Why Am I Waking Up With High Blood Sugar?
Last updated: April 2023
It can feel like someone is just playing a cruel joke. I wake up in the morning to find that my glucose reading is high – higher than when I went to bed!
How can this be? My glucose level was in range last night at my bedtime check. All I did was sleep. Okay, maybe I got up in the middle of the night to pee. But shouldn't my reading have gone down overnight? Or at least stayed the same?
I'm experiencing the dawn phenomenon.
Why are glucose levels higher in the morning?
Sometime in the very early morning hours, our body starts releasing hormones as part of its regular wake-up routine. Without using a continuous glucose monitor, we can never be sure exactly when this happens. These hormones (cortisol and growth hormone, among them) trigger the liver to release glucose for energy and drive glucose levels up.1
The connection to insulin
With type 2 diabetes, the pancreas can't keep up with the need for insulin to bring those levels back down, so glucose levels look like they've gone up overnight. Unfortunately, in people with diabetes, the body either doesn't produce enough insulin in response or is insulin resistant and can't effectively use the insulin it does produce.2
Impact on A1C levels
If the dawn phenomenon happens occasionally, it's unlikely to have much of an effect on A1C. But if it becomes a regular thing, then it's time to make some changes to bring those morning readings back in range to prevent it from raising your A1C.3
What can be done to counter the dawn phenomenon?
A lot of what can be done in response to the dawn phenomenon looks like everyday diabetes management. It can take a little experimenting to figure out why you're experiencing the dawn phenomenon and how to respond.
If it seems like insulin resistance is behind the higher morning readings, exercise might help. Moderate exercise improves insulin resistance afterward. A short walk after dinner or in the morning can help decrease glucose levels.1,4
Regular moderate exercise can help improve insulin resistance overall. Examples include swimming, yoga, or 20 minutes on a stationary bike. After moderate exercise, the positive effect on insulin resistance lasts for hours. Make moderate exercise a regular thing, and the improvement remains in effect even during the days you don't exercise.1,4
Moderate exercise is what you want. Enough to get the blood flowing and the muscles moving, but nothing so vigorous that you get a burst of adrenaline. Hard exercise that gets the adrenaline flowing will cause a rise in glucose levels. This is how the body normally responds to adrenaline. The body will release energy in the form of glucose so that it can do the work that hard exercise demands.5
Adjusting eating habits
If morning readings are consistently higher after eating a higher-carb dinner, adjusting eating habits might be called for. Eating fewer carbs at dinner or when having a nighttime snack can help to lower overall glucose levels and keep the morning rise within range.1
Consult your healthcare provider
If exercise or changing eating habits don't bring morning readings back into range and you continue to experience the dawn phenomenon, it's probably time to talk with a healthcare provider about what else to do.
They might suggest other changes to your routine. Or they might, depending on what you're taking, want to make changes to your medication.
Changing insulin doses
Changing insulin doses either before dinner or at bedtime is a common response to the dawn phenomenon.1
However, changing insulin doses needs to be done with some care. Too high a dose of insulin can lead to hypoglycemia (dangerously low blood sugar) in the middle of the night.
Changes to medications
Your healthcare provider might suggest changing other (noninsulin) diabetes medications. Any medication that directly brings down glucose levels might be looked at as a way to counter the dawn phenomenon.1
Always talk with your healthcare provider before making any changes to how much or when you take your medications. Changing medication on your own can be dangerous. Without proper guidance, these changes can lead to hypoglycemia or other complications.
Waking up in range
Waking up refreshed and in range is how I like to start my day. Understanding what causes the dawn phenomenon helps me know how to respond and avoid being frustrated when it happens.
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