Dawn phenomenon

by Jim Hartmann

One of the most frustrating things that diabetics deal with is an unexpected rise in blood glucose overnight. You go to bed with a BG of 100 mg/dL (5.6 mmol/L), and wake up with a BG of 130 (7.2)! You didn’t eat, so what happened?

This results from two distinctly different processes: Dawn Phenomenon and Somogyi Effect. Here are some basics.


Everyone, diabetic or not, exhibits some Dawn Phenomenon. It is a natural part of our bodies’ circadian rhythms. Some have said it is the way our ancestors had the strength to rise and slay a woolly behemoth for breakfast.

Since most of us fast while sleeping, with teenagers a possible exception, our bodies use stored energy during sleep. The body uses all three macro-nutrients (carbohydrates, proteins, and fats) to store energy.

The most easily used is the storage medium of carbohydrates, called glycogen. Glycogen is made from glucose, and is stored in the liver and muscles. Since it is basically nothing more than a complex matrix of glucose, it is easy for the body to store and use, something the body does all day long. The technical term for the act of creating and storing glycogen is glycogenesis. When the body calls for the conversion of glycogen back to glucose it is called glycogenolysis.

Another macro-nutrient that is available to be converted to glucose is protein. Most of us think of our protein as being stored in muscle, but the body has protective mechanisms to make muscle wasting its last choice. One of the most useful and readily available sources of protein storage is in blood components, i.e., albumin (plasma). The body uses a process performed in the liver to convert amino acids, the building blocks of proteins, into glucose. The name for this process is gluconeogenesis, literally “the creation of new glucose”.

So, what does all this have to do with a high fasting BG? Overnight, usually between 4am and 11am, your body releases some hormones. These are Growth Hormone (GH) from the anterior pituitary gland, cortisol from the adrenal cortex, glucagon from your pancreatic alpha-cells, and epinephrine (adrenalin). These hormones cause an increase in insulin resistance, raising your BG. In addition, these hormones trigger glycogenolysis and gluconeogenesis, adding stored or new glucose to your bloodstream.

Dawn Phenomenon, and its associated increase in insulin resistance, is the reason most diabetics are far more sensitive to carbs in the morning.

Dealing with Dawn Phenomenon

There are many ways of defeating Dawn Phenomenon. You will have to experiment with the following suggestions to see what works for you.

  1. Try eating no food after dinner. This works for people whose Dawn Phenomenon isn’t very strong. Basically, it lowers their baseline BG, so that when DP does hit them, the increase keeps them below a certain level, usually 120 (6.7).
  2. Try eating a small snack of fat and protein before bed. Most find that a tablespoon of peanut butter, or some cheese and deli meat are effective. The theory here is that the slow-digesting fat and protein holds their BG high enough overnight to avoid Somogyi Effect (see below).
  3. Eventually, you will learn how the two disparate approaches above work for you. Hopefully, you will set personal targets to guide you, eg., if my BG is below XXX (insert your target here), I need a snack. If my BG is over XXX, I don’t need a snack.
  4. The prescription medication Metformin HCl (Glucophage) is often very effective in limiting Dawn Phenomenon for Type-2s and insulin resistant Type-1s. Of course, Type-1s can adjust their basal (slow) insulin regimen to account for Dawn Phenomenon.
  5. Lastly, EAT BREAKFAST. The resulting increase in blood glucose from food will often turn off the continued rise. If you don’t, some diabetics will continue to rise until 10-11 am.


Somogyi Effect, named for Dr. Robert Somogyi, its discoverer, is a high morning BG due to a low overnight. It is most commonly seen with insulin using diabetics, but is also seen with overnight reactive hypoglycemics.

The mechanism is a low overnight, which causes the body to react by releasing many of the same hormones seen in DP. The strongest blood glucose increasing hormone, glucagon, plays an important role. It tells your liver to start glycogenolysis and gluconeogenesis to provide enough glucose for your body to survive. This is sometimes referred to as a Liver Dump. Often, this mechanism over-produces, and you wake to a significantly higher BG.

Setting your bedtime BG target a bit higher, will usually prevent you from having a hypoglycemic event overnight.

Editor’s Note:

This article is taken from Jim Hartmann’s site: www.diabetic-talk.org

Jim helped a lot of diabetics until his death in early 2009. This is an article which we refer to frequently and we are not sure whether that site will continue without Jim. We are unable to contact the copyright holder so if there are any objections to the use of this article, please email admin@diabetes-support.org.uk