Why is blood sugar high in the morning before breakfast

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

Answer From M. Regina Castro, M.D.

Table of Contents Show

What is the dawn phenomenon that some people with diabetes experience? Can anything be done about it?
What you can do
From Mayo Clinic to your inbox
Advertisement
How can I lower my morning fasting blood sugar?
What is a normal blood sugar level in the morning before breakfast?
How soon after waking up should I test my blood sugar?

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.

With

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

Gardner DG, et al., eds. Pancreatic hormones and diabetes mellitus. Greenspan's Basic & Clinical Endocrinology. 9th ed. New York, N.Y.: The McGraw-Hill Companies; 2011. http://accessmedicine.mhmedical.com. Accessed July 25, 2017.
McCulloch DK. Management of blood glucose in adults with type 1 diabetes mellitus. https://www.uptodate.com/contents/search. Accessed July 25, 2017.
Drug treatment of diabetes mellitus. Merck Manual Professional Version. https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/diabetes-mellitus-and-disorders-of-carbohydrate-metabolism/drug-treatment-of-diabetes-mellitus. Accessed July 25, 2017.
O'Neal T, et al. Dawn phenomenon. In: StatPearls. Treasure Island, Fla.: StatPearls Publishing; 2017. https://www.ncbi.nlm.nih.gov/books/NBK430893/. Accessed July 25, 2017.

See more Expert Answers

Medication-free hypertension control
A1C test
After a flood, are food and medicines safe to use?
Alcohol: Does it affect blood pressure?
Alpha blockers
Amputation and diabetes
Angiotensin-converting enzyme (ACE) inhibitors
Angiotensin II receptor blockers
Anxiety: A cause of high blood pressure?
Artificial sweeteners: Any effect on blood sugar?
Bariatric surgery
Beta blockers
Beta blockers: Do they cause weight gain?
Beta blockers: How do they affect exercise?
Blood glucose meters
Blood glucose monitors
Blood pressure: Can it be higher in one arm?
Blood pressure chart
Blood pressure cuff: Does size matter?
Blood pressure: Does it have a daily pattern?
Blood pressure: Is it affected by cold weather?
Blood pressure medication: Still necessary if I lose weight?
Blood pressure medications: Can they raise my triglycerides?
Blood pressure readings: Why higher at home?
Blood pressure tip: Get more potassium
Blood pressure tip: Get off the couch
Blood pressure tip: Know alcohol limits
Blood pressure tip: Stress out no more
Blood pressure tip: Watch the caffeine
Blood pressure tip: Watch your weight
Blood sugar levels can fluctuate for many reasons
Blood sugar testing: Why, when and how
Bone and joint problems associated with diabetes
Pancreas transplant animation
Caffeine and hypertension
Calcium channel blockers
Calcium supplements: Do they interfere with blood pressure drugs?
Can whole-grain foods lower blood pressure?
Central-acting agents
Choosing blood pressure medications
COVID-19: Who's at higher risk of serious symptoms?
Diabetes
Diabetes and dental care
Diabetes and depression: Coping with the two conditions
Diabetes and exercise: When to monitor your blood sugar
Diabetes and fasting: Can I fast during Ramadan?
Diabetes and foot care
Diabetes and Heat
10 ways to avoid diabetes complications
Diabetes diet: Should I avoid sweet fruits?
Diabetes diet: Create your healthy-eating plan
Diabetes foods: Can I substitute honey for sugar?
Diabetes and liver
Diabetes management: How lifestyle, daily routine affect blood sugar
Diabetes: Eating out
Diabetes nutrition: Sweets
Diabetes symptoms
Diabetes treatment: Can cinnamon lower blood sugar?
Using insulin
Diabetic Gastroparesis
Diuretics
Diuretics: A cause of low potassium?
Do you know your blood pressure?
Erectile dysfunction and diabetes
High blood pressure and exercise
Exercise and chronic disease
Fatigue
Free blood pressure machines: Are they accurate?
Frequent urination
Home blood pressure monitoring
Glucose tolerance test
Glycemic index: A helpful tool for diabetes?
Hemochromatosis
High blood pressure (hypertension)
High blood pressure and cold remedies: Which are safe?
High blood pressure and sex
High blood pressure: Can you prevent it?
High blood pressure dangers
What is hypertension? A Mayo Clinic expert explains.
Hypertension FAQs
Hypertensive crisis: What are the symptoms?
Insulin and weight gain
Isolated systolic hypertension: A health concern?
Kidney disease FAQs
L-arginine: Does it lower blood pressure?
Late-night eating: OK if you have diabetes?
Low-phosphorus diet: Helpful for kidney disease?
Medications and supplements that can raise your blood pressure
Menopause and high blood pressure: What's the connection?
Infographic: Pancreas Kidney Transplant
Pancreas transplant
Pulse pressure: An indicator of heart health?
Reactive hypoglycemia: What can I do?
Reading food labels
Resperate: Can it help reduce blood pressure?
Sleep deprivation: A cause of high blood pressure?
Blood sugar testing
Stress and high blood pressure
Unexplained weight loss
Vasodilators
Vegetarian diet: Can it help me control my diabetes?
How diabetes affects your blood sugar
How to measure blood pressure using a manual monitor
How to measure blood pressure using an automatic monitor
What is blood pressure?
Can having vitamin D deficiency cause high blood pressure?
Weight Loss Surgery Options
What's your high blood pressure risk?
White coat hypertension
Wrist blood pressure monitors: Are they accurate?

Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission.

Advertising & Sponsorship

Policy
Opportunities
Ad Choices

How can I lower my morning fasting blood sugar?

How can high blood sugar levels in the morning be controlled?.

Changing the timing or type of your diabetes medications..

Eating a lighter breakfast..

Increasing your morning dose of diabetes medication..

If you take insulin, switching to an insulin pump and programming it to release additional insulin in the morning..

What is a normal blood sugar level in the morning before breakfast?

What should your blood sugar be when you wake up? Whenever possible, aim to keep your glucose levels in range between 70 and 130 mg/dL in the morning before you eat breakfast, and between 70 and 180 mg/dL at other times.

How soon after waking up should I test my blood sugar?

In most cases, doctors ask people to measure fasting blood sugar immediately upon waking and before they have anything to eat or drink. It may also be appropriate to test blood sugar before eating or 2 hours after a meal, which is when blood sugar returns to normal levels.