Having low blood sugar levels can cause unpleasant symptoms and can be potentially dangerous.
It’s estimated that half of all episodes of low blood sugar and more than half of severe episodes of low blood sugar occur at night.
Low blood sugar at night is called nocturnal hypoglycemia.
We’ll discuss low blood sugar overnight in depth in this article, including ways to prevent it from happening to you.
What is nocturnal hypoglycemia?
Hypoglycemia is the term for low blood sugar, which occurs in people with type 1 and type 2 diabetes. It is defined as a blood glucose level below 70 mg/dL. Hypoglycemia is considered severe when blood sugar drops below 54 mg/dL.
People without diabetes can also develop low blood sugar, but it isn’t as common as in people with diabetes.
Nocturnal hypoglycemia is when your blood sugar level drops at night, usually when you’re sleeping (1). Nocturnal hypoglycemia can be more dangerous than hypoglycemia during the day because you might not be awake or aware of the symptoms.
Signs of low blood sugar
Some of the more common hypoglycemia symptoms include:
- Feeling shaky and/or dizzy
- Rapid and/or irregular heartbeat
- Pale skin
- Tingling or numbness of the lips, tongue, or cheek
- Feeling irritable or moody
- Feeling anxious or nervous
Since you might not be awake or alert enough to notice the typical hypoglycemia symptoms, there are specific symptoms of nocturnal hypoglycemia to watch out for:
- Damp sheets or nightclothes from sweating due to low blood sugar
- Feeling tired, irritable, or confused after waking up
You might wonder how you can find out if you have nocturnal hypoglycemia if you’re asleep. If you suspect you might be getting nocturnal hypoglycemia, try waking up and checking your blood sugar in the middle of the night, such as 2:00 or 3:00 AM.
Using a continuous glucose monitor (CGM) is especially helpful in identifying low blood sugar overnight. You can set alarms on a CGM so it will notify you when your blood sugar falls below a certain threshold.
What causes blood sugar to drop at night?
1) Too much insulin at bedtime
If you’re taking insulin to treat your diabetes, you have a higher risk of developing low blood sugar overnight than those who take other diabetes medications.
Basal insulin, or long-acting insulin, is usually taken once or twice per day. Examples of basal insulin include Levemir, Lantus and Semglee. If you take insulin at bedtime, you might develop low blood sugar at night if your dose is too high.
2) Not eating enough carbohydrates
Carbohydrates are one of three main nutrients you get from food (the others are protein and fat). Carbs break down into glucose, which raises your blood sugar.
If you don’t eat enough carbohydrates throughout the day and take a diabetes medication (especially insulin), you might develop nocturnal hypoglycemia. The carbohydrate content of your last meal or snack of the day plays the largest impact on nighttime blood sugar levels.
Exercising helps lower your blood sugar levels. Both cardiovascular/aerobic and weight lifting exercises can lower blood sugar, which can occur up to 24 hours after you finish your exercise routine.
If you exercise in the evening, you might develop low blood sugar overnight as your body replenishes depleted glycogen (stored sugar) in your liver.
4) Drinking alcohol
Drinking alcohol depletes your body’s glycogen stores and can lead to hypoglycemia. You’re at a greater risk of developing nocturnal hypoglycemia if you drink excessive amounts of alcohol before bedtime, especially if you also take insulin or blood sugar-lowering medications.
5) Severe infections
Hypoglycemia can be a sign of a serious infection, such as sepsis. If you’re experiencing nocturnal hypoglycemia and are also ill, it could be related.
What happens if blood sugar gets too low while sleeping?
If your blood sugar levels drop while you’re sleeping, you might not be able to correct them as soon as you would in the daytime.
Left untreated, hypoglycemia can become dangerous and cause symptoms like:
- Clumsiness or jerky movements
- Muscle weakness
- Slurred speech or difficulty speaking
- Blurred vision or double vision
- Convulsions or seizures
If you become dizzy from hypoglycemia, you could lose consciousness and could fall and injure yourself. Without the ability to communicate (such as slurred speech, confusion, etc.) and being alone, your low blood sugar could become severe.
How to prevent low blood sugar overnight: 7 tips
1) Check your blood sugar before bedtime
Checking your blood sugar before bedtime will give you an idea of your blood sugar before you sleep.
If your blood sugar is on the lower side (such as below 100 mg/dL), you might be instructed by your healthcare provider to eat a carbohydrate-containing snack or reduce or omit your nightly insulin dose, if applicable.
2) Adjust your insulin regimen (if applicable/necessary)
If you’re taking insulin, you might need to adjust your dose if you repeatedly experience nocturnal hypoglycemia.
You should check your blood sugar before bed if you’re taking short-acting insulin (such as Humalog or Novolog) with your last meal. If it’s on the lower side, you might need to reduce your dinnertime insulin dose.
Long-acting insulin doses at bedtime might also need to be reduced for persistent nocturnal hypoglycemia. You can adjust your insulin doses under the guidance of your healthcare provider.
If you use an insulin pump, the settings can be adjusted so that your background/basal insulin delivery rate is lower while you’re sleeping to prevent low blood sugar overnight.
3) Avoiding nighttime exercise
You might consider experimenting with morning exercise instead of exercising before bed. If you’re exercising before bed, the timing of your blood sugar lowering can fall at nighttime and cause nocturnal hypoglycemia.
4) Eat a carbohydrate-based bedtime snack
Eating a bedtime snack containing carbohydrates (15-30 grams) can help prevent nocturnal hypoglycemia.
A piece of toast, several crackers, a glass of regular (cow’s) milk, or a small cup of fruit all provide carbohydrates that can help raise your blood sugar before bedtime and potentially prevent low blood sugar overnight.
5) Be ready to treat low blood sugar
If you catch nocturnal hypoglycemia in its early stages, you can help prevent it from becoming severe. If your blood glucose is below 70 mg/dL, consume 15 grams of carbohydrates and then recheck your blood sugar in 15 minutes. You should repeat this process until your blood glucose is above 70 mg/dL.
You can get 15 grams of carbohydrates from:
- ½ cup of juice
- 15 jelly beans
- 1 tablespoon of honey
- Four glucose tablets (containing 4 grams of carbs each)
Having these types of items at your bedside can help you treat low blood sugar more quickly if it occurs at nighttime.
If you have a history of low blood sugar, you might be prescribed glucagon, an injectable hormone that raises your blood sugar.
6) Eat regular meals and snacks
Eating enough carbohydrates throughout the day can help keep your blood sugar levels more stable. If you skip meals or snacks, you might develop low blood sugar later in the day.
This is especially important if you’re taking insulin or another diabetes medication that can cause hypoglycemia, such as sulfonylureas.
7) Consider a continuous glucose monitor
If you have repeated hypoglycemia (nocturnal or otherwise) despite lifestyle and medication changes, you might be a good candidate for a continuous glucose monitor.
A CGM is also beneficial for other blood sugar problems like the Dawn Phenomenon, which is when morning blood sugar levels are high.
CGMs continually measure your blood sugar levels every minute to every few minutes. CGMs can alert you if your blood sugar is trending downward or if it falls below a determined threshold.
Using a CGM gives you more feedback in real-time compared to checking your blood sugar with a standard glucometer. A CGM can help you make adjustments to avoid nighttime lows.
Nocturnal hypoglycemia is when you develop hypoglycemia at night, usually when you’re asleep. Nocturnal hypoglycemia can be more dangerous than daytime hypoglycemia because you might not be awake to notice the symptoms of low blood sugar.
The best ways to avoid nocturnal hypoglycemia are to check your blood sugar levels before bedtime, make any necessary medication changes, eat carbohydrates consistently (especially in the evening), and avoid exercising before bed.
A continuous glucose monitor can also be a useful tool in identifying blood sugar trends like nighttime low blood sugar.
If you have persistent nocturnal hypoglycemia, you should seek advice from your healthcare provider.