. 2021 Feb 7;64(5):963–970. doi: 10.1007/s00125-020-05366-3

Table 1.

Levels of hypoglycaemia that should be reported in clinical trials, and which have clinical implications for people with diabetes

Level	Name	Plasma glucose	Implications
1	Hypoglycaemia alert	<3.9 mmol/l^a	Lower limit of ‘glucose in range’ Usually asymptomatic Treat to prevent hypoglycaemia Consider regimen change if recurrent
2	Clinically important	<3 mmol/l	Associated with impaired cognitive function Repeated episodes cause reduced awareness Predicts severe hypoglycaemia Associated with cardiac arrhythmias Predicts mortality
3	Severe	Not specified	Cognitive decline results in the need for treatment by another person May be further divided to specify episodes requiring parenteral therapy and/or episodes associated with loss of consciousness or seizure

Level

Name

Plasma glucose

Implications

Hypoglycaemia alert

<3.9 mmol/l^a

Lower limit of ‘glucose in range’

Usually asymptomatic

Treat to prevent hypoglycaemia

Consider regimen change if recurrent

Clinically important

<3 mmol/l

Associated with impaired cognitive function

Repeated episodes cause reduced awareness

Predicts severe hypoglycaemia

Associated with cardiac arrhythmias

Predicts mortality

Severe

Not specified

Cognitive decline results in the need for treatment by another person

May be further divided to specify episodes requiring parenteral therapy and/or episodes associated with loss of consciousness or seizure

Data from The International Hypoglycaemia Study Group [2]

^aIn the original document, the International Hypoglycemia Study Group (IHSG) had defined level 1 as glucose ≤3.9 mmol/l [2] but this was refined by a subsequent consensus to make a clear distinction between this classification and the lower limit of the desirable glucose range, which is 3.9 mmol/l [3]