We’d all like to sleep soundly without the fear of having low blood glucose levels (BGLs) overnight. The technical jargon for this event is a nocturnal hypoglycaemic episode.

The definition of a nocturnal hypoglycaemia (hypo) is when your BGLs drop to below 4mmol/L (or the minimum level set by your healthcare team) overnight. Of all hypoglycaemic events, almost 50% occur at night, during sleep.

The people at risk of experiencing hypoglycaemia are those living with diabetes who are prescribed insulin or sulfonylurea medications. For those who do experience hypos there are some risk factors which may be managed.

Possible risk factors for low overnight BGLs

• Eating too few carbohydrates in general or at the evening meal
• Skipping the evening meal altogether
• Taking too much quick acting (mealtime) insulin for the carbohydrate in the evening meal, this may be due to inaccurate carb counting or a miscalculation
• Too high a level of nighttime basal (background) insulin
• Intermittent fasting (periods of not eating) and not adequately altering medication doses
• Drinking alcohol
• Doing more physical activity than normal – this may be planned exercise, or other activities you don’t think of including shopping, housework, or dancing
• Exercising in the afternoon or evening
• Experiencing a hypo in the past 24 hours
• Puberty, menopause, or other life stage changes
• Elevated altitude.

Signs that you have experienced a nocturnal hypo

Some people experience no signs or symptoms at all when they have encountered a BGL below 4mmol/L. This is known as hypo-unawareness. These people are more likely to sleep through the event.

The risk of hypo-unawareness is increased if you have been living with type 1 diabetes for longer than 10 years or have a history of hypo events. For others there may be a range of evidence, internal and external:

• Waking, especially suddenly with a start or with anxiety from an unknown cause
• Sleep disturbance, dreaming or nightmares
• Unexplained fatigue
• Waking with hot, clammy skin, or experiencing damp bedclothes especially around the neck area
• Higher than usual fasting BGLs on waking; this may be a rebound effect from the overnight hypo
• Sudden rapid or slow breathing rate
• A racing or very slow pulse rate
• Shaking or trembling
• Disorientation or confusion
• Nausea and generally feeling unwell
• Unexplained changes in mood such as irritability or extreme impatience.

Most people will experience one or more of these symptoms. In extreme cases, the consequences of a hypo event are seizure, cardiac arrhythmias (disturbed heart function), coma or even death.

Prevention

Prevention is always better than cure. Consulting with your healthcare team is the best place to start. Together you can work on a strategy for prevention of nocturnal hypoglycaemia.

Some suggestions may include:

• Adjusting treatment such as the type, timing, or dosage of insulin and/or other medications
• Regulating the timing and carbohydrate content of meals
• Learning or refreshing your skills in areas such as carbohydrate counting
• Attending education programs such as OzDAFNE – Dose Adjustment For Normal Eating
• Checking BGLs before going to bed (discuss with your healthcare team to determine a glucose level to be above before going to sleep), during the night and first thing in the morning to understand how your BGLs fluctuate over the sleep period
• Using continuous glucose monitoring (CGM) with a low glucose alarm set, with or without a closed loop insulin delivery system
• Knowing the signs/symptoms of nocturnal hypo
• If necessary, having a carb containing snack for before bedtime
• Combining alcohol consumption (within healthy guidelines) with carbohydrate-containing food
• Requesting your healthcare team perform a full review of medications, diet, and lifestyle
• Having hypo treatment within reach.

For a full description of how to treat an acute hypoglycaemic event, follow this link.

If you believe you may be experiencing or are at risk of nocturnal hypoglycaemia, make an appointment to speak to your GP or endocrinologist who, with your healthcare team, will ensure you have a plan that is specifically tailored for you.

And with this peace of mind, a good night sleep awaits.

By Constance Russell Registered Nurse, Credentialled Diabetes Educator