Key Takeaways
- Blood test results are compared against a reference range — values outside the range are flagged but may not indicate illness.
- Common abbreviations include FBC, U&Es, LFTs, TFTs, CRP, HbA1c, and eGFR.
- Reference ranges can vary between laboratories, so always use the range printed on your report.
- If results are abnormal, your GP will interpret them in context before deciding on next steps.
How Blood Test Reports Are Structured
Whether you receive your results through the NHS App, a GP letter, or a private provider portal, the format is broadly the same. Each test result includes:
- Test name — the analyte being measured (e.g. haemoglobin, TSH, creatinine).
- Your result — a numerical value with units (e.g. 135 g/L, 2.5 mIU/L).
- Reference range — the range considered normal for your age and sex (e.g. 120–150 g/L).
- Flag — results outside the reference range are usually marked as "H" (high), "L" (low), or highlighted in colour.
Results are grouped by test panel. For example, a "full blood count" section will list all the individual measurements (haemoglobin, white cells, platelets, MCV, etc.) together.
Common Abbreviations Explained
| Abbreviation | Full Name | What It Measures |
|---|---|---|
| FBC | Full blood count | Red cells, white cells, platelets, haemoglobin |
| Hb | Haemoglobin | Oxygen-carrying protein in red cells |
| WBC | White blood cell count | Immune cells |
| PLT | Platelets | Blood clotting cells |
| MCV | Mean cell volume | Average red cell size |
| U&Es | Urea and electrolytes | Kidney function |
| eGFR | Estimated glomerular filtration rate | How well kidneys filter blood |
| LFTs | Liver function tests | Liver enzymes and proteins |
| ALT | Alanine aminotransferase | Liver enzyme (most specific) |
| TFTs | Thyroid function tests | Thyroid hormone levels |
| TSH | Thyroid-stimulating hormone | Pituitary signal to thyroid |
| CRP | C-reactive protein | General inflammation marker |
| ESR | Erythrocyte sedimentation rate | Inflammation (slower to change) |
| HbA1c | Glycated haemoglobin | Average blood sugar over 2–3 months |
| PSA | Prostate-specific antigen | Prostate health marker |
What Do the Reference Ranges Mean?
Reference ranges (also called normal ranges) represent the values found in 95% of healthy people of the same age and sex. This means that 5% of completely healthy people will have a result outside the range simply by chance. A slightly out-of-range result is not an automatic cause for concern.
Reference ranges can differ between laboratories because of variations in equipment, reagents, and calibration methods. Always compare your result to the reference range printed on your specific report, not to ranges you find online.
Common Results and What They Might Mean
Low Haemoglobin
The most common cause of low haemoglobin (anaemia) is iron deficiency, especially in women of reproductive age. Other causes include vitamin B12 deficiency, chronic disease, and blood loss. Your GP will usually order iron studies and a reticulocyte count to determine the cause.
High Cholesterol
Total cholesterol above 5.0 mmol/L is considered elevated in the UK. However, the total number alone does not tell the full story — the ratio of total cholesterol to HDL is more important. A ratio below 4.0 is ideal. Treatment decisions also consider your overall cardiovascular risk (age, blood pressure, smoking status, family history).
Elevated Liver Enzymes
Mildly elevated ALT or GGT is very common and often caused by fatty liver (non-alcoholic fatty liver disease), alcohol consumption, or medications such as statins. A single mildly abnormal result is often repeated in 4 to 6 weeks before further investigation.
Abnormal Thyroid Results
A high TSH with low T4 suggests hypothyroidism (underactive thyroid). A low TSH with high T4 suggests hyperthyroidism (overactive thyroid). Subclinical cases (where TSH is mildly abnormal but T4 is normal) are common and may not require treatment immediately but should be monitored.
When to Worry
Most out-of-range results are mild and explainable. However, you should contact your GP promptly if:
- Your result is significantly outside the range (not just marginally).
- You have symptoms that correlate with the abnormal finding.
- Multiple results from different panels are abnormal at the same time.
- Your GP or the private provider has flagged results as requiring urgent follow-up.
If you are using a private testing service, always share your results with your GP, especially if anything is abnormal. They can provide clinical context and arrange further investigation through the NHS if needed.
Tips for Tracking Your Results Over Time
- Keep a copy of every blood test report — trends over time are more informative than any single result.
- Use the NHS App to access your GP test results digitally.
- Note the conditions under which each test was taken (fasting, time of day, medications, illness).
- If you use different laboratories, be aware that reference ranges may differ — comparing absolute values across labs can be misleading.
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