In the care of women with diabetes, we sometimes see that blood sugars vary with the menstrual cycle.  In particular, sugars can be higher in the week before the period starts. Why does this happen?


There is actually not a lot of data in this area to inform us.  In a study of healthy premenopausal women without diabetes, it was shown that insulin resistance is  higher in the second half of the menstrual cycle than the first half.  Insulin resistance is highest just after ovulation, then declines just before the period starts (but still higher than in the first part of the menstrual cycle).   This increase in insulin resistance in the second half of the cycle may be because progesterone (which is highest just after ovulation, then declines during the rest of the second half of the cycle) may antagonize the action of insulin in the fat cell (based on animal study).   When insulin resistance is higher, more insulin is needed to control blood sugars.  In a person without diabetes, the pancreas takes care of it by releasing more insulin.  In a person with diabetes, sugars will rise if insulin resistance goes up.


The days leading up to the period can also be uncomfortable and/or painful, and pain is also a known cause of increased blood sugars.


The above being said, there are some women who notice no difference in their blood sugars by time of month in their cycle.


So at the end of the day (well, the end of the month I suppose!) – diabetes management is always tailored to the individual.  For women who struggle with higher sugars in the days before their period, it may be helpful to build a ‘pre period’ treatment regimen that is different that the other weeks of the month, constructed in response to what her blood sugars have shown.


Thanks to my friend, pharmacist and Certified Diabetes Educator Supreme, Esmond Wong, for the question that led to this post!


Dr Sue Pedersen © 2019 

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