Very high blood glucose in the early morning due to the release of certain hormones in the middle of the night.

We often hear the question, “Why is it that my fasting blood glucose is always so much higher than at any other time of the day? Especially when I have had nothing to eat since supper (or bedtime)!”

The Diabetes Council (June 10, 2020) explains it like this: “The Dawn Phenomenon (also known as the Dawn Effect) was defined over 30 years ago in T1D [type 1 diabetes] as the elevation of blood sugars during the night and early morning hours and an even greater rise in blood sugar after breakfast…. The current definition of the Dawn Phenomenon is ‘the need for insulin to prevent the rise of blood sugar levels in the early morning hours of predawn and dawn…’. Anywhere from 10% to 50% of people with T2D [type 2 diabetes] and T1D [type 1 diabetes] experience the dawn phenomenon.”1

At its most simple, “Dawn Phenomenon” is “very high blood glucose in the early morning due to the release of certain hormones in the middle of the night.”

Dr. Jason Fung, author of The Diabetes Code, explains it thoroughly in an article (referenced in the Endnotes for this chapter) from which I have summarized the key points:

  • The “Dawn Phenomenon” occurs in both diabetics and non-diabetics. However, it’s barely noticed in non-diabetics who don’t have insulin resistance.
  • Your body’s blood sugar lowers during the night while you are sleeping. But around 4 a.m., your body senses your blood sugar is low and secretes hormones (cortisol, glucagon, and adrenaline) to counter the low blood sugar by raising blood sugar. This is to get the body ready for the day ahead.
  • The body also secretes insulin to counterbalance the higher blood sugars.
  • But in diabetics (or others who are insulin resistant), the increased insulin does not have the effect of lowering blood sugars. So the hormones are still working, and the blood sugar keeps rising.
  • Fung’s solution is “Simple. Either don’t put any sugar in (LCHF) or burn it off (fasting). Even better? LCHF (low-carb high-fat) + IF (Intermittent Fasting).”

The full article (referenced in the Endnotes for this chapter) contains Dr. Fung’s detailed explanation, with helpful illustrations, to describe Dawn Phenomenon. Dr. Fung concludes by saying, “The Dawn Phenomenon, or higher blood sugars during fasting, does not mean you are doing anything wrong. It’s a normal occurrence. It just means that you have more work to do…. By itself it is neither good nor bad. It is simply a marker that your body has too much sugar.”2

Other sources I consulted give the same basic information about “Dawn Phenomenon” and why it occurs. But they give a variety of other solutions, including:

  • Eat a protein/fat snack (such as nuts, cheese, protein smoothie, or hard-cooked egg) at bedtime. (This goes against our basic principle of no bedtime snacks!)
  • Eat a protein/fat snack within one hour of waking. (This doesn’t specify when, exactly, to test your fasting blood glucose.)
  • Change your exercise schedule to afternoon or evening since a morning exercise may elevate your blood glucose even more. (This is a valid point, confirmed by Dr. Richard K. Bernstein.)
  • Take apple cider vinegar (liquid or tablet form) at night and in the morning. Start with a small amount and gradually work up to a maximum of 2 tablespoons (30 ml) per day.
  • Make certain you are getting sufficient anti-oxidant vitamins (e.g., Vitamins C, E, and the beta-carotenes), B-complex vitamins, and minerals such as selenium, zinc, chromium, and boron.

For patients on medication and/or insulin, some sources recommend:

  • Talk to your doctor about a different medication and/or insulin type.
  • Ask your doctor for an insulin pump.

And finally, “The dawn phenomenon is not necessarily something that needs to be fixed. It’s important to keep in mind that even though your fasting glucose may be elevated, you may have lower or normal glucose values throughout the rest of the day. It’s not uncommon for patients reversing their diabetes through nutritional ketosis to experience the dawn phenomenon and still see improvements in their HbA1c. Why? Because HbA1c is a measure of your blood glucose over the last 3 months. The average value matters more than any individual blood glucose value.” –Brent Creighton, PhD3


1The Diabetes Council Team; reviewed by Dr. Sergii Vasyliuk, MD. “Why Is My Blood Glucose So High in the Morning? The Dawn Phenomenon,” The Diabetes Council (June 10, 2020). (accessed on 7/30/2020).

2Fung, Dr. Jason. “The Dawn Phenomenon – T2D 8,” The Fasting Method, n.d. (accessed on 7/30/2020).

3Mowll, Dr. Brian. “What Causes The Dawn Effect,” The Diabetes Coach Dr. Mowll (March 21, 2018). (accessed on 7/30/2020).

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Dr. Jason Fung, author of The Diabetes Code, explains it thoroughly in this article from which I have gleaned information and tried to summarize and provide excerpts from.

The Dawn Effect, sometimes also called the Dawn Phenomenon (DP) was first described about 30 years ago. It is estimated to occur in up to 75% of T2D patients although severity varies widely. It occurs both in those treated with insulin and those that are not. The circadian rhythm creates this DP.

Just before awakening (around 4am), the body secretes higher levels of Growth Hormone, cortisol, glucagon, and adrenalin. Together, these are called the counter-regulatory hormones. That is, they counter the blood sugar lowering effects of insulin, meaning that they raise blood sugars. The nocturnal surge of growth hormone is considered the primary cause of the DP.

These normal circadian hormonal increases prepare our bodies for the day ahead. That is, glucagon tells the liver to start pushing out some glucose. Adrenalin gives our bodies some energy. Growth hormone is involved in repair and new synthesis of protein. Cortisol, the stress hormone increases as a general activator. After all, we are never quite so relaxed as deep sleep. So these hormones gently get us ready to wake up. A good ol’ fashioned hormonal kick in the ass, so to speak. Hormones are secreted in a pulsatile manner peaking in the early morning hours then falling to low levels during the day.

Since these hormones all tend to raise blood sugars, we might expect that our sugars would go through the roof in the early morning. This does not actually happen.

Why? Insulin secretion also increases in the early morning to counteract the counter regulatory hormones. In other words, insulin is there to make sure blood sugars do not go too high. However, if you look closely at the blood sugar readings, there is a slight increase in the morning time.

So, in the normal, non-diabetic situation, blood sugars are not stable throughout 24 hours. The Dawn Effect happens in normal people. This is easily missed because the magnitude of the rise is very small – from 89 to 92 mg/dl. However, this effect was found in every patient studied. So, unless you are specifically looking for the DP, you are likely to miss it.

Think about it this way. Your body has the ability to store food energy as sugar (glycogen) and fat. When you eat, you store food energy. As you sleep (fasting), your body needs to release this stored energy. Around 4am or so, knowing that you will soon be waking up, your body prepares you for the upcoming day. It does this by increasing counter-regulatory hormones to release sugar into the blood. You can see that glucose production falls overnight and starts to ramp up around 4 am. In order to prevent the sugars from rising too much, insulin increases to act as a ‘brake’ on the system….

However, in T2D, the body has high insulin resistance, meaning that the insulin has minimal effect at lowering the blood sugars. Since the counter regulatory hormones (mostly growth hormone) still are working, blood sugars rise unopposed, and therefore much higher than the normal non diabetic situation….

Think about it this way. The Dawn Phenomenon is simply moving sugar from body stores (liver) into the blood. That’s it. If your body stores are filled to bursting, then you will expel as much of that sugar as possible. By itself it is neither good nor bad. It is simply a marker that your body has too much sugar. Solution? Simple. Either don’t put any sugar in (LCHF) or burn it off (Fasting). Even better? LCHF + IF.

You can read the complete article by Dr. Jason Fung at


What is the Dawn Phenomenon? [3:04]
Dr. Eric Berg

Additional References:

Controlling the Dawn Phenomenon

Controlling the Dawn Phenomenon

Diabetes? Don’t Let “Dawn Phenomenon” Raise Your Blood Sugar

Dawn Phenomenon

The Dawn Phenomenon

Why Is Blood Sugar Highest in the Morning?

Why Are Blood Sugars High in the Morning?

How Can I Prevent High Blood Glucose in the Mornings?