High Blood Glucose Levels Before Breakfast

Diabetes is a disease that results from the body’s inability to control blood glucose (sugar) levels. In a person without diabetes, an organ called the pancreas secretes enough insulin to keep blood sugar levels from getting too high.

Insulin is a hormone that allows sugar in the bloodstream to enter cells, where it’s used as energy to carry out specific functions. Diabetes results when the pancreas either doesn’t make enough insulin or it doesn’t respond to insulin the way it should.

There are two main ways we attain blood sugar: through eating and from the liver. When we eat food, especially carbohydrates such as bread and fruit, it turns into blood sugar after being digested. The other way blood sugar levels rise is when the liver releases some of its stored sugar called glycogen. The liver stores sugar to help ensure blood sugar levels don’t fall too low, such as during fasting or intense exercise.

In a functioning pancreas, there is a small and consistent amount of insulin being released; this is called basal insulin. When food is consumed, and blood sugar levels rise, the pancreas releases a larger amount of insulin to help offset the rise in blood sugar; this is called bolus insulin. When people inject insulin for diabetes, they usually inject a combination of basal and/or bolus insulins to mimic the pancreas’ natural function.

Monitoring blood sugar levels is an important part of managing diabetes. People with diabetes may check their blood sugar anywhere from once daily to over six times a day, depending on the circumstances. The most common time to check blood sugars is in the morning after waking and before eating; this is called fasting blood sugar. When blood sugar levels are high in the morning, it can be an indicator that something needs to change in the diabetes care plan to improve blood sugar control and reduce the risk of diabetes complications.

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Why is blood sugar high in the morning?

According to the American Diabetes Association, fasting blood sugar should be between 70-130 mg/dL, while the American College of Endocrinologists recommends a fasting blood sugar below 110 mg/dL. If blood sugar is higher than this range, it could be due to several different causes.

Insulin resistance: One of the most common causes of type 2 diabetes is insulin resistance. Insulin resistance occurs when the cells don’t respond well to insulin, causing the pancreas to release more insulin to try to compensate. Over time, this can cause the pancreas to lose some of its functioning and lead to insulin deficiency. 

Some of the possible symptoms of insulin resistance include:

  • Waistline over 40 inches in men and 35 inches in women

  • Blood pressure 130/80 or higher

  • Fasting glucose over 100 mg/dL

  • Fasting triglycerides over 150 mg/dL

  • HDL (“good”) cholesterol under 40 mg/dL in men and 50 mg/dL in women

  • Skin tags

  • Patches of dark, velvety skin called acanthosis nigricans

Certain genetic and lifestyle factors are associated with insulin resistance. Some of these risk factors include:

  • Obesity (having a body mass index of 30 or greater)

  • Sedentary lifestyle

  • Diet high in carbohydrates, especially added sugars

  • Gestational diabetes (diabetes during pregnancy)

  • Nonalcoholic fatty liver disease and polycystic ovary syndrome (PCOS)

  • Family history of diabetes

  • Smoking

  • Being of African, Latino, or Native American descent 

  • Being age 45 or older

  • Hormonal disorders like Cushing’s syndrome and acromegaly

  • Medication use, especially steroids, certain antipsychotics, and HIV medications

  • Sleep apnea

Not enough insulin. In people who take insulin for diabetes, such as those with type 1 diabetes, high blood sugar in the morning before breakfast is likely a sign that they aren’t receiving enough basal insulin. It can also be a sign that the dosages of other types of diabetes medications need to be increased. 

Rebound hyperglycemia. If blood sugar levels fall too low during sleep, the liver can release sugar to help counteract the low blood sugar (hypoglycemia). If too much sugar is released and the low blood sugar is over-corrected, high blood sugar before breakfast can be the result.

Eating habits. The most simple explanation for high blood sugar before breakfast is if someone eats later than usual or eats a carbohydrate-heavy meal or snack right before bed. Fasting blood sugar is usually defined as not having had anything to eat or drink (besides water) for 8-12 hours, so if blood sugar is tested sooner than that, it’s not truly considered fasting.

The Dawn Phenomenon

The Dawn Phenomenon is a term for high blood sugar in the early morning hours, usually between 2 and 8 AM, in people with diabetes. This usually occurs due to the release of counterregulatory hormones during sleep.

Counterregulatory hormones are those that act against insulin, meaning they raise blood sugar. Hormones such as human growth hormone, cortisol, glucagon, and epinephrine cause insulin resistance and raise blood sugars.

One of the best ways to determine if someone is experiencing the Dawn Phenomenon is to set an alarm and check blood sugars early in the morning, around 2 or 3 AM. If they are high, then it’s likely due to the Dawn Phenomenon. In general, high blood sugar is considered anything over 180 mg/dL, but this will vary depending on the person’s blood sugar targets.

The Somogyi Effect

The Somogyi effect occurs when someone takes insulin before bed and experiences high blood sugar levels in the morning, and it tends to happen more in people who have type 1 diabetes.

It occurs when too much insulin is taken or if blood sugar levels fall too low during the night. The body’s response to the lower blood sugar is to release more stored sugar from the liver, which is called glycogenolysis, as well as releasing counterregulatory hormones that oppose insulin, therefore raising blood sugar.

The main difference between the Dawn Phenomenon and the Somogyi effect is that the Somogyi effect is due to low blood sugar, whereas the Dawn Phenomenon isn’t.


Testing blood sugar in the morning before breakfast is the only way to know if it’s running high. It’s best to check blood sugar shortly after waking but before eating to get an accurate picture of the fasting blood sugar level. 

To determine why blood sugar is high before breakfast, it may require testing in the middle of the night (around 2-3 AM) to better identify whether the Dawn Phenomenon or the Somogyi effect is to blame.

Another good test to have done regularly is the hemoglobin A1c. The hemoglobin A1c measures the average blood sugar over the past 90 days, giving a bigger picture of blood sugar control. The American Diabetes Association recommends a goal of less than 7% for people with diabetes, while the American Association of Clinical Endocrinologists recommends an A1c of 6.5% or lower.


Treatment of high blood sugar before breakfast will depend on the causes. If it’s due to insufficient insulin or other diabetes medication, the medication regimen should be reviewed with the person’s healthcare provider. For someone taking insulin, high blood sugar in the morning usually means that the basal insulin dose needs to be increased.

For someone not taking medication for their diabetes, lifestyle changes may be enough to lower blood sugar before breakfast. Some of the ways to help promote ideal fasting blood sugar levels include:

  • Eating a consistent carbohydrate diet. Carbohydrates have the biggest impact on blood sugar levels. People with diabetes don’t necessarily need to follow a very low carbohydrate diet, but keeping their carbohydrate intake consistent throughout the day can help prevent blood sugar spikes. Some people prefer to count carbohydrates to help keep their blood sugar on track. In general, 30-60 grams of carbohydrates per meal and 15-30 grams of carbohydrates per snack are used as goals. Still, someone’s ideal carbohydrate intake will vary due to many factors such as physical activity level and blood sugar trends.

  • Stay physically active. Getting 30 minutes of moderate to vigorous activity most days of the week for a goal of at least 150 minutes per week is ideal. Exercise helps the body use up glucose and reduces insulin resistance, promoting lower blood sugar levels for hours after exercise is completed.

  • Practice good sleep hygiene. Poor sleeping habits and shift work have been associated with increased blood sugar levels. Lack of sleep or a disrupted circadian rhythm seems to interfere with the body’s insulin response, leading to insulin resistance. The National Sleep Foundation also recommends several things to improve sleep hygiene, such as:
  • Limiting daytime naps

  • Avoiding caffeine and other stimulants close to bedtime

  • Exercising during the day

  • Avoiding heavy, fatty, or spicy foods close to bedtime

  • Being exposed to natural light during the day

  • Establishing a relaxing bedtime routine

  • Keeping the sleeping environment comfortable, e.g., temperature between 60-67 degrees, using white noise machines, etc.


If blood sugar levels are high before breakfast, they’re likely high during the day and after eating as well. Consistent high blood sugar does damage to the arteries and vessels of the body, especially when people have diabetes for a long time. When these vessels are damaged, complications can occur. Some of the complications from chronic high blood sugar include:

  • Heart (cardiovascular) disease: people with diabetes are two to four times more likely to die from cardiovascular disease than those without diabetes. People with diabetes are also more likely to have high blood pressure, which is another risk factor for heart disease. A heart attack is one potential complication of heart disease.

  • Stroke: Diabetes increases the risk of stroke, as well as increases mortality when a stroke occurs.

  • Kidney disease and failure: High blood sugar damages the kidneys and can lead to kidney disease. About one in four people with diabetes have kidney disease.

  • Poor wound healing leading to amputations: High blood sugar inhibits proper wound healing. Diabetes is thought to be the leading cause of leg amputations worldwide.

  • Neuropathy: Damage to the nerves, which can cause painful symptoms like numb and tingling legs and feet, as well as delayed stomach emptying from damage to the nerves of the stomach.

  • Retinopathy and blindness: Damage to the nerves in the eyes is called retinopathy, which can lead to blindness if not treated.


Blood sugar levels should be between 70-130 mg/dL before breakfast. This number is often referred to as fasting blood sugar since it’s measured after a night of sleep and before eating. High blood sugar levels before breakfast are a sign that blood sugar targets aren’t being met. 

Some potential causes of high blood sugar before breakfast include insulin resistance, the Dawn Phenomenon, the Somogyi effect, eating a large amount of carbohydrates before bed, eating late, and inadequate insulin or other medication dosages. 

Taking medications as prescribed and changing medication dosages as needed, eating a consistent carbohydrate diet, staying physically active, and practicing good sleep hygiene can help promote healthy blood sugar levels, reducing the risk of long-term diabetes complications. 

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  1. https://www.sleepfoundation.org/articles/sleep-hygiene
  2. https://www.ajmc.com/newsroom/diabetic-amputations-may-be-rising-in-the-united-states
  3. https://www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/heart-disease-stroke
  4. Chen R, Ovbiagele B, Feng W. Diabetes and Stroke: Epidemiology, Pathophysiology, Pharmaceuticals and Outcomes. Am J Med Sci. 2016;351(4):380-386. doi:10.1016/j.amjms.2016.01.011

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