Author:Itunu Adeyemi
Clinical reviewer:Itunu Adeyemi (HCPC registered Biomedical Scientist)
Review date: 22/08/2026
Blood test results explained: a practical starting point
A blood test report can contain unfamiliar abbreviations, units and reference ranges. This guide explains how to read the structure of a report and what to discuss with a healthcare professional. It cannot diagnose the cause of an abnormal result.
What a reference range means
Laboratories usually display a reference range beside each result. The range describes values expected for most people in the laboratory’s reference population using that laboratory’s method. Ranges can differ between laboratories and may vary by age, sex, pregnancy status and other factors.
A flagged result is not automatically a diagnosis. Healthy people can occasionally have a result outside a reference range, while clinically important problems can sometimes be present despite a result that is not flagged. Interpretation depends on the pattern of results and the clinical context.
Why results can change
- Whether you fasted
- The time the sample was taken
- Hydration and recent exercise
- A recent infection or inflammatory illness
- Medicines and supplements
- Menstrual-cycle or pregnancy-related changes
- Differences between laboratory methods
Always use the range printed on your own report. Avoid comparing a value directly with an unrelated online range.
A sensible way to review a report
- Confirm your details, collection date and the laboratory’s units.
- Read preparation or sample-quality notes.
- Identify results marked high, low or requiring action.
- Look at related markers together rather than one number in isolation.
- Compare previous results only when units and methods are comparable.
- Note symptoms, medicines, supplements and recent illness.
- Ask what the result means for you, whether it needs repeating and what follow-up is recommended.
Common groups of blood tests
- Full blood count: measures blood-cell components and can contribute to assessing issues such as anaemia, infection or inflammation.
- Kidney and electrolyte tests: assess markers related to kidney function and fluid or electrolyte balance.
- Liver tests: report several markers that must be interpreted as a pattern and in context.
- Thyroid tests: commonly include TSH and, where appropriate, thyroid hormones.
- Lipid tests: include cholesterol-related measures used as part of cardiovascular-risk assessment.
- Glucose-related tests: may include glucose or HbA1c, depending on the clinical question.
- Nutrient markers: may include ferritin, vitamin B12, folate or vitamin D when appropriate.
These descriptions are deliberately general and are not diagnostic rules.
When to get medical advice
Follow any action note supplied with your report. Contact a qualified healthcare professional if a result is significantly abnormal, unexpected, worsening or accompanied by persistent symptoms. Do not change prescribed medicines or start high-dose supplements solely because of a private blood test result.
Seek urgent medical help for severe or rapidly worsening symptoms. Call 999 for a life-threatening emergency. For urgent help that is not an emergency, use NHS 111 or follow current NHS guidance.
Important limitations
This guide provides general education only. It does not replace individual medical advice, examination, diagnosis or treatment. Laboratory flags and reference ranges must be interpreted alongside your clinical circumstances.
Source
Suggested internal links: Biomarker A-Z; What is TSH?; male hormone blood tests explained; female hormone blood tests explained; blood tests before and during HRT; blood-test cost guide; Build Your Own Blood Test Panel.