detected, not detected or equivocal instead.
An important limit
A result outside the reference range does not by itself establish a diagnosis, and a result within range does not rule out every health problem. Only a clinician who knows your situation can interpret your results.
Flags and wording, line by line
Flags are added by the laboratory system, which compares your value with the reference range printed on that same report. They tell you where a value sits relative to a band — never what caused it and never what it means for you.
- H or High
- The value is above the upper end of that laboratory's reference range for the test.
- L or Low
- The value is below the lower end of that range.
- Abnormal
- A general marker used by some systems for any value outside the range, or for a word-based result that is not the expected one.
- In range
- The value sits within the printed band. It is reassuring in context, but it does not rule out every health problem.
- Out of range
- The value sits outside the printed band. Reference ranges are built so that a small proportion of healthy people fall outside them.
- Not detected
- The substance or organism was not found at the level the test can measure.
- Equivocal
- The result sits in a borderline zone where the test cannot give a clear answer; a repeat is usually suggested.
- Laboratory comment
- A short note from the laboratory, often suggesting a further test or remarking on sample quality. It is written for the requesting clinician.
A flag is not a diagnosis
Flags are automated comparisons against one laboratory's reference range. They highlight where a clinician should look; they do not establish or exclude any condition.
Word-based results
Not every test produces a number. Microbiology, virology and some specialist tests report words instead, and those words have precise meanings.
- Not isolated — used in microbiology when a particular organism did not grow in culture.
- Below the limit of detection or below the limit of quantitation — the test can tell something is very low but cannot measure it precisely.
- Preliminary, final or amended — the status of the report itself rather than of any single result.
This guide covers the layout of the page rather than the biology behind each line. See what common blood-test values such as haemoglobin, WBC, platelets and TSH mean in the wider blood test results guide.
Sensible next steps
- Look at your own report's ranges and units rather than ones you find elsewhere.
- Note the questions a result raises for you, and take them to your appointment.
- Ask whether a flagged value needs repeating, and when.
- Seek medical help now, rather than waiting for an explanation, if you are unwell or your symptoms are worsening.
Common questions
What does the reference range on my report mean?
It is the band of values that laboratory expects for most people tested in the same way. It is produced by that laboratory, so it may differ from the range printed on another report.
Is a result outside the range always a problem?
No. Reference ranges are built so that a small proportion of healthy people fall outside them. A value slightly outside the range is common and is interpreted alongside your symptoms, history and other results.
What do the letters H and L mean next to my result?
They are flags meaning higher or lower than the laboratory's reference range for that test. They are generated automatically and highlight where to look rather than what it means.
Why do the units matter?
The same substance can be reported on different scales — for example g/L or g/dL. Comparing a value with a range or an older result in different units gives a misleading impression.
What does 'final' mean on a report?
It usually indicates the laboratory has completed and authorised the report, as opposed to a preliminary or amended one. Status wording and codes vary between laboratories, so check your own report or ask the requesting service.
Related medical terms
Plain-English definitions of the wording you may see on your own report.
Medipher uses publicly available information and guidance from trusted health organisations in the UK and internationally, where relevant. They are educational and do not replace advice from your own healthcare professional.
- 01NHSBlood tests — Health A to Z
- 02Association for Laboratory MedicineLab Tests Online UK — Tests index
- 03NHSGP services
- 04MedlinePlus (US National Library of Medicine) — United StatesHow to understand your lab results
Understand your own report
If a line on your report still does not make sense, Medipher can turn the wording into a clear, plain-English explanation. It is educational support to help you prepare for a conversation with your clinician — it does not diagnose or review your health.
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