Blood test results explained
Reference ranges, flagged results and what your numbers actually mean — a plain-English guide to reading the private blood test report we send you, and knowing when to follow up with your GP.
When your blood test results land in your inbox, they arrive as a table of markers, each with your value and a reference range printed beside it. To anyone outside a laboratory that can look like a wall of numbers and abbreviations. This guide explains how to read it, what a flagged result really means, and why your report is best understood alongside a clinician rather than in isolation.
Important: This guide explains how blood test reports are laid out and what the terms mean. It is not a substitute for a diagnosis. Always read your own results with the reference ranges printed on your report, and discuss anything concerning with your GP or a qualified clinician.
What is a reference range?
A reference range is the set of values a laboratory would expect to see in healthy people, worked out from large groups of test results. It is printed beside every marker on your report, usually in the same units as your result. If your value falls inside that range, it is considered within normal limits for that laboratory; if it falls outside, it is flagged high or low.
Set per laboratory
Each accredited laboratory derives its own ranges from its methods and population, so the same marker can differ slightly between reports.
Always on your report
Read your value against the range printed next to it, never against a range you found online — the units and method may not match.
A band, not a pass/fail
A result just outside the range is often harmless. Context, symptoms and trends matter more than any single number.
What a flagged result means
A flag — usually marked H (high) or L (low), or shown in colour — simply means your value sits outside the reference range. It does not, by itself, mean you are ill. Many things move a result out of range without being a health problem:
- Recent food or drink — glucose and lipids shift markedly after eating, which is why some tests require fasting.
- Hydration and time of day — kidney markers and cortisol vary with fluid intake and the body's natural daily rhythm.
- Exercise and supplements — a hard workout can raise muscle enzymes; vitamin and iron supplements skew their own markers.
- A minor illness — a recent cold can temporarily lift white blood cells or inflammatory markers.
What matters is the size of the deviation and the pattern across related markers. A slightly low value in an otherwise normal report is usually reassuring; a large deviation, or several markers in the same system out of range together, is worth a conversation with a clinician.
Common blood test panels explained
Most reports group markers into panels. Here is what the main ones look at, in plain terms. Treat these as orientation only — your report carries the exact markers and ranges that apply to you.
| Panel | Typical markers | What it tells you |
|---|---|---|
| Full blood count (FBC) | Haemoglobin, white blood cells, platelets, haematocrit | A snapshot of your blood cells. Low haemoglobin points to anaemia; raised white cells can suggest infection or inflammation; platelets show how well your blood clots. |
| Lipid profile (cholesterol) | Total cholesterol, HDL, LDL, triglycerides, non-HDL | Your fats in the blood. High LDL and triglycerides raise cardiovascular risk; higher HDL is generally protective. Results are read together, not in isolation. |
| Thyroid function | TSH, free T4, free T3 | How your thyroid is working. A high TSH with low free T4 suggests an underactive thyroid; a low TSH can point to an overactive thyroid. Symptoms matter as much as numbers. |
| Liver function (LFTs) | ALT, AST, ALP, bilirubin, albumin, GGT | How your liver is coping. Raised ALT and AST can signal liver cell stress; bilirubin relates to bile flow; albumin reflects longer-term liver function. |
| Kidney function | Creatinine, eGFR, urea, electrolytes | How well your kidneys filter. eGFR is the headline number — a persistent low value is worth discussing with your GP. Urea and creatinine rise with dehydration or reduced kidney function. |
| HbA1c (diabetes) | HbA1c | Your average blood sugar over the last 8–12 weeks. 42–47 mmol/mol is 'pre-diabetes' range; 48 mmol/mol and above may indicate diabetes. A single result is not a diagnosis on its own. |
| Vitamin D | 25-hydroxy vitamin D | Bone, immune and energy health. Below 25 nmol/L is generally considered deficient; many people in the UK run low over winter. Supplementation is common but should follow a result, not a guess. |
Why clinician-reviewed results matter
A blood test report is most useful when someone qualified has looked at the whole picture — not just whether each number is in range, but how the markers relate to one another and to how you actually feel. At Cheshire Bloods Clinic every sample is taken by an experienced phlebotomist and analysed by a UKAS-accredited laboratory, and your results come back with the reference ranges and a plain-English explanation so you can act on them.
Samples you can trust
Taken by experienced phlebotomists at our Widnes and Crewe clinics, then processed by the same accredited pathology laboratories used by NHS and private hospitals.
Results you can read
Your report arrives by secure email with reference ranges alongside each marker and a plain-English explanation. If anything needs urgent attention, we call you.
When to follow up with your GP
Book a GP appointment, or speak to a clinician, if any of these apply:
- • A marker is flagged well outside the reference range, not just slightly.
- • Several related markers in the same panel are out of range together.
- • A result matches symptoms you have been experiencing (fatigue, weight change, pain).
- • A marker that was previously normal has changed noticeably.
- • Your report advises follow-up, or you simply feel unwell.
If you are unsure what your results mean for you, call us on 0330 088 4438 (Phone lines 11am–7pm weekdays, 10am–6pm weekends) and we will talk you through it, or take your report to your GP who can interpret it with your full history.
Frequently asked questions
Analysed by our UKAS accredited laboratory partners
Every sample we draw at our Widnes and Crewe clinics is processed by established UK laboratories working to UKAS accredited standards, so your results are as reliable as those from any hospital pathology service.
