Insulin is synthesized from its precursors, preproinsulin and proinsulin in the beta cells of the islets of Langerhans and serves as a regulator for the storage and production of carbohydrates. Secretion of insulin is stimulated by an increased glucose concentration in circulation. This leads to higher insulin concentrations and more rapid tissue assimilation of glucose followed by a decline in insulin concentrations as the glucose concentration reduces. The relationship between glucose and insulin must be strictly balanced. When this balance is disturbed, insulin is either under- or over-excreted. Insulin concentrations are severely reduced in insulin-dependent diabetes mellitus (IDDM) and hypopituitarism. Insulin concentrations are raised in non-insulin dependent diabetes mellitus (NIDDM), obesity, insulinoma and certain endocrine conditions such as Cushing syndrome and acromegaly.
Clinical details: 
The predominant clinical indications for insulin measurement include: a) the diagnosis of insulinoma and other causes of hypoglycaemia, b) the diagnosis and study of cases of insulin resistance, c) the differentiation between insulin-and non-insulin-dependent diabetes, d) characterisation and follow-up of states of glucose intolerance, e) the determination of beta-cell reserve during glucose tolerance test or after a carbohydrate rich meal, as a guide for initiating insulin therapy.
Reference range: 

See Chemistry Reference Ranges Document at Automated Chemistry Laboratory at Guy's and St Thomas'

Sample type and Volume required: 
Serum. Even slightly haemolysed samples are unsuitable for analysis.
Call in advance: 
Turnaround time: 
7 days
Patient instructions: 


Storage and transport: 
Send frozen on dry ice
Blood Sciences Department-Guy's And St Thomas' Hospital
St Thomas' Hospital
North Wing - 5th Floor
Westminster Bridge Road
London SE1 7EH
Contact: 020 7188 9247

Guy's Hospital
Southwark Wing - 4th Floor
Great Maze Pond
London SE1 9RT
Contact: 020 7188 4781
Automated Chemistry Laboratory at Guy's and St Thomas' Clinical Advisory Service
Monday – Friday, 09:00-17:00 h: 07738897061
Out of hours, weekends & bank holidays: find details on Rotawatch on Trust intranet GTi, or contact via GSTT switchboard.
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 26/11/2021