Menstuation can affect your blood glucose levels because when two hormones – oestrogen and progesterone – are at their highest level just before your period, they affect insulin, which may cause blood glucose levels to rise.
Some women find their blood glucose rises considerably, while others do not notice a difference. In others, blood-glucose levels are lower before and during their periods.
You need to discover your own pattern so you can adjust your insulin accordingly. Often it is the fasting blood glucose before breakfast that tends to fluctuate the most. Being physically active in the week before your period, can help control fluctuations in your blood glucose levels.