High Blood Sugar at Night: What to Do

Why do your blood sugar levels increase at night, and what you can do to prevent this? Learn strategies for managing high blood sugar levels overnight and in the morning, including healthy bedtime snacks.

For National Sleep Awareness week, we are focusing on how to regulate overnight blood glucose (sugar) levels. With the many factors that can affect your glucose levels, nighttime can be a challenge. Some people with diabetes experience high overnight levels while others fear or experience a glucose drop during sleep. Trying to keep glucose levels stable overnight will help you get more sleep and feel better – and a good night’s sleep will aid your diabetes management the next day. While this article focuses on overnight highs, you can learn more about preparing for and preventing hypoglycemia (low blood sugar) here.

Here are some tips and strategies for how people living with diabetes can get better sleep at night and avoid high blood sugar levels. 

Symptoms of High Blood Sugar at Night

If your blood sugar is high at night you may experience symptoms of hyperglycemia. Hyperglycemia, or “high glucose,” is not defined by one specific glucose level. While many people with diabetes aim to keep blood sugar levels below 180 mg/dl during the day, some people aim for the lower range of 120 or 140 mg/dl at night, when they are not eating.

At night, symptoms of hyperglycemia include: 

• Poor sleep

• Waking up often to urinate or to drink water

• Headache

• Dry mouth

• Nausea

Other symptoms of hyperglycemia that you may experience during the day or night include: 

• Frequent and excessive urination 

• Extreme thirst 

• Blurry vision 

• Confusion

• Weakness 

• Shortness of breath

Is It Safe to Sleep with High Blood Sugar?

Glucose levels that are occasionally a little high at night generally don’t pose serious, immediate health concerns. Most people with diabetes cannot avoid some high glucose levels. However, frequent or long-term highs – particularly extremely high levels (above 250 mg/dl) – can be dangerous. It is important for people with diabetes to reduce high blood sugar as much as possible for two key reasons:

1. Frequent hyperglycemia can lead to major health complications caused by damage to blood vessels and nerves, which can affect your eyes, heart, kidneys, and other organs. This occurs when glucose levels are too high over a long period of time.

2. Very high glucose levels can be a sign of diabetic ketoacidosis (DKA, or high levels of ketones in your blood indicating that there is not enough insulin in your body). This occurs mainly in people with type 1 diabetes and can be life-threatening. For more information on DKA, read “Ketosis vs. Ketoacidosis: What’s the Difference.”

Why Does Blood Sugar Go Up at Night? 

There are many factors that can cause your blood sugar to increase at night. For example: what food you ate during the day, how much and when you exercised, whether you ate snacks before bed, the timing of your insulin doses, and your stress level. You can experience different patterns of high blood sugar at night. You may start with high glucose when you go to bed, start the night in range but go high several hours later, or spend most of the night in range until the hours just before you wake up. By identifying your body’s patterns, you can figure out what is causing your high blood sugar and how to address it.

Common causes of a glucose increase at night include:

• Eating too close to bedtime: whether you’re snacking or eating a late dinner, a post-meal glucose spike can lead to high glucose levels overnight. In particular, high-fat, high-carb meals (like pizza or pasta with creamy sauces) might delay glucose absorption causing an extended period of high blood sugar levels.

• If you have type 2 diabetes, a treatment plan that doesn’t adequately address your nighttime insulin resistance or missed doses of your glucose lowering medication can cause high glucose levels at night (and often also during the day).

• Over-correcting a low glucose level before bed. If you need to bring your glucose level back into range before you sleep, take just enough glucose to stabilize your blood sugar. Quantity-limited treatments (like glucose tablets or small candies) that will raise your glucose levels by a specific amount can be very helpful – learn more here. 

• If you take insulin, your insulin levels may be inadequate during the night. Depending on your dose and timing of basal insulin, the insulin may not last in your body until the morning. Learn about different types of insulin, insulin pumps, and automated insulin delivery (AID) systems, all of which can be helpful for staying in your target glucose range overnight.

• Taking less insulin before bedtime due to fear of low blood sugar overnight.

What is the Dawn Phenomenon?

Another reason for high nighttime blood sugar levels is the “dawn phenomenon.” The dawn phenomenon occurs early in the morning when the body naturally signals your liver to produce glucose, giving your body the energy it needs to wake up.

The hormonal changes associated with the dawn phenomenon happen to people with or without diabetes, though those without diabetes do not experience hyperglycemia. If you take insulin, you may need to try a new basal insulin or adjust the timing and amount of your basal dose (with injected insulin) or your nighttime basal rates (with an insulin pump) to cover an early morning rise. 

How to Stabilize Your Blood Sugar Overnight

The most important thing you can do to stabilize your blood sugar is monitor your glucose levels at bedtime, during the night, and when you wake up to look for patterns. This will help you determine what’s going on in your body and how you can fix it. While there are many strategies people use to stabilize blood sugar at night, every person is different – you’ll have to look for trends in your body, experiment with ways to lower glucose levels over a period of time, and learn what works best for your body.

• Check your blood sugar (or CGM) before bed. If it’s already high, your blood sugar levels may remain high throughout the night. To address this, you’ll want to start by adjusting when you eat your evening meal and what it consists of, and how much mealtime insulin you take to cover it.

  • Avoid eating lots of food close to bedtime. For diaTribe writer Adam Brown, the key to staying in range overnight is low-carb, early dinners, with no snacking after dinner.

  • Consider eating less food at night and taking more basal insulin to cover your evening meal.

• Check your blood sugar (or CGM) during the night, between midnight and 3am. If you were in range before bed but have high glucose levels between midnight and 3am, you may need to adjust your basal insulin dosage and timing. If you are low during that time, you may experience a rebound high blood sugar later on – this is usually associated with overcorrecting the low.

  • Talk with your healthcare team about the optimal nighttime insulin regimen for you. You may need to adjust your insulin to avoid both early low blood sugar and later high blood sugar.

  • If you take basal insulin, see if you’re able to get an insulin pump or an automated insulin delivery (AID) system. AID systems will automatically adjust your basal insulin doses throughout the night to help keep your glucose levels stable.

  • For some people, a small snack before bed (with a small dose of insulin, if appropriate) can help stabilize glucose levels throughout the night and avoid an early morning high. Keep reading for a list of healthy bedtime snacks.

• Check your blood sugar (or CGM) when you wake up. If you were in range before bed and between midnight and 3am, but have high blood sugar in the morning, you may be experiencing the dawn phenomenon or running out of insulin (or other medication). 

  • If you take insulin, you may need to delay the timing of your basal dose to as close to bedtime as possible. Or, you may increase your basal rates with an insulin pump from around 3am on. 

  • If you have type 2 diabetes, talk with your healthcare professional about your glucose-lowering medications to make sure that your treatment plan addresses overnight hyperglycemia.

It’s possible to experience a combination of these events – you may have high blood sugar levels at various points throughout the night. If you have a continuous glucose monitor (CGM, you’ll be able to better track your glucose levels throughout the night. You can use your CGM data to relate your behaviors to patterns in your nighttime glucose levels. Does the timing of physical activity affect your glucose levels overnight? What about food choices throughout the day, in terms of type, quantity, or timing of food? If you don’t have a CGM, the more frequently you can take a blood sugar readings the better. Learn how to get the most of your fingerstick blood sugar data here. It’s important to share your nighttime glucose observations with your healthcare team so that you can find the best ways to stabilize your blood sugar over the entire night.

For more advice on stabilizing nighttime glucose levels, read Adam Brown’s “The Overnight Blood Sugar Conundrum.”

Great Bedtime Snacks for People Living with Diabetes

For some people, a healthy bedtime snack helps to prevent glucose swings during the night. By eating a small snack that is full of protein and healthy fats (and low in carbohydrates), your body may be better able to avoid an overnight high – but if you take insulin, be sure to cover the carbohydrates in your snack even if it only requires a small dose of insulin.

Here are some snack ideas:  

• Plain nuts or seeds – try eating a small handful

• Raw vegetables, such as carrots, celery, cucumbers, or tomatoes, with a small amount of hummus or peanut butter

• Plain yogurt, and you can add berries or cinnamon (read about choosing a healthy yogurt here)

• Chia seed pudding

Remember, a bedtime snack is only helpful for some people. To see if it works for you, you’ll have to carefully monitor your glucose before bed, during the night, and when you wake up.

What Should Your Blood Sugar Be When You Wake Up?

The goal of diabetes management is to keep your blood sugar levels as stable as possible. This means that when you wake up, you want your glucose to be in range and to stay in range throughout the day.

For many people with diabetes, the overall target glucose range is between 70 mg/dL to 180 mg/dL (3.9 to 10.0 mmol/L). To start the day strong, the American Diabetes Association recommends that you aim to wake up with glucose levels between 80 to 130 mg/dL. Talk with your healthcare team about your glucose targets.

How to Lower Morning Blood Sugar

Whether a morning high is caused by the dawn phenomenon or something else, here are a few things you can try to lower your blood sugar levels:

• Physical activity when you wake up can help bring your glucose level down. Even going for a walk can be helpful.

  • To learn about exercise guidelines and glucose management strategies, click here.

  • Read Adam Brown’s take on walking – the most underrated diabetes exercise strategy.

• Eating a light breakfast can help keep a morning high from increasing even more. Taking your mealtime insulin will help lower your blood sugar.

  • Adam Brown suggests eating a breakfast that is low in carbs, and notes that sometimes mealtime insulin has to be adjusted in the morning. One of his favorite breakfasts is chia pudding, since it has little impact on glucose levels; see what else he eats for breakfast here.

  • Catherine Newman has six popular, low-carb, delicious recipes in “The Morning Meal.”

• Intermittent fasting and time-restricted feeding approaches to meal timing can also help people keep morning blood sugar levels in range. Read Justine Szafran’s “Intermittent Fasting: Stabilizing My Morning Blood Sugars” to learn more.

• For additional ways to navigate mornings, read seven strategies from Adam Brown in “A Home Run Breakfast with Diabetes.”

This article is part of a series on time in range. 

The diaTribe Foundation, in concert with the Time in Range Coalition, is committed to helping people with diabetes and their caregivers understand time in range to maximize patients’ health. Learn more about the Time in Range Coalition here.

About the authors

Eliza Skoler

Eliza Skoler joined The diaTribe Foundation in 2019, after graduating cum laude from Carleton College with a degree in Biology. Her undergraduate studies focused on human biology and neuroscience, and... Read the full bio »