Glycated haemoglobin (HbA1c)
Glycation of proteins is the weighted mean proportional to the mean glucose concentration over the lifespan of the red blood cell.
Diagnosis and monitoring of treatment of diabetes mellitus.
20-41 mmol/mol haemoglobin
HbA1c is accepted for the diagnosis of type 2 diabetes in the UK, but should not be used to diagnose type 1 diabetes or in the following contexts; childhood, pregnancy, renal failure, haemoglobinopathy trait, anaemia, HIV, abnormal red cell turnover, or any recent drug treatment likely to affect glycaemia or red-cell turnover.
Type 2 diabetes diagnosis WHO: ≥48 mmol/mol with second indicator (either symptomatic or laboratory).
Type 2 diabetes mellitus NICE CG66 treatment target 48-59 mmol/mol.
Type 1 DM: NICE CG15 treatment target HbA1c ≤59 mmol/mol without frequent disabling hypoglycaemia; consider ≤48 mmol/mol where there is high arterial risk.
Our laboratory was an early adopter of IFCC traceable HbA1c measurement and its use in the diagnosis of diabetes (see our 2011 Lancet article entitled “HbA1c; an old friend in new clothes”). We have also published our experience of the impact of the presence of haemoglobin variants on HbA1c interpretation. Our laboratory uses ion exchange chromatography to assess IFCC-traceable HbA1c; the detection of any of the >1,000 variant haemoglobins which may affect result interpretation is reported back to the test requestor.
For more information on difficult cases, contact Dr Shivani Misra or Sophie Barnes.
Record last updated
August 20, 2025
Sample Container
4ml EDTA Vacutainers (Lavender top)
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Test Results
Yes, we have a Pathology User Guide
Yes. Please email your request to Imperial.nwlpcustomerservice@nhs.net
Results are communicated to clinical staff and are normally not communicated direct to patients either on telephone requests or in written report. If you need to contact us please click here to view the contact details page
Please contact the Customer Service Team Monday to Friday from 8:30am – 6:00pm on 0203 313 5353. Alternatively, see the Pathology User Guide for how to contact the relevant department. If advice is not urgent you can also email your query to Imperial.nwlpcustomerservice@nhs.net
Additional tests may be added by discussion with the relevant laboratory. The time limit for adding additional tests to a sample already received in the laboratory will depend on the type of sample and the department it was sent to.
Information on the repertoire of tests performed by pathology, including reference ranges, turnaround times and specimen requirements, can be found in the test directory.
Different tests have different sample stability requirements. If a comment on results indicates that the sample was delayed, the links below will indicate which tests may have been affected. This information is for serum or plasma samples.
For some tests, the impact of delay is consistent and these are marked with an arrow:
↑ indicates tests where delayed centrifugation results in falsely elevated results and the true level is likely lower than that reported.
↓ indicates tests where delayed centrifugation results in falsely lowered results and the true level is likely higher than that reported.
If there is no arrow, the true level may be lower or higher than reported.
Please interpret results with caution and consider the impact of any uncertainty.
The comment on the report will state how delayed the sample was. Please click the relevant link below to see which other tests may have been affected.
| >8h | >12h | >24h | >48h | >72h |
Phlebotomy services are not managed by NWLP. For further information please see:
Imperial College Healthcare Trust Phlebotomy services
Chelsea and Westminster Hospital NHS Foundation Trust Phlebotomy services
NWLP operates UKAS accredited medical laboratories as per the references below. The current scope of accreditation for all NWLP’s laboratories can be found on the UKAS website.
UKAS accredited medical laboratory/medical diagnostic service:
- Clinical Biochemistry No. 8673
- Haematology and Blood Transfusion No. 8674
- Infection & Immunity Sciences (Including Immunology, Virology, Microbiology and Histocompatibility and Immunogenetics ) No. 8659
- Cellular Pathology (Including Histopathology, Cytology and Molecular Pathology) No. 9615
If you require copies of our certificate of accreditation and associated documentation please contact Imperial.nwlpcustomerservice@nhs.net.
UKAS requires the laboratories to be accredited for a particular repertoire/scope (ISO15189), any changes or additions to repertoire require assessment by UKAS (extension to scope).
The BD Hospital Tube Guide, BD GP Tube Guide and BD Paediatric Tube Guide provide visual references to the correct tube types and collection instructions.
Home testing
INSTRUCTION SHEET FOR BLOOD SAMPLE COLLECTION
We also have two instruction videos available (one with subtitles and one without) – please click on the links to view the videos on Google.
Our accreditations
Upholding excellence in diagnostic standards
Our laboratories are accredited by the UK Accreditation Service (UKAS) against the international standard ISO15189:2022. UKAS is the accreditation body for the UK that assesses medical laboratories.
Find out more about our accreditations on the UKAS website.
UKAS website