What is the dawn phenomenon that some people with diabetes experience? Can anything be done about it?

Answer From M. Regina Castro, M.D.

The dawn phenomenon, also called the dawn effect, is the term used to describe an abnormal early-morning increase in blood sugar (glucose) — usually between 2 a.m. and 8 a.m. — in people with diabetes.

Some researchers believe the natural overnight release of the so-called counter-regulatory hormones — including growth hormone, cortisol, glucagon and epinephrine — increases insulin resistance, causing blood sugar to rise. High morning blood sugar may also be caused by insufficient insulin the night before, insufficient anti-diabetic medication dosages or carbohydrate snack consumption at bedtime.

If you have persistently elevated blood sugar in the morning, checking your blood sugar once during the night — around 2 a.m. or 3 a.m. — for several nights in a row will help you and your doctor determine if you have the dawn phenomenon or if there's another reason for an elevated morning blood sugar reading.

What you can do

Your doctor may recommend a number of options to help you prevent or correct high blood sugar levels in the morning:

  • Avoid carbohydrates at bedtime.
  • Adjust your dose of medication or insulin.
  • Switch to a different medication.
  • Change the time when you take your medication or insulin from dinnertime to bedtime.
  • Use an insulin pump to administer extra insulin during early-morning hours.


M. Regina Castro, M.D.

From Mayo Clinic to your inbox

Sign up for free, and stay up to date on research advancements, health tips and current health topics, like COVID-19, plus expertise on managing health.

To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and website usage information with other information we have about you. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail.

Nov. 13, 2020 See more Expert Answers

See also

  1. Medication-free hypertension control
  2. A1C test
  3. After a flood, are food and medicines safe to use?
  4. Air pollution and exercise
  5. Alcohol: Does it affect blood pressure?
  6. Alpha blockers
  7. Amputation and diabetes
  8. Angiotensin-converting enzyme (ACE) inhibitors
  9. Angiotensin II receptor blockers
  10. Anxiety: A cause of high blood pressure?
  11. Artificial sweeteners: Any effect on blood sugar?
  12. Bariatric surgery
  13. Beta blockers
  14. Beta blockers: Do they cause weight gain?
  15. Beta blockers: How do they affect exercise?
  16. Blood glucose meters
  17. Blood glucose monitors
  18. Blood pressure: Can it be higher in one arm?
  19. Blood pressure chart
  20. Blood pressure cuff: Does size matter?
  21. Blood pressure: Does it have a daily pattern?
  22. Blood pressure: Is it affected by cold weather?
  23. Blood pressure medication: Still necessary if I lose weight?
  24. Blood pressure medications: Can they raise my triglycerides?
  25. Blood pressure readings: Why higher at home?
  26. Blood pressure tip: Get more potassium
  27. Blood pressure tip: Get off the couch
  28. Blood pressure tip: Know alcohol limits
  29. Blood pressure tip: Stress out no more
  30. Blood pressure tip: Watch the caffeine
  31. Blood pressure tip: Watch your weight
  32. Blood sugar levels can fluctuate for many reasons
  33. Blood sugar testing: Why, when and how
  34. Bone and joint problems associated with diabetes
  35. Pancreas transplant animation
  36. Build resilience to better handle diabetes
  37. Caffeine and hypertension
  38. Calcium channel blockers
  39. Calcium supplements: Do they interfere with blood pressure drugs?
  40. Can whole-grain foods lower blood pressure?
  41. Caring for a loved one with diabetes
  42. Central-acting agents
  43. Choosing blood pressure medications
  44. COVID-19: Who's at higher risk of serious symptoms?
  45. Diabetes
  46. Diabetes and dental care
  47. Diabetes and depression: Coping with the two conditions
  48. Diabetes and exercise: When to monitor your blood sugar
  49. Diabetes and fasting: Can I fast during Ramadan?
  50. Diabetes and foot care
  51. Diabetes and Heat
  52. Diabetes and summer: How to beat the heat
  53. Diabetes and travel: Planning is key
  54. 10 ways to avoid diabetes complications
  55. Diabetes diet: Should I avoid sweet fruits?
  56. Diabetes diet: Create your healthy-eating plan
  57. Diabetes foods: Can I substitute honey for sugar?
  58. Diabetes and liver
  59. Diabetes management: How lifestyle, daily routine affect blood sugar
  60. Diabetes: Eating out
  61. Diabetes nutrition: Sweets
  62. Diabetes symptoms
  63. Diabetes treatment: Can cinnamon lower blood sugar?
  64. Using insulin
  65. Diabetic Gastroparesis
  66. Diuretics
  67. Diuretics: A cause of low potassium?
  68. Do you know your blood pressure?
  69. Erectile dysfunction and diabetes
  70. High blood pressure and exercise
  71. Exercise and chronic disease
  72. Fatigue
  73. Free blood pressure machines: Are they accurate?
  74. Frequent urination
  75. Home blood pressure monitoring
  76. Glucose tolerance test
  77. Glycemic index: A helpful tool for diabetes?
  78. Hemochromatosis
  79. High blood pressure (hypertension)
  80. High blood pressure and cold remedies: Which are safe?
  81. High blood pressure and sex
  82. High blood pressure: Can you prevent it?
  83. High blood pressure dangers
  84. How does COVID-19 affect people with diabetes?
  85. Hypertensive crisis: What are the symptoms?
  86. Insulin and weight gain
  87. Isolated systolic hypertension: A health concern?
  88. Kidney disease FAQs
  89. L-arginine: Does it lower blood pressure?
  90. Late-night eating: OK if you have diabetes?
  91. Low-phosphorus diet: Helpful for kidney disease?
  92. Medications and supplements that can raise your blood pressure
  93. Menopause and high blood pressure: What's the connection?
  94. Infographic: Pancreas Kidney Transplant
  95. Pancreas transplant
  96. Pulse pressure: An indicator of heart health?
  97. Reactive hypoglycemia: What can I do?
  98. Reading food labels
  99. Resperate: Can it help reduce blood pressure?
  100. Service dogs assist with diabetes care
  101. Sleep deprivation: A cause of high blood pressure?
  102. Blood sugar testing
  103. Sodium nitrate in meat: Heart disease risk factor?
  104. Stress and high blood pressure
  105. Tips for cutting costs of blood glucose test strips
  106. Unexplained weight loss
  107. Vasodilators
  108. Vegetarian diet: Can it help me control my diabetes?
  109. How diabetes affects your blood sugar
  110. How to measure blood pressure using a manual monitor
  111. How to measure blood pressure using an automatic monitor
  112. What is blood pressure?
  113. Can having vitamin D deficiency cause high blood pressure?
  114. Weight Loss Surgery Options
  115. What's your high blood pressure risk?
  116. White coat hypertension
  117. Why does diet matter after bariatric surgery?
  118. Wrist blood pressure monitors: Are they accurate?