By Dr Ananya Mandal, MD
Hypoglycemia or low blood sugar refers to when blood levels of glucose drop to a below normal level.
Insulin deficiency is one of the main causes of diabetes. When food enters the bloodstream, insulin moves glucose out of blood and into cells where it is used as a source of energy. In type 1 diabetes, the cells responsible for producing insulin are damaged and no insulin is produced, leading to a rise in blood sugar levels. In type 2 diabetes, the blood sugar levels remain high because the amount of insulin produced is inadequate.
On the other hand, people with diabetes may also have an impaired glucagon response to blood sugar levels that have become low, meaning that the usual signal to the liver to break down glycogen and provide glucose is not made. People who take insulin or other antidiabetic medications to lower their blood sugar may therefore lack the ability to normalize their blood sugar once it has become low, putting them at an increased risk of severe hypoglycemia and coma.
Causes of hypoglycemia
The causes of hypoglyaemia in diabetic patients include:
Hypoglycemia most commonly occurs as a side effect of antidiabetic medications. Insulin use is the most common cause of hypoglycemia which is particularly likely to occur if an overdose of insulin has been taken or if the drug is administered without food intake.
Examples of oral medications that work by increasing insulin production include chlorpropamide, glimepiride, glipizide and glyburide. Other oral drugs that may cause a fall in blood sugar include repaglinide, nateglinide and sitagliptin. A combination of these diabetes medications may also cause hypoglycemia. However, some antidiabetic treatments such as metformin, acarbose, pioglitazone and miglitol do not cause hypoglycemia.
The timing of meals and eating is very important among people taking insulin and other blood sugar lowering medications. The amount of insulin taken needs to be balanced with the amount of food eaten if a normal or near-normal level of blood glucose is to be maintained. Hypoglycemia is likely if insulin is not taken as advised and if there is little or no carbohydrate intake. Most commonly, it occurs due to delayed or missed meals or snacks.
The risk of hypoglycemia is raised in individuals who have drunk excess amounts of alcohol, especially without food.
Vigorous exercise, especially without adequate food intake, depletes the glycogen levels and there may be a severe fall in blood sugar.
Reviewed by Sally Robertson, BSc
Last Updated: Oct 25, 2013