HbA1c

Test Alias / Common Abbreviations

 

Glycated haemoglobin

 

Department

 

Biochemistry
Royal Stoke University Hospital, Leighton Hospital, Macclesfield District General Hospital 


Pre-analytical information

 

Add-on requests: accepted up to 7 days post sampling - however due to limited retention time of haematology samples it may only be possible to add on within 1-2 days of receipt.

Minimum Retest Interval: 55 days – unless retesting for diagnosis and previous result ≥48 mmol/mol

Sample Collection Instructions:
Collect the blood sample using normal venepuncture technique into an EDTA tube (purple-top). 

Sample Transport & Stability Information:
Samples should be sent to the laboratory on the same day as collection to ensure sample integrity is maintained.  If a delay in receipt of the sample is anticipated, please contact the laboratory to discuss storage requirements.

Stable in whole blood for 1 day at room temperature and 14 days at 4-8oC.

For generic information on test requesting, sample labelling and packaging, and sample transport – see the frequently asked questions here.

 

Sample Type, Container & Volume

 

Adult sample type:

 

 

 

 

 

 

 

 

 

 

 

 

Turnaround Time

Based on receipt at testing site.
Within 72 hours

 

 

 

 

20-41 mmol/mol
Non-diabetic

42-47 mmol/mol
Impaired glucose regulation. High-risk of diabetes. Provide intensive lifestyle advice and repeat annually.

≥48 mmol/mol
Indicative of diabetes. If asymptomatic repeat HbA1c using the same method – a second result ≥48 mmol/mol confirms diagnosis. If second result is <48 mmol/mol treat as high-risk and repeat in 6 months or sooner if symptoms develop.

Results outside the reference range do not necessarily indicate disease. Similarly, results within the reference range do not preclude abnormality. Please contact the Duty Biochemist for discussion of individual patient results.

HbA1c reflects average blood glucose over the lifespan of the red blood cell, typically 2-3 months. It is used to monitor glycaemic control in patients with known diabetes and for diagnosis of type 2 diabetes. 

In some clinical scenarios HbA1c measurement is unreliable and cannot be used as a diagnostic test. This can be due to altered red cell survival or direct analytical interference with HbA1c measurement. Please see here for more information and details of conditions that preclude reliable HbA1c.

There are a number of non-pathological factors that can influence levels of specific analytes, giving falsely elevated or reduced levels. If you require more information regarding the effects of these factors on the individual test results, please contact the Duty Biochemist.

For more information, please see click here.

Reviewed / Updated On: 19/11/2025