Hypoglycemia or an abnormally low blood sugar level can be a critical condition requiring emergency treatment, especially if the sugar level is rapidly falling. Glucose is a vital source of energy for bodily functions, particularly the brain, which has very limited reserves of glucose and depends on its continued availability in the body.

The effects of low blood sugar on the brain include dizziness, fainting, seizures and coma. Hypoglycemia therefore needs to be identified early and promptly treated. Diagnosis is initially based on a patient's symptoms and later confirmed with the use of blood tests before treatment is arranged.

Outline of diagnosis

A general clinical profile of the patient is obtained. The details obtained include patient's age, time since last meal, time since last dose of insulin (or other blood sugar lowering medication) last alcohol intake, history of previous hypoglycemic episodes, nutrition status, history of fasting or starvation and symptoms of other endocrine or hormonal disorders.

Diabetic patients may maintain a diary cataloguing meal times, exercise habits and medications used and this can help to identify any patterns of behaviour that are likely to trigger a hypoglycemic event.

Initial assessment also involves ascertaining whether the hypoglycemia is due to life threatening conditions such as ketoacidosis, for example.

Hospitalized patients need to be assessed carefully as their usual diet has often been altered.

Assessment must also include the patient's consciousness level as a lack of blood sugar supplied to the brain can lead to permanent, irreversible brain damage.

Blood analysis is carried out to check the blood glucose and accurately diagnose the patient. In healthy individuals, blood glucose is usually maintained in the range of 72 to 144 mg/dL (4-8 mmol/L) over a 24-hour period. A low blood sugar range is generally defined as 60 to 70 mg/dL (3.3 or 3.9 mmol/L), with symptoms usually manifesting once the level becomes as low as 2.8 to 3.0 mmol/L.

After the hypoglycemia has been corrected, further blood tests such as fasting blood sugar, post-prandial blood sugar (sugar assessed 2 hours after a meal), glycated haemoglobin (HbA1c) and the oral glucose tolerance test are performed to check for diabetes in undiagnosed individuals and to monitor the control of blood sugar levels.

Other substances in the blood that may be checked in cases of unexplained recurrent hypoglycemia include insulin, proinsulin, glucagon, cortisol, electrolytes, growth hormone, liver enzymes, ketone bodies, lactic acid, ammonia, free fatty acids, carnitine, and thyroid hormone.