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What is hypoglycaemia

Overview of hypoglycaemia
in diabetes

In diabetes, hypoglycaemia generally arises as a consequence of pharmacologic treatment that causes blood glucose levels to drop below the normal range. While mild hypoglycaemia usually resolves with prompt ingestion of carbohydrates, more significantly reduced glucose levels can impair cognitive function, lead to loss of consciousness, and even threaten life. The link between hypoglycaemia and increased mortality has been documented in several studies.1

Nocturnal hypoglycaemia poses a particular challenge because the sleeping patient is not in a position to intervene and many episodes are asymptomatic. Repeated exposure to nocturnal hypoglycaemia can blunt counterregulatory mechanisms, with potentially serious clinical consequences.2

Intensive glucose-lowering therapy may not achieve its purpose – avoidance of mortality and morbidity from diabetes complications – unless hypoglycaemia risk can be managed. Strategies to minimize hypoglycaemia can help patients safely achieve glycaemic control and thus prevent or delay complications.


Hypoglycaemia definitions have varied across time, place, and setting. In order to harmonize terminology in clinical trials and encourage an appropriate response to hypoglycaemia in clinical practice, the IHSG has developed the following definitions:

These definitions partly align with the American Diabetes Association/Endocrine Society (ADA/ENDO) hypoglycaemia classification system.3 An important difference is that ADA/ENDO classifies blood glucose < 3.9 mmol/L without symptoms as “asymptomatic hypoglycaemia.” The IHSG takes the position that “alert value” more accurately reflects this presentation and avoids over-identifying hypoglycaemia.

The above IHSG definitions do not apply to young children, who are generally not able or expected to self-treat. The International Society for Paediatric and Adolescent Diabetes (ISPAD) characterizes severe paediatric hypoglycaemia as follows: “The child is having altered mental status and cannot assist in their care, is semiconscious or unconscious, or in coma.”4


In type 1 diabetes (T1D), for which insulin treatment is assumed, the prevalence of severe hypoglycaemia increases with the duration of the disorder. As shown in the graph below, the annual prevalence in people who have had T1D for under 5 years is about 20%, while it exceeds 40% in those who have had the disorder for over 5 years.

In type 2 diabetes (T2D), both duration and medical treatment influence the risk. The annual risk of severe hypoglycaemia is significant for T2D patients on sulfonylureas (SUs) and on insulin, especially if on insulin for over 5 years (> 20% risk).

Non-severe hypoglycaemia, which adults can self-treat, is more common than severe hypoglycaemia, but poses far less risk to health and life.

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Adapted from Diabetologia 2007;50:1140.


  1. Glucose concentrations of less than 3.0 mmol/L (54 mg/dL) should be reported in clinical trials: a joint position statement of the American Diabetes Association and the European Association for the Study of Diabetes. Published in both Diabetes Care 2017 Jan; 40(1): 155-157 and Diabetologia 2017;6-:3-6.
  2. Cryer PE. Glycemic goals in diabetes: trade-off between glycemic control and iatrogenic hypoglycemia. Diabetes 2014;63:2188.
  3. Edelman SV, Blose JS. the impact of nocturnal hypoglycemia on clinical and cost-related issues in patients with type 1 and type 2 diabetes. Diabetes Educ 2014;40:269.
  4. Seaquist ER et al. Hypoglycemia and diabetes: a report of a workgroup of the American Diabetes Association and The Endocrine Society. Diabetes Care 2013;36:1384.
  5. ISPAD Clinical Practice Consensus Guidelines 2009 Compendium: Assessment and management of hypoglycemia in children and adolescents with diabetes. Pediatric Diabetes 2009;10(Suppl. 12):134.