If you’re waking up with high blood sugar—even after eating well the night before—you’re not alone. Morning highs are a common frustration for people with diabetes. Let’s break down why they happen and what you can do to get back in range.

Common Causes of High Morning Blood Sugar

🌅 1. Dawn Phenomenon

This is the most common reason. Between 3–6 a.m., your body naturally releases hormones (like cortisol and growth hormone) that prepare you to wake up. These hormones make your liver release extra glucose into your blood. If your insulin isn’t enough to match it, your blood sugar goes up.

• You go to bed with a normal blood sugar
• You don’t go low overnight
• Your glucose gradually rises around 3–6 a.m.

🌙 2. Somogyi Effect (Rebound Highs)

This happens when your blood sugar drops too low overnight, and your body “rebounds” by releasing hormones that push it too high.

Signs it’s the Somogyi effect:

• You wake up high after going low in the middle of the night
• You may feel sweaty, shaky, or have bad dreams
• CGM or a 2–3 a.m. check shows a low

🍔 3. Late-Night Eating or Snacking

If you eat a large meal or a carb-heavy snack right before bed—especially without enough insulin or medication—it may lead to elevated glucose in the morning.

💉 4. Too Little Long-Acting Insulin

If you’re using basal insulin, a dose that’s too low may not last through the night, letting glucose rise as you sleep.

How to Troubleshoot High Morning Glucose

1. Check your glucose around 2–3 a.m.
   • If it’s low: You may be having a rebound (Somogyi)
   • If it’s rising gradually: It may be dawn phenomenon
   • If it’s high all night: It could be food, missed meds, or not enough insulin
2. Look at your evening habits:
   • What time do you eat dinner or snacks?
   • Did you take your meds or insulin at the right time?
   • Did you drink alcohol before bed?
   • Did you have physical activity (or skip it) in the evening?
3. Talk to your care team:
   • You might need to adjust your insulin timing or dose
   • You may benefit from a small bedtime snack with protein and fat if lows are causing rebounds
   • CGM data can help pinpoint the pattern

Takeaways

Morning highs can be managed once you know the cause. Use your CGM (or check manually) at 2–3 a.m. to help uncover the pattern.

With the right adjustments, you can wake up in range and feel more in control. Always talk to your care team to double check your suspicions before taking action.