Dawn Phenomenon

Dawn phenomenon is the term given to an increase in blood sugar in the morning caused by the body’s release of certain hormones.  It is a relatively common phenomenon amongst Type 1 Diabetics.

Although often confused, Dawn Phenomenon is different from Chronic Somogyi Rebound, because it is not brought on by nocturnal hypoglycemia.

How is dawn phenomenon caused?

Dawn effect occurs when hormones (including cortisol, glucagon, epinephrine) are released by the body, causing the liver to release glucose.

The dawn effect therefore describes abnormally high early morning increases in blood glucose:

  • Usually abnormally high blood glucose levels occur between 8 and 10 hours after going to sleep for people with diabetes

woman sleeping

Why does the dawn phenomenon occur?

Researchers think that the release of the above-mentioned hormones may give rise to a brief period of insulin resistance which would also explain a rise in blood glucose levels.

It is thought that the body releases hormones that either impair the action of insulin or cause the liver to release extra sugar into the blood. This rise in blood glucose typically occurs around the time of waking.

Dawn phenomenon seems to affect some people but not others. There are theories as to why some people may be affected and not others but it’s not yet so well understood.

If you have high blood sugar it may or may not be a result of dawn phenomenon. If you are puzzled as to why you have high blood sugars in the morning, you may wish to wake and do a blood test in the night.

If your level during the night is significantly lower than your waking blood test result, then dawn phenomenon is likely.




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