What are the causes and symptoms of nocturnal hypoglycemia (low blood sugar at night)?

From the Guidelines

Nocturnal hypoglycemia should be managed by monitoring blood glucose before bedtime, aiming for levels above 140 mg/dL (7.8 mmol/L), and consuming a small bedtime snack containing 15-20 grams of complex carbohydrates and protein if levels are lower, as recommended by the American Diabetes Association 1. To prevent and manage nocturnal hypoglycemia, patients with diabetes should:

• Monitor their blood glucose before bedtime and aim for levels above 140 mg/dL (7.8 mmol/L) before sleep
• Consume a small bedtime snack containing 15-20 grams of complex carbohydrates and protein if levels are lower, such as a small apple with peanut butter, a slice of whole grain toast with cheese, or a small bowl of high-fiber cereal with milk
• Consider adjusting the timing or dosage of evening insulin, particularly long-acting insulins like glargine or detemir, in consultation with their healthcare provider
• Use continuous glucose monitoring systems to detect nighttime lows, as symptoms like sweating, trembling, and confusion often go unnoticed during sleep
• Be aware of risk factors, including excessive exercise before bedtime, alcohol consumption, and skipping evening meals
• Educate family members about emergency glucagon administration for severe episodes, as severe hypoglycemia can progress to loss of consciousness, seizure, coma, or death 1. It is essential to note that nocturnal hypoglycemia is particularly dangerous because the body's counter-regulatory hormone response may be blunted during sleep, and prolonged hypoglycemia can lead to severe consequences, including seizures, loss of consciousness, or rarely, death 1.

From the Research

Definition and Prevalence of Nocturnal Hypoglycemia

• Nocturnal hypoglycemia is a common acute complication of people with diabetes on insulin therapy, particularly in those with type 1 diabetes 2, 3, 4.
• It is estimated that over half of all episodes of severe hypoglycemia occur during sleep, and nocturnal hypoglycemia is often asymptomatic and unrecognised 3.
• The precise incidence of nocturnal hypoglycemia is difficult to determine, but continuous glucose monitoring has shown that it occurs frequently in people taking insulin 3, 4.

Causes and Consequences of Nocturnal Hypoglycemia

• The inability to control glucose levels during sleep, the impact of external factors such as exercise or alcohol, and the influence of hormones are the main causes of nocturnal hypoglycemia 4.
• Nocturnal hypoglycemia can have several negative somatic, psychological, and social effects for people with diabetes, including seizures, coma, and cardiovascular events 2, 3, 4.
• Recurrent exposure to nocturnal hypoglycemia may impair cognitive function and lead to the development of acquired hypoglycemia syndromes, such as impaired awareness of hypoglycemia 2, 3.

Prevention and Treatment Strategies

• Various strategies can be used to minimize the risk of nocturnal hypoglycemic episodes, including regular blood glucose monitoring, ingestion of appropriate bedtime snacks, and the use of short- and long-acting insulin analogues 2, 5.
• Continuous glucose monitoring (CGM) can reduce the number of nocturnal hypoglycemia episodes with the help of alarms, trend arrows, and evaluation routines 4.
• Automatic glucose adjustment (AID) systems, in combination with CGM and an insulin pump, have their particular strength in nocturnal glucose regulation and the prevention of nocturnal hypoglycemia 4.
• Long-acting insulin analogs, such as insulin detemir or insulin glargine, may be the best option to provide basal insulin coverage in patients who do not choose or require continuous subcutaneous insulin infusion, and are associated with a lower risk for nocturnal hypoglycemia than traditional human basal insulin 5.