Hypoglycemia occurs when levels of insulin and glucose (blood sugar) are out of balance. It occurs most often in patients who use insulin. All patients with type 1 diabetes, some people with type 2 diabetes and maturity-onset diabetes of the young (MODY), many people with latent autoimmune diabetes of adulthood (LADA) and most women with gestational diabetes use insulin.

Many factors can alter glucose levels in people with diabetes. Common triggers of low blood glucose in people with diabetes include:

• Taking too much insulin or other diabetes drugs (antidiabetic agents). Insulin and antidiabetic agents are used to decrease the amount of glucose circulating in the blood. Taking too much of these medications can bring glucose levels lower than they should be.
  
  
• Exercising excessively. Exercise lowers glucose levels by encouraging the transfer of glucose from the blood to the cells, where it is used for energy. Too much physical activity in comparison to the amount of food eaten, or medications taken, can result in hypoglycemia.
  
  
• Eating too little food. Food provides the body with glucose and raises blood glucose levels. Eating insufficient food in comparison to the dose of insulin or antidiabetic agents taken can result in hypoglycemia.
  
  
• Delaying or skipping a meal or snack. Delaying or skipping a scheduled meal while still taking the scheduled dose of insulin or antidiabetic agents can cause hypoglycemia.
  
  
• Eating too few carbohydrates. The majority of glucose in the blood after a meal comes from the carbohydrates in food. Not ingesting enough carbohydrates can result in glucose levels that are too low.
  
  
• Drinking alcohol, especially on an empty stomach. Normally, the liver changes stored carbohydrates (glycogen) into glucose when blood glucose levels begin to drop. It then releases the glucose into the blood to prevent or delay a low blood glucose reaction. However, when alcohol is in the body, the liver concentrates on clearing the alcohol from the blood instead of creating glucose.
  
  
• Improperly handling a glucose meter. Recent research suggests that many patients using manually coded glucose meters often do so incorrectly and may experience insulin dosing errors and glycemic problems.
  
  
• Taking non-diabetes medication. Some medications can lower glucose levels, including:
  
  
• Aspirin or other salicylates
• Acetaminophen (painkiller)
• Sulfonamides (used to treat infections)
• Quinine (used to treat malaria)
• Pentamidine (used to treat pneumonia)
• Haloperidol (used to treat nervous, mental and emotional conditions)
• Anabolic steroids

Other medications, such as heart and blood pressure medications (antihypertensives, such as beta blockers) can cause hypoglycemia unawareness, a condition in which the normal symptoms of low blood glucose are not felt or noticed.

Other triggers of low glucose can include:

• Certain other endocrine disorders, including hypothyroidism, adrenal insufficiency or hypopituitarism (underactive pituitary gland)
  
  
• Insulinoma (a rare tumor of the pancreas that results in the secretion of an excess amount of insulin).
  
  
• Other sources of hyperinsulinemia.
  
  
• Rare tumors that consume excess glucose.
  
  
• Liver disease.
  
  
• Prenatal conditions. When the glucose level of a pregnant woman with diabetes is persistently high, the fetus’ pancreas produces extra insulin. As a result, the baby may have hypoglycemia at birth.
  
  
• Ketotic hypoglycemia. 
  
  
• An inherited metabolic disorder called SCADD (short-chain acyl-coenzyme A dehydrogenase deficiency)

Sometimes the cause of low glucose in people who do not have diabetes is unknown (idiopathic).