Why is my blood sugar high in the morning?

People with Type 1 or Type 2 diabetes benefit from keeping blood sugar in the target range, or normal range. Maintaining tight control of blood sugar helps prevent both short-term and long-term complications and is best for overall health. Sometimes, people with diabetes wake up with hyperglycemia (high blood glucose). This can be extra frustrating, especially because you may spend a lot of time during the day focusing on diet and exercise, taking your insulin or oral medicines as prescribed, and testing your blood sugar—then waking up with a high blood sugar level. 

What is the cause of early morning high blood sugar? There are several potential causes. One common cause is the dawn phenomenon, where hormones signal the liver to increase glucose (sugar) production in the early morning hours. Continue reading to learn more about the dawn phenomenon as well as other causes of high morning blood sugar. 

What causes high blood sugar in the morning?

You know the feeling—you do everything right. You eat well-balanced meals, squeeze in physical activity, test your blood sugar regularly (or wear a continuous glucose monitor), and take your medication or insulin exactly as directed. So why do you wake up with a blood sugar that is higher than your normal range? For adults with diabetes, a general target number for morning (fasting) blood sugar is 80 to 130 mg/dl. For adults who do not have diabetes, this target blood sugar level is less than 100 mg/dl. Fasting blood sugar is the blood sugar level when you have not had anything to eat or drink, except water, for eight to 12 hours. There can be several possible reasons for high morning blood sugar. Testing your blood sugar frequently or wearing a continuous glucose monitor (CGM), and sharing the data with your diabetes care team, will help you identify what is causing high blood sugar in your situation. 

The dawn phenomenon

In the early hours of the morning, hormones (including cortisol and growth hormone) tell the liver to increase glucose production, which helps give you the energy to wake up and start your day. This sugar production triggers the beta cells in the pancreas to release insulin, which helps keep blood glucose levels under control. But, people with diabetes may not produce enough insulin—or may be too insulin resistant—to battle the higher blood sugar, so you may have more elevated blood sugar between 3 am and 8 am. This dawn phenomenon can occur in people with either Type 1 or Type 2 diabetes. If your blood sugar levels are high in the hours just after midnight, the dawn phenomenon may be the cause of your high morning blood sugar. 

Waning insulin

If you do not get enough insulin overnight while you sleep, your blood sugar will rise, and you will wake up with high blood sugar. This can occur if your basal insulin (background insulin) is too low, regardless of whether you get basal insulin through an insulin pump or inject long-acting insulin. If your blood sugar levels are in range at bedtime, waning insulin could be the cause of your high morning blood sugar.

The Somogyi effect

A less common reason for a high morning blood glucose level is the Somogyi effect. The Somogyi effect was named after a chemist named Michael Somogyi, Ph.D., who first described this occurrence. The Somogyi effect is as follows: your blood sugar dips too low overnight, which may occur after you skip a meal or take too much insulin in the evening. This hypoglycemia (low blood glucose) triggers the body to make more glucose, and as a result, you wake up with high blood sugar.

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

Adults with diabetes will generally aim for a target fasting blood sugar of 80-130 mg/dl—however, individuals may vary slightly in their targets due to the recommendations of their healthcare professionals. The best time to check your fasting blood sugar is when you wake up, before you have anything to eat or drink (besides water). 

Consult your healthcare provider or another member of your diabetes care team, such as your Certified Diabetes Care and Education Specialist (CDCES), who can help you pinpoint the reason for high morning blood sugar. Although the dawn phenomenon, waning insulin, and Somogyi effect are the most common causes of high morning blood sugars, other variables can also cause blood sugar, including morning blood sugar, to spike, such as high-carbohydrate bedtime snacks. Figuring out what is affecting your morning blood sugar level can help you determine steps you can take to get this number into the normal range. Always discuss steps with your healthcare provider and do not change doses of medication or insulin unless directed by your healthcare provider.

If your high morning blood sugar is due to the dawn phenomenon, you may need to adjust the timing or dose of your diabetes medications, eat a breakfast with lower carbohydrates, or switch to an insulin pump with a program set to release more insulin in the early morning hours when you need more blood sugar control.

If your high morning blood sugar is due to waning insulin, you can consult your healthcare provider about your insulin regimen. You may benefit from changing the time of your injection, or switching to an ultra-long-acting insulin (such as Tresiba) or a basal insulin that can be dosed twice daily (like Levemir). 

If your high morning blood sugar is due to the Somogyi effect, you may need to add a snack before bed that contains carbohydrates and avoid exercising several hours before bedtime. You may need to decrease the dose of medications that are causing low blood sugar levels overnight. If you use insulin, your healthcare professional may recommend switching to an insulin pump with a program set to administer less insulin overnight when your blood sugar is low. 

Other ways to control high blood sugar levels

It is important to maintain tight control of blood sugar levels as much as possible. Here are some general tips on how to keep blood sugar in your target range:

• Get regular physical activity—at least 150 minutes per week (that could be broken down into 30 minutes, five times a week) of moderate-intensity physical activity, plus two weekly strength training sessions. Check with your healthcare professional before starting a new exercise program. And follow your treatment plan guidance on testing ketones before exercise—if your blood sugar is 240 mg/dl or more, you’ll need to test ketones before exercising. If ketones are present, you should not exercise. Contact your healthcare provider for medical advice.
• Take your oral diabetes medication and/or insulin exactly as directed, and do not skip doses. Many patients have difficulty affording their medications, so if cost is a concern, ask your healthcare provider or pharmacist about the best ways to save, such as choosing generic drugs, using manufacturer coupons on brand-name drugs or insulin, and accessing a free SingleCare discount card.
• Follow your healthcare provider’s recommendations on lifestyle changes such as diet, or consult a registered dietician specializing in prediabetes and diabetes nutrition. Eat healthy, well-balanced meals at regular intervals. Drink plenty of water, avoiding sugary beverages such as fruit juices and regular sodas (unless you need to treat lows!). Bonus—drinking water can help control your blood sugar.
• Check your blood sugar as directed by your physician. If you are reluctant to finger stick, ask your doctor about a CGM, which mostly eliminates the need for finger sticks. 
• Be sure you understand your diabetes treatment plan, including what to do if your blood sugar is too low or too high, and when you need to test for ketones. 
• Talk to your diabetes care team about ways to prevent health complications. You can take many steps to prevent or delay complications, such as losing weight, stopping smoking, and getting regular eye, dental, and foot exams. 

Who is at risk, and when to see a doctor

People with diabetes sometimes will have high blood sugar in the morning. This can be due to various causes, such as the dawn phenomenon, waning insulin, or the Somogyi effect. Your diabetes care team can help you figure out what is causing your morning high blood sugar, and help find a solution to get you back in the normal range when you wake up.

In general, high blood sugar levels can have both short-term and long-term complications. People with Type 1 diabetes are at higher risk of diabetic ketoacidosis, or DKA, especially when blood sugar increases above 240 to 300 mg/dl. People with Type 2 diabetes are at greater risk for diabetic hyperosmolar hyperglycemic syndrome (HHS), which can occur with very high blood sugar levels, sometimes over 600 mg/dl. DKA and HHS are life-threatening and can lead to comas or death if untreated, so people with diabetes should learn what symptoms to be alert to and get emergency medical help when needed.

Having high blood sugar over long periods of time can cause many complications, including problems with the eyes, feet, nerves, heart, and kidneys. This is why it is essential to identify the causes of high blood sugar, and focus on keeping blood sugar within the target range as much as possible. People with diabetes should keep in regular contact with their diabetes care team, reporting numbers or sharing CGM data regularly. And always consult the healthcare provider with any questions or concerns about high—or low—blood sugar.