• Nocturnal hypoglycemia is low blood sugar that happens while you sleep.
  • Risk factors for nocturnal hypoglycemia include lower hemoglobin A1c test readings, exercise, low bedtime blood glucose, and daytime hypoglycemia.
  • Talk with your doctor if you suspect nocturnal hypoglycemia. Together, you can discuss your diabetes management plan.

Nocturnal hypoglycemia is the medical term for low blood sugar that happens while you sleep.

Healthcare professionals define low blood sugar as below 70 milligrams per deciliter (mg/dL). Severe hypoglycemia is when levels drop below 55 mg/dL.

Often, daytime hypoglycemia is managed by checking your blood sugar levels and responding to symptoms.

Nighttime hypoglycemia, on the other hand, may go unnoticed. As a result, blood sugar may drop to more severe levels. A 2017 review stated that over half of severe hypoglycemia events are nocturnal.

Several key strategies can help you treat and prevent nocturnal hypoglycemia. Knowing the causes and taking action to keep blood sugar levels from dropping are effective ways to reduce the risk.

Several factors make nocturnal hypoglycemia more likely. A 2015 study including 45 people (ages 15 to 45) with type 1 diabetes who took daily insulin identified these risk factors:

  • lower hemoglobin A1c test levels (a measure of your average blood sugar level)
  • medium- or high-intensity exercise during the day, prior to the nocturnal hypoglycemic event
  • low bedtime blood glucose level
  • daytime hypoglycemia

Other potential causes for low blood sugar that occurs during the day or at night include:

  • hot or humid weather
  • changes in personal routine or schedule
  • feeling ill
  • menstruation
  • puberty (in children with type 1 diabetes)
  • high altitude
  • too much insulin
  • too few carbohydrates
  • inaccurate insulin dose timing
  • exercise
  • alcohol consumption

As this list shows, many factors — some of which are environmental — can cause low blood sugar.

Physical symptoms often alert you to low blood sugar.

If hypoglycemia happens at night, you may experience some signs. Your partner, roommate, or family members may also notice these symptoms:

  • restless sleep
  • sweaty, hot, or clammy skin
  • rapid increase in breathing
  • sudden slowing of breathing
  • racing heart rate
  • trembling or shaking
  • nightmares or sleep disturbances

If you sleep through nocturnal hypoglycemia, you may experience these symptoms when you wake up. These are signs you had low blood sugar while asleep:

  • having a headache, confusion, or irritability upon waking
  • feeling tired the following day
  • noticing damp bedsheets and clothes (signs of sweating)
  • experiencing sleep disturbances

Some people experience hypoglycemia unawareness. They may not have the common physical symptoms of low blood sugar. These individuals are more likely to sleep through an episode of nocturnal hypoglycemia.

They’re also at greater risk for severe hypoglycemia (less than 55 mg/dL), when it may not be possible to manage symptoms without assistance.

You’re more likely to have hypoglycemia unawareness if:

  • You’ve lived with diabetes for a long period of time. The Centers for Disease Control and Prevention (CDC) defines this as 5 to 10 years or more.
  • You have recurring episodes of low blood sugar.
  • You take some medications like beta blockers.

Hypoglycemia unawareness puts people with type 1 diabetes at 6 times the risk of severe hypoglycemia, according to a 2015 research review.

If you experience an occurrence of nighttime hypoglycemia, you should take the same actions as you do to manage hypoglycemia in the daytime: Eat a quick-acting carbohydrate and a slow-acting carbohydrate.

If you’re caring for someone who exhibits the signs of low blood sugar, wake them up. If they wake up and can sit by themselves, give them fast-acting glucose like juice or hard candy. They should then eat a meal and test blood sugar every few hours.

If you’re caring for someone and they don’t wake up, use their emergency glucagon kit.

If there’s no kit in the home, call 911. If the person stops breathing and has no pulse, begin CPR.

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Once the person wakes up fully following the glucagon injection, they should eat a meal and test their blood sugar every few hours.

To prevent nocturnal hypoglycemia on an ongoing, long-term basis, consult a healthcare professional. You should also:

  • Test blood glucose levels before going to bed.
  • Stick to regular meals and snacks.
  • Adjust insulin dose if necessary before going to sleep.

Diabetes Canada recommends that if you’re using intense insulin therapy, you should periodically check your overnight blood glucose level at a time when your overnight insulin should be peaking. The goal is to avoid hypoglycemia during the day and lower the risk of it happening at night.

Some people with type 1 diabetes may use continuous glucose monitoring to prevent low blood sugar emergencies. A device under your skin takes a blood sugar reading every couple of minutes. You can set the device to sound an alarm when levels are too low or too high.

It’s important to contact your doctor once you know or suspect you have experienced nocturnal hypoglycemia. You and your doctor can then discuss your diabetes management plan.

Some options your doctor might suggest include:

  • Changing the dose, type, or timing of insulin.
  • Changing the dose, type, or timing of other medications.
  • Developing a new blood sugar monitoring strategy, such as continuous glucose monitoring.

You should always feel comfortable consulting with your doctor if you’d like further support in managing type 1 diabetes.

Nocturnal hypoglycemia is low blood sugar that occurs during sleep. To reduce the risk, monitor blood sugar closely and maintain an effective routine of healthy eating and insulin doses.

If you experience nocturnal hypoglycemia, work with your doctor to develop a robust management plan to prevent it from happening in the future.