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Dawn Phenomenon

Updated: Mar 18, 2020

First of all, look how cute my nephew is! This is us at the pool this weekend. Being an Aunty to this little guy is seriously one of the best things that has ever happened to me…okay, now onto our topic.


“A high morning reading ruins my whole day!” I hear this quite often! Early morning highs are difficult and often require multiple correction boluses. These AM highs are the result of a normal increase in the production of growth hormone, cortisol, and epinephrine; usually around 2am. We call this “dawn phenomenon”. In non-diabetics, insulin production is simply increased, however in PWD, this is not possible. The result is an increase in the production of glucose by the liver…hence, the rise in blood glucose levels.

When on an insulin pump, basal rates can simply be increased overnight, preventing dawn phenomenon. If a pump is not available however, things can get much more complicated… let me try to explain…There are many basal insulins currently available; Levemir, Lantus, Basaglar (generic of Lantus), Tresiba, and Toujeo. To best understand how to fend off dawn phenomenon, we need to understand the mechanism of action of each.

Levemir, Lantus, and Basaglar are made up of different components, but act very similarly. All can be taken between 1-2x/day. Levemir begins working within 1 hr, peaks in 5hrs, and has a duration of 18-24hrs. Lantus and Basaglar begin working in 1-2hrs, peak at 6hrs (less peak than Levemir), and have a duration of 18-24 hrs.

These three insulins when given at the correct time, will counteract “dawn phenomenon” with their peaks. But remember, a large nighttime dose can make it difficult to time this while still preventing nocturnal hypoglycemia before the peak. A peak of your insulin at 12am, for instance, may be the cause of your nighttime lows. Also keep in mind, not everyone has a “dawn phenomenon”.

Additionally; Lantus, Basaglar, and Levemir can be split into two doses if they are not lasting a full 24hrs (this is very common). For instance, Lantus given at bedtime may lose its efficacy around dinner the next day. The prandial (mealtime) insulin given for dinner will work for 4-5hrs after that but since Lantus takes 1-2hrs to kick in, there would be a gap in coverage leading to elevated morning glucose levels. This phenomenon is often misinterpreted as “dawn phenomenon”. People who experience this should try splitting their doses (with your clinician’s approval, of course).

The newest basal insulins available include Toujeo and Tresiba, both of which require 1 injection/day and have no true peak. This leads to very stable blood glucose levels, but cannot be timed to fight “dawn phenomenon”. Toujeo begins working after 6hrs and has a duration of 24-36hrs. Tresiba begins working after 1hr and has a duration of >42hrs. Because of this, Tresiba can be injected at different times of the day (>8hrs from previous dose) and eliminates the “gap” problem that I mentioned above. Tresiba is therefore great for people with hectic schedules or who sometimes miss their dosages.

I’ve been getting a lot of DMs about this, so I hope I helped answer some questions.

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