What Do We Know About the Dawn Phenomenon and Type 1 Diabetes?

The blood sugar increase that people with type 1 diabetes experience in the morning’s early hours is called the “dawn phenomenon.” This increase is caused by various hormones, like cortisol, that boost production of sugar by the liver.  

A common occurrence

A recent Canadian study measured the frequency and impact of this phenomenon among people living with type 1 diabetes. About half of the study’s participants experienced a significant increase in their blood sugar levels that generally started at around 3 a.m. 

The study also showed that the impacts of this phenomenon vary considerably from one day to the next and can increase insulin needs by 50%—as compared to insulin needs at the beginning of the night—from the second half of the night until the person wakes up.

Adjusting insulin doses 

People who experience the dawn phenomenon and inject long-acting insulin with a pen or syringe might find it very difficult to adjust their insulin doses accordingly. 

The insulin pump is often the best solution to consider, since it allows the user to adjust their insulin doses based on specific time slots. It’s then possible to program a higher dose for this time of night.

But the study also showed that adjusting nighttime insulin doses can be difficult due to several factors that affect blood sugar, e.g., type of insulin used, physical activity, hypoglycemia, bedtime snack, alcohol consumption, use of other medications, etc. 

Using a continuous glucose monitoring (CGM) system could help you identify this phenomenon and adjust your insulin dosage more easily.

The BETTER registry aims to better define the challenges facing people with type 1 diabetes in order to find solutions and improve access to treatments and technologies that help achieve better blood sugar management.

Register at www.type1better.com


  • Ostrovski, Ilia et al. (2019). Analysis of Prevalence, Magnitude and Timing of the Dawn Phenomenon in Type 1 Diabetes: Descriptive Analysis of 2 Insulin Pump Trials. Canadian Journal of Diabetes 42(5).

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