You may have high blood sugar in the morning for several reasons, such as the waning action of insulin medications or the “dawn effect.”

Chronically high blood sugar levels can damage many tissues in your body and are responsible for many of the complications of diabetes. Most people’s blood sugar levels are lowest in the morning after waking and peak several times throughout the day shortly after eating.

Some people may notice that their blood sugar levels are higher than expected when they wake up. This increase is often due to a phenomenon called the dawn effect, which is caused by a surge of anti-insulin hormones in the early morning.

Let’s examine some of the reasons why your blood sugar levels may be high in the morning.

High blood sugar is often silent, meaning it doesn’t cause any noticeable symptoms, but it can damage tissues in your body over time. Very high blood sugar can cause some noticeable symptoms, such as:

According to the American Diabetes Association, the main causes of high blood sugar in the morning are the dawn phenomenon and waning insulin.

Dawn phenomenon

The dawn phenomenon is a natural increase in blood sugar levels in a person with diabetes in the early hours of the morning, often between 4 a.m. and 8 a.m.

Normally, your body produces a surge of extra insulin in the early morning to counteract the effect of other hormones with anti-insulin effects, such as growth hormone.

People with diabetes don’t produce enough insulin to counteract the effects of these hormones and experience a rise in their blood sugar levels.

Dropping insulin levels

If you’re taking insulin, its effect may wane by the time you wake up. As the concentration of insulin drops in your blood, your blood sugar levels increase through the night.

You may have waning insulin if your insulin pump provides too little insulin overnight or if your long-acting insulin dose is too low or injected too early in the day to last until the next morning.

Somogyi effect (Somogyi phenomenon)

The Somogyi effect is another phenomenon that causes high blood sugar. Unlike the dawn phenomenon, it’s thought to be a rebound effect from low blood sugar late the night before potentially due to the overproduction of hormones like adrenaline and growth hormone.

Recent studies dispute the Somogyi effect and have observed that most people with high early morning blood sugar also have high evening blood sugar.

Certain medications

Some medications can raise your blood sugar and may lead to hyperglycemia in the morning or another time of day. The main classes of drugs linked to hypoglycemia include:

  • glucocorticoids
  • HMG-coA reductase inhibitors
  • thiazide diuretics
  • beta-blockers
  • antipsychotics
  • fluoroquinolones
  • antiretrovirals
  • antineoplastic agents
  • immunosuppressants

Dietary or exercise changes

Changes to your dietary or exercise habits may contribute to hyperglycemia.

If you eat a high carbohydrate meal the night before, you might not have enough insulin to drop your blood sugar levels into a healthy range.

Changes in your exercise habits may also contribute to changes in your blood sugar levels. Aerobic exercise has a blood-sugar-lowering effect. Suddenly decreasing exercise levels in the evening may raise your blood sugar levels in the morning if you continue taking the same amount of insulin.

Sleep apnea

Research suggests that sleep apnea might induce insulin resistance and hyperglycemia.

According to the Centers for Disease Control and Prevention, typical times to test your blood sugar are:

  • when you first wake up before eating or drinking
  • before a meal
  • 2 hours after a meal
  • at bedtime

Your blood sugar levels increase after consuming carbohydrates, so the timing of your test can influence how your doctor interprets your measurements.

Your doctor may recommend frequent testing if you have:

Ways you may be able to improve blood sugar regulation/management in the morning include:

  • speaking with your doctor about adjusting your medication
  • increasing exercise in the evening
  • increasing protein to carbohydrate ratio in your evening meal
  • eating breakfast to decrease the secretion of hormones that act against insulin

Chronically high blood sugar can damage many tissues in your body and lead to complications, such as:

It’s a good idea to contact your doctor if you consistently see blood sugar readings above your target range, especially if you notice a sudden increase from your normal levels.

If you develop symptoms of high blood sugar, it’s important to take your medication attention since this may mean your blood sugar levels are dangerously high.

What should your blood sugar levels be in the morning?

The expected values for fasting blood glucose concentration are between 70 mg/dL (3.9 mmol/L) and 100 mg/dL (5.6 mmol/L).

What is the best time to check blood sugar in the morning?

It’s a good idea to check your blood sugar levels when you first wake up before you eat and drink anything.

What brings down blood sugar immediately?

Rapid-acting insulin is the quickest way to lower blood sugar. Learn more about the types of insulin.

High blood sugar in the morning is commonly caused by the dawn phenomenon in people with diabetes. The dawn phenomenon is when blood sugar levels rise due to inadequate insulin to counteract anti-insulin hormones. Insulin levels waning in your blood while you sleep may also contribute.

It’s a good idea to speak with your doctor if you’ve been experiencing frequent bouts of high blood sugar. They may recommend changing your medications or making changes to your lifestyle habits.