Different physiological responses occur when the declining blood glucose reaches specific concentrations. Although these glycaemic thresholds are readily reproducible in non-diabetic humans (Vea et al 1992), they are plastic and dynamic and can be modified. In non-diabetic humans the glycaemic threshold at which the secretion of most counter-regulatory hormones is triggered is around 3.8mM (arterialized blood glucose), so that counter-regulation is usually activated when blood glucose falls below the normal range. Counter-regulation therefore occurs at a higher blood glucose than that at which the symptomatic response to hypoglycaemia occurs (3.0mM) and before the onset of cognitive dysfunction (2.8 mM) (Figure 10.1). The glycaemic threshold for symptoms coincides with the classical autonomic 'reaction' to hypoglycaemia which can be identified by the sudden development of physiological changes (Frier and Fisher 1999).
In people with diabetes, glycaemic thresholds can be modified by the prevailing glycaemic state, and parti-
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