Living with diabetes comes with its fair share of surprises: thirst, vision changes, dark patches of skin. But one of the biggest head-scratchers is going to bed with normal blood sugar and waking up to levels much higher than expected.
And no, this doesn’t mean you somehow sleepwalked into a midnight pantry raid or suddenly fell ill overnight. When blood glucose rises unexpectedly in the early morning hours, it’s often due to the dawn phenomenon, a natural process where hormones released before waking cause blood sugar to rise. If the body doesn’t produce enough insulin or becomes too insulin-resistant to manage this surge, glucose levels can climb.
The dawn phenomenon is a common condition, and may affect up to 50% of people living with both Type 1 and Type 2 diabetes1. If you’ve noticed unexplained morning highs, this guide will walk through what causes the dawn phenomenon, how it’s different from similar conditions, and signs to watch for so you can confidently manage your blood sugar.
Key Takeaways
Here are key things you need to know about the dawn phenomenon:
- The dawn phenomenon is a natural rise in blood sugar that happens in the early morning due to hormonal changes before waking.
- Up to half of the people with diabetes may experience this phenomenon as a common cause of high morning glucose levels.
- Morning blood sugar spikes may also be linked to other factors, including medication timing, evening eating habits, or stress.
- The Somogyi effect is another possible explanation for early-morning high blood glucose, though newer research suggests it may not be as common as previously believed.
- Simple adjustments like monitoring blood sugar, managing evening meals, and reviewing medication timing can keep morning glucose levels more stable.
What Is the Dawn Phenomenon?
The dawn phenomenon occurs when hormones released in the early morning raise blood sugar levels, as the body prepares to wake up.
Even in your sleep, your body is looking out for you, making sure there’s enough energy to start the day. In the early hours of the morning, the body releases hormones like cortisol, growth hormone, and glucagon, which signal the liver to release glucose into the bloodstream so you’re ready to wake up and get going.
To regulate this rise, the pancreas releases insulin, helping to move
glucose out of the bloodstream and into cells for energy. But for people living with diabetes, the body may not produce enough insulin, or cells may not respond effectively to the hormone. This causes glucose build-up in the bloodstream, leading to higher-than-expected blood sugar levels upon waking.
What Causes It?
The dawn phenomenon can happen when normal hormonal changes in the early morning cause blood sugar levels to rise. As your body prepares to wake up and start the day, it releases hormones such as cortisol, glucagon, growth hormone, and epinephrine to provide energy after hours of sleep and fasting. These hormones signal the liver to release glucose into the bloodstream so your body has the fuel it needs to get going.
Cortisol, often called the stress hormone, helps trigger this glucose release. Glucagon and epinephrine also play a role by prompting the liver to break down stored glycogen and release glucose into the blood. Growth hormone also contributes by temporarily reducing cells' sensitivity to insulin, allowing more glucose to remain available in the bloodstream.
Typically, the pancreas releases insulin to move this glucose from the blood into the cells for energy. But for people living with diabetes, the body may not produce enough insulin, or the cells may not respond effectively to it. When that happens, glucose can build up overnight, leading to higher blood sugar levels when you wake up.
How Common Is It?
The dawn phenomenon is very common. Up to 1 in 2 people with diabetes may notice higher blood sugar levels when they wake up, whether they have Type 1 or Type 2 diabetes. It can affect people across many age groups, including adults over 701.
What AreThe Symptoms of The Dawn Phenomenon?
- Normal or stable blood sugar levels before bed1
- Higher than usual blood sugar levels in the morning
- Elevated fasting blood glucose readings
- Worsening HbA1C levels over time
The Dawn Phenomenon vs Somogyi Effect
The dawn phenomenon doesn’t always cause high blood sugar in the morning. Sometimes, this rise may be linked to the Somogyi effect, a related but different process.
While the dawn phenomenon occurs when early-morning hormones cause more glucose to be produced as the body gears to wake up, the Somogyi effect is believed to happen when blood sugar drops too low overnight, causing the body to release hormones that push it back up. This overnight drop may be caused by taking too much insulin or not eating enough before bed2.
But while the Somogyi effect has been widely discussed, recent research using data from Continuous Glucose Monitors (CGMs) has raised questions about how often it takes place. In one study examining more than 2,600 people with type 2 diabetes, researchers found that nighttime lows followed by rebound highs were either rare or didn’t happen at all. Instead, morning spikes were more likely explained by the dawn phenomenon. Researchers are still debating exactly how common this effect is3.
How To Manage High Morning Blood Sugar
If your blood sugar tends to run high in the morning, the first step is figuring out what might be causing it. Maybe it’s related to your evening eating habits, stress levels, or the medications you take. Once you have a better sense of the cause, small adjustments can help keep glucose levels more stable overnight. The following steps can help to manage high morning blood sugar:
Eat Right At Night
What you eat, and when you eat, can influence how blood sugar behaves overnight. A lot of candy before bed, or meals high in refined carbohydrates, can cause glucose levels to rise at night and remain elevated into the morning. Swapping sweets and refined carbs for earlier-evening meals that include fiber-rich carbohydrates, protein, and healthy fats can help slow how quickly glucose enters the bloodstream4. This can help your body keep blood sugar levels steadier throughout the night.
Adjust Your Medication Time
When it comes to the dawn phenomenon, diabetes medication can sometimes feel like a double-edged sword. On one hand, it helps manage blood sugar, but if the timing isn’t right, glucose levels may start to rise overnight.
For example, taking medication too early in the evening may cause it to wear off while you sleep, which can lead to higher numbers by morning. Adjusting when you take insulin or other medications can help them work more effectively through the night5.
For the best results, make any changes with guidance from your healthcare provider so your treatment stays safe and effective.
Release Stress In The Evening
Stress can sometimes be a sneaky reason you’re waking with elevated blood sugar in the morning.
When you’re stressed, the body releases hormones like cortisol that signal the liver to release more glucose into the bloodstream, giving extra energy to respond to the stressful situation. If stress carries into the evening, it can combine with the natural early-morning hormone surge and contribute to higher blood sugar levels. Making time to unwind before bed, whether through yoga, deep breathing, and meditation, can calm the body and support steadier glucose levels overnight6.
Monitor Your Blood Sugar
Keeping an eye on your blood sugar can help you spot patterns that may be causing high readings in the morning. Checking your glucose before bed and again when you wake up can reveal whether levels are rising overnight or were already elevated before sleep.
Reliable test strips like CONTOUR® NEXT Test Strips can help you stay on top of your glucose levels, giving you the confidence to make informed adjustments to your routine. Designed for accuracy, they support more reliable readings to help you manage diabetes day to day.
FAQs
Can I Prevent The Dawn Phenomenon?
Because the Dawn Phenomenon is driven by natural hormonal changes, early-morning blood sugar spikes may not always be completely preventable. But by adjusting your medication timing, choosing balanced evening meals, and monitoring blood sugar levels, you can reduce its impact. Working with a healthcare provider can also help you find the approach that keeps your morning glucose levels more stable.
What Is The Somogyi Effect?
The Somogyi effect refers to high morning blood sugar that may follow a drop in glucose during the night. When blood sugar falls too low, the body releases hormones that push glucose levels back up. This response can cause elevated readings in the morning.
Is The Dawn Phenomenon Dangerous?
The dawn phenomenon isn’t necessarily dangerous. However, consistently high blood sugar levels over time can lead to complications such as nerve damage, kidney disease, and vision problems. Working with a healthcare provider to adjust medication, meals, or monitoring routines can help keep morning blood sugar within a healthy range.
Does The Dawn Phenomenon Affect Type 1 and Type 2 Diabetes Differently?
The dawn phenomenon can occur in both Type 1 and Type 2 diabetes, but for slightly different reasons. In Type 1 diabetes, the body cannot produce enough insulin to offset the early-morning release of glucose from the liver. In Type 2 diabetes, insulin is still released, but insulin resistance makes it harder for cells to use glucose effectively, causing blood sugar levels to increase upon waking.
This content is for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always seek the advice of a qualified physician or health provider with any questions regarding a medical condition. Never disregard professional medical advice or delay seeking it because of information read here.
References:
- O'Neal TB, Luther EE. Dawn Phenomenon. [Updated 2023 May 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430893/
- Reyhanoglu G, Rehman A. Somogyi Phenomenon. [Updated 2023 May 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK551525/
- Huang, Y., Lou, X., Huang, W., Qiu, J., Jiang, C., Sun, J., & Tao, X. (2022). Confirmation of the Absence of Somogyi Effect in Patients with Type 2 Diabetes by Retrospective Continuous Glucose Monitoring Systems. International journal of endocrinology, 2022, 6599379. https://doi.org/10.1155/2022/6599379
- Reynolds A, Mitri J. Dietary Advice For Individuals with Diabetes. [Updated 2024 Apr 28]. In: Feingold KR, Adler RA, Ahmed SF, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279012/
- American Diabetes Association. (n.d.). High morning blood glucose. https://diabetes.org/living-with-diabetes/high-morning-blood-glucose
- National Library of Medicine. (2024, September). High blood sugar (hyperglycemia). MedlinePlus. https://medlineplus.gov/ency/patientinstructions/000874.htm