Chit Chat for Diabetics

Why Blood Sugar Levels Rise in the Morning Before Eating

For many people living with diabetes or monitoring their health, one of the most puzzling experiences is waking up to find that blood sugar levels are higher than expected — even though they have not eaten since the night before. This phenomenon is common, and it is rooted in the body’s natural biology. Understanding why it happens requires a closer look at hormones, the liver, and the way the body prepares for the day ahead.

The Body’s Morning “Wake-Up” Response

When we sleep, our bodies are far from inactive. Behind the scenes, the brain and endocrine system are busy preparing us for the next day. As morning approaches, certain hormones are released — primarily cortisol, growth hormone, epinephrine (adrenaline), and glucagon. Together, these act like a biological alarm clock. Their job is to nudge the body into wakefulness by increasing alertness, raising heart rate, and most importantly, making glucose available for energy.

These hormones stimulate the liver to release glucose into the bloodstream, even if no food has been consumed. This ensures that the brain and muscles have the fuel they need to get moving in the morning. For people without diabetes, the body simultaneously produces insulin to keep this glucose release in balance. For those with insulin resistance or reduced insulin production, however, the balance is disrupted — leading to higher morning blood sugar readings.

The Dawn Phenomenon

This natural rise in blood sugar is often referred to as the “dawn phenomenon.” It typically occurs between 2:00 a.m. and 8:00 a.m. During these hours, the liver ramps up glucose production in response to those early-morning hormones.

In someone with healthy insulin function, the pancreas releases enough insulin to counter this rise, keeping blood sugar stable. But in people with type 2 diabetes or type 1 diabetes, the pancreas either does not produce enough insulin or the body’s cells do not respond properly to it. The result: fasting blood sugar levels appear higher in the morning, even though no food has been eaten.

The Somogyi Effect: A Different Mechanism

Another possible explanation for unexpected morning highs is the Somogyi effect, also called rebound hyperglycemia. This occurs when blood sugar drops too low overnight, often due to medication or insulin taken before bed. In response, the body releases stress hormones such as glucagon and adrenaline to raise blood sugar back up. Unfortunately, the rebound can overshoot, causing higher-than-normal readings upon waking.

The key difference between the dawn phenomenon and the Somogyi effect is the trigger:

• Dawn phenomenon = blood sugar rises naturally due to hormone surges.

• Somogyi effect = blood sugar rises as a rebound from overnight hypoglycemia.

Distinguishing between the two often requires overnight monitoring or continuous glucose tracking.

The Liver’s Central Role

The liver is the body’s glucose warehouse. When food is scarce, it releases stored glucose (glycogen) to maintain stable blood sugar levels. This process, called gluconeogenesis, ensures survival during fasting. Morning hormone surges specifically tell the liver to produce and release glucose. For people with insulin resistance, the liver tends to release more sugar than the body can handle, compounding the morning spike.

Why It Matters

Morning blood sugar spikes can be frustrating because they occur despite healthy evening habits. They also matter because prolonged high fasting glucose contributes to long-term complications of diabetes, including cardiovascular disease, kidney problems, and nerve damage. Understanding the cause allows individuals and healthcare providers to develop strategies to manage it.

Managing Morning Blood Sugar Rises

While morning glucose increases cannot always be eliminated, they can often be reduced or controlled through tailored approaches:

1. Medication Timing and Type – Adjusting when insulin or other medications are taken may help smooth overnight glucose levels.

2. Evening Snacks – For some, a small balanced snack before bed prevents overnight lows that could trigger rebound highs.

3. Physical Activity – Regular exercise improves insulin sensitivity, helping the body use glucose more effectively.

4. Monitoring Trends – Continuous glucose monitoring (CGM) or checking blood sugar at different points overnight can reveal whether the rise is dawn phenomenon or Somogyi effect.

5. Stress and Sleep Management – Since cortisol is a stress hormone, poor sleep or chronic stress can worsen morning highs.

The Bigger Picture

In short, morning blood sugar spikes are not mysterious, but rather part of the body’s normal rhythm. For those without diabetes, the body self-corrects. For people managing diabetes, however, the balance is disrupted — so the natural morning hormone surge can appear as an unwanted fasting glucose rise.

Recognizing that these increases are not due to “doing something wrong” but rather due to physiology is empowering. With monitoring, medical guidance, and lifestyle adjustments, morning blood sugar can be managed effectively.