Blood test results explained: numbers, ranges and context
Make sense of the report’s labels and prepare useful questions for the professional who arranged your test.
Read the guide →← Bloods & understanding results
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HbA1c and blood glucose: what is the difference?
Understand two different ways of looking at blood sugar, without turning a home reading or laboratory number into a diagnosis.
By SHIFT Some Timber · Sources checked . General information, not an individual assessment. This guide has not been reviewed by a clinician.
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The short answer
HbA1c reflects average blood glucose over roughly the previous two to three months. A glucose measurement describes the level at the time the sample is taken. They answer different questions and are not interchangeable; the clinician arranging testing should explain which is appropriate and how the result will be followed up.
North West London Pathology NHS: HbA1c · NIDDK: the A1C test and diabetes
A longer view and a moment in time
HbA1c measures glucose attached to haemoglobin in red blood cells. It is useful for particular diabetes assessments and monitoring. A glucose test is more immediate and its interpretation depends on the situation, including whether it was fasting or taken at another time. Neither result tells the whole story about a person’s health.
North West London Pathology NHS: HbA1c · NIDDK: the A1C test and diabetes
Preparation depends on the actual test
HbA1c alone does not generally require fasting. Other tests collected at the same appointment may have preparation instructions. Follow the booking information and ask the provider if anything is unclear. Do not skip food or change diabetes medicines on the assumption that every blood sugar test has the same preparation.
Know which measurement is on the report
Keep the test name, date, units and laboratory information together. HbA1c can be reported in different units from a glucose reading, so numbers found online may not be directly comparable. Before trying to make sense of a result, confirm what was measured and why. Ask for an explanation rather than converting a number into a diagnosis yourself.
Why an individual result needs context
HbA1c is not appropriate for every diagnostic situation, and some conditions affecting blood or haemoglobin can affect interpretation. An apparently reassuring result should not end a conversation about ongoing symptoms. A clinician may choose another measurement or arrange confirmation, depending on the question being investigated.
Get a clear follow-up plan
Ask: Is this a screening, diagnostic or monitoring test? Who interprets it? When will I hear? What should I do if symptoms continue before then? If you already have diabetes, use your agreed care plan and contact your care team about concerns. An educational guide cannot set your targets or advise changes to treatment.
Sources and scope
Source checking is separate from clinical review. Linked guidance may change. Product instructions and service availability must be checked on the current product or provider page.
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