Why are my blood sugars affected by my period?

Ask our CDE

Why are my blood sugars affected by my period?


Dear CDE,

Every month when I have my period I experience fluctuations in my blood sugar levels.  Why does this occur?  I've asked my other "DiabetesSisters" if this happens to them as well.  For some, it doesn't but for others, it does.  Some of my friends have high blood sugars a few days before their period starts (like me) while my other female friends' blood sugars go low!!  What gives??


Dear Reader,

Unfortunately, there have been very few studies in the area of menstruation and blood sugar control.  The common finding is that menstruation’s affect on blood sugar control is varied depending on the individual.  As a result, blood sugar testing during this time is the only way to know how it affects that particular woman’s blood sugar.

One study by Villanova University College of Nursing revealed decreased insulin sensitivity during menstruation being the most common issue.  This decreased insulin sensitivity means that the insulin that patients were taking or the pancreas was producing were not sufficient to lower blood sugar, resulting in hyperglycemia or high blood sugar.  According to studies and reports, this decreased insulin sensitivity  could be related to hormone fluctuations during different phases of the menstrual cycle or from symptoms of Premenstrual Syndrome (PMS) such as bloating, cramps, and mood swings.  During menstruation estrogen and progesterone are at their lower levels.  These are hormones that are produced by the ovaries in reaction to stimulation of Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH) all needed in normal menstruation.  Estrogen and Progesterone are at their peak in the premenstrual phase.  This is where they stimulate the endometrium to prepare a thick layer of blood vessels that will support a fertilized egg should pregnancy occur.  Progesterone is thought to be the main culprit in decreased insulin sensitivity.  This thought does not have much in the form of explanation.

In some cases DKA can occur with fluctuations.  Some feel that insulin sensitivity during menstruation is similar to the dawn phenomenon, in which all people with diabetes do not experience it.  Dawn phenomenon is when someone with diabetes has very high blood sugar (hyperglycemia) in the early morning due to the release of certain hormones.  These hormones are called counterreulatory hormones and they work against the action of insulin.  The hormones glucagon, epinephrine, growth hormone, and cortisol all increase blood sugar when needed by stimulating the liver to release glucose and inhibiting glucose utilization.

H.I. Cramer was the first researcher to notice fluctuations in blood sugar due to menstruation.  His findings were published in the Canadian Medical Association Journal in 1942.  He found that 38% of the women reported that menstruation had changed their diabetes control.  70% of those women reported deterioration of control by experiencing hyperglycemia.  30% experienced hypoglycemia and improved control. 
Studies also show increased insulin sensitivity or no affect in women as well.  Mechanisms for changes in blood sugar control continue to be undermined.  It is very difficult to document as there are other factors affecting insulin sensitivity.  Also, women in the age range for menstruation are very busy and hard to recruit for further studies (I know you all are smiling right now as you know this to be true!).

Some feel with increasing technology in diabetes, such as Continuous Glucose Monitoring (CGM) will be able to make it easier for women to identify patterns and make decisions on how to improve control during menstruation.  The best thing is to test blood sugar frequently during premenstrual syndrome and menstruation and determine individual needs.