Introduction
Some people living with diabetes may check their blood glucose (blood sugar) first thing in the morning and be surprised to find that it is higher than expected, even though they have not eaten overnight. This is a common experience and may be related to the Dawn Phenomenon.
This article explores what the Dawn Phenomenon is, why it happens, and how it differs from other causes of high morning blood glucose. It also discusses practical strategies for managing elevated morning blood glucose levels, when it may be time to talk with a healthcare provider, and important questions to consider asking during a healthcare appointment.
What Is the Dawn Phenomenon?
The Dawn Phenomenon is a natural rise in blood glucose that occurs in the early morning hours, typically between 4:00 a.m. and 8:00 a.m. During the early morning hours, the body naturally releases several hormones to help one wake up and prepare for the day. These “wake-up hormones” include:
- Cortisol
- Growth hormone
- Glucagon
- Epinephrine (adrenaline).
These hormones signal the liver to release stored glucose into the bloodstream, providing the body with a source of energy to start the day. In people without diabetes, the pancreas responds by secreting (making) and releasing the hormone insulin to keep blood glucose levels within a healthy range.
But for those with diabetes, the body may not produce enough insulin or may not use insulin effectively. As a result, the glucose released by the liver remains in the bloodstream, leading to higher-than-expected blood glucose levels upon waking.
Read more about hormones and their impact on health.
Causes of the Dawn Phenomenon
The specific causes of the Dawn Phenomenon are not fully understood, but evidence suggests that the morning high blood sugars associated with this phenomenon could be due to the following factors:
- Not getting enough insulin in the evening
- Not getting the right dose of diabetes medicines before bedtime
- Eating a carbohydrate-heavy snack ahead of bedtime
Signs You May Be Experiencing the Dawn Phenomenon
If you think you may be experiencing the Dawn Phenomenon, there are several common signs to watch for. While everyone’s blood glucose patterns are different, the following clues may indicate that the Dawn Phenomenon is contributing to your elevated morning blood glucose levels:
- Higher-than-expected blood glucose reading when one wakes up, even though one’s bedtime blood glucose reading was within target range.
- Consistently elevated morning blood sugar over several days rather than an occasional high reading.
- No food or snacks were consumed overnight.
- Blood glucose levels that rise between approximately 4:00 a.m. and 8:00 a.m., as shown by a continuous glucose monitor (CGM) or by checking one’s blood glucose overnight.
- Morning blood glucose that remains elevated despite following one’s usual diabetes management routine, including taking medications as prescribed and eating balanced meals.
If one notices these patterns, keeping a record of one’s blood glucose readings for several days and sharing them with a qualified healthcare provider can help identify when one’s blood glucose begins to rise and determine whether the Dawn Phenomenon is the cause. This can help guide decisions about one’s diabetes management plan.
The Difference Between the Dawn Phenomenon and the Somogyi Effect (Rebound hyperglycemia)
While the Dawn Phenomenon is a common cause of elevated morning blood glucose, it is not the only possible explanation. Another pattern that can produce similar morning readings is the Somogyi Effect, also referred to as rebound hyperglycemia (rebound high blood sugar). Unlike the Dawn Phenomenon, the Somogyi Effect is thought to occur when blood glucose drops too low during the night. In response, the body releases hormones that stimulate the liver to release stored glucose, causing blood glucose levels to rebound and appear elevated by morning.
Because these two patterns have different underlying causes, identifying the reason for elevated morning blood glucose can help a qualified healthcare provider, such as an Endocrinologist (Endo.), Medical Doctor (MD), Doctor of Osteopathic Medicine (DO), Physician’s Assistant (PA), or Nurse Practitioner (NP), or a Certified Diabetes Care and Education Specialist (CDCES), determine the most appropriate management plan. A healthcare provider may recommend checking blood sugar during the night or reviewing data from a continuous glucose monitor (CGM) to better understand overnight blood glucose patterns before making changes to a diabetes self-management plan. Understanding these patterns can help individuals and their healthcare providers work together to keep blood glucose within the recommended target ranges.
Key characteristics of the Somogyi Effect:
- Blood glucose falls too low overnight (hypoglycemia).
- The body responds by releasing hormones that raise blood glucose.
- Morning blood glucose may be elevated following nighttime hypoglycemia.
- May be associated with too much evening insulin, certain diabetes medications, delayed meals, increased physical activity, or alcohol consumption before bedtime.
The best way to distinguish between the Dawn Phenomenon and the Somogyi Effect is to identify what happens to your blood glucose overnight and share the pattern with one’s healthcare provider. One’s healthcare provider may recommend:
- Check blood glucose levels around 2:00–4:00 a.m. for several nights.
- Reviewing data from a continuous glucose monitor (CGM) if one is used.
- Looking for patterns rather than relying on a single morning blood sugar reading.
Understanding the cause of high morning blood glucose is important because the management strategies and plans one may employ can differ. Before making changes to medications, insulin, or bedtime routine, ALWAYS discuss one’s blood sugar patterns with a qualified healthcare provider such as MD, DO, Endo., FNP, or PA.
Why Managing Morning Blood Sugar Matters
Managing morning blood glucose is an important part of one’s diabetes self-management plan, as fasting blood glucose often sets the tone for the day’s blood glucose readings. Elevated morning blood glucose readings may be caused by the Dawn Phenomenon, insufficient overnight insulin, evening food choices, or other personal factors. However, when consistently elevated, high morning blood sugar can make it more difficult for an individual to reach their A1C goal.
Benefits to Managing Morning High Blood Sugar
- Improves A1C
- An individual’s A1C is an average of their blood glucose over a 2–3-month period. A high A1C reading indicates a high percentage of sugar molecules that remain in the bloodstream.
- Over time, an elevated A1C can put immense stress on the body’s blood vessels, as well as organs such as the heart and kidneys. This stress can damage the body’s systems, leading to plaque buildup, elevated cholesterol levels, and high blood pressure, which can place further stress on vital organ systems and develop chronic disease conditions such as chronic kidney disease or heart disease.
- Striving to meet a targeted fasting blood glucose level can help lower one’s A1C.
- One with diabetes should aim for a fasting blood glucose (8 hours without eating or drinking) between 80-130 mg/dL, the range established by the American Diabetes Association or the targeted range set by your physician.
- Supports Stable Blood Sugar Throughout the Day
- Starting with a blood glucose closer to one’s targeted range may make it easier to maintain healthy blood glucose levels throughout the day! It may also reduce large blood sugar fluctuations (changes) can occur when blood glucose is already elevated upon waking
- May Reduce the Risk of Diabetes Related Complications
- This may include:
- Heart disease and stroke
- Chronic Kidney Disease (nephropathy)
- Eye disease (retinopathy)
- Nerve damage (neuropathy)
- Poor wound healing
- This may include:
Practical Strategies to Manage the Dawn Phenomenon and Morning Blood Sugar
1. Review Evening Meals
One of the biggest contributing factors to one’s daily blood glucose readings is how one fuels their body. Checking blood sugar levels before and after meals is a great step to understand how the food one consumes impacts blood glucose. Using this, individuals with diabetes who are managing blood sugar levels can make more informed, confident decisions at mealtimes and choose foods that best support blood glucose balance. For most people with diabetes, following the Plate Method is a great first step toward understanding diabetes nutrition. The Plate Method focuses on:
- ½ of the plate filled with non-starchy vegetables
- ¼ of the plate filled with a high-quality source of protein
- ¼ of the plate filled with a carbohydrate forward food or starchy vegetables
Read more about nutrition recommendations for diabetes.
Other strategies for nutrition during the day include:
- Limiting sugary snacks and beverages before bed
- If one needs a snack before bed, consider trying a snack with a good source of protein and light carbohydrates.
- Examples:
- Apple slices with peanut butter
- Greek yogurt with berries
- Whole-grain crackers with cheese
- Examples:
2. Increase Physical Activity
- Physical activity can improve insulin sensitivity (how well the body uses insulin) and help lower blood glucose levels.
- Aim for at least 150 minutes of moderate physical activity per week.
- Examples for achieving this may include:
- Evening walk after dinner
- Light resistance exercises
- Regular daily movement
- Examples for achieving this may include:
Read more about cardiovascular training.
Read more about strength training.
3. Prioritize Quality Sleep
- Poor sleep can increase stress hormones and contribute to higher blood glucose levels.
- Consider practicing healthful sleep habits such as:
- Maintaining a consistent bedtime routine
- Practicing good “sleep hygiene” – the practice of developing good environmental habits that support adequate sleep.
Read more about getting restful sleep with diabetes.
4. Talk With a Healthcare Provider
- If one is continuously struggling with morning high blood glucose, it is important to speak with a healthcare provider.
- One’s provider may recommend:
- Adjusting medication timing
- Reviewing insulin doses
- Exploring new treatment options
- Important: NEVER change medications without professional guidance.
- Contact a healthcare provider if:
- Morning blood glucose readings are consistently above target range
- Go to your appointment with a daily blood sugar log, including fasting blood sugars
- One is experiencing symptoms of high blood glucose
- One is noticing frequent overnight low glucose readings
- One has concerns about medication effectiveness
- Morning blood glucose readings are consistently above target range
Conclusion
The Dawn Phenomenon is a common and normal biological process that can affect people living with diabetes. Understanding why it happens can help an individual take steps to better manage blood glucose levels. Tracking blood sugar patterns, making lifestyle adjustments, and working with one’s healthcare team can help someone living with diabetes start the day with better blood glucose control and reduce the subsequent impact of long-term high blood glucose levels.
References
- American Diabetes Association. (N.D) High morning blood glucose: Understanding and management. Retrieved from https://diabetes.org/living-with-diabetes/high-morning-blood-glucose
- Cleveland Clinic. (2022). Dawn phenomenon. Retrieved from https://my.clevelandclinic.org/health/diseases/24553-dawn-phenomenon
- Cleveland Clinic. (2023). Somogyi effect. Retrieved from https://my.clevelandclinic.org/health/diseases/11443-somogyi-effect
- Cleveland Clinic. (2026). Hypoglycemia (low blood sugar). Retrieved from https://my.clevelandclinic.org/health/diseases/11647-hypoglycemia-low-blood-sugar
- Mayo Clinic. (2026). The dawn phenomenon: What can you do? Retrieved from https://www.mayoclinic.org/diseases-conditions/diabetes/expert-answers/dawn-effect/faq-20057937
Author
- Julianna Lyle, Rural Health and Nutrition Extension Team, Anderson & Abbeville Counties
Reviewed By
- Michelle Altman, Extension Associate, Rural Health and Nutrition
- Melissa Bales, Extension Associate, Rural Health and Nutrition
- Ellie Lane, Extension Associate, Rural Health and Nutrition
