Different factors can affect blood glucose (sugar) levels in people with diabetes, such as physical activity, stress, illness, etc. and in the case of women, their menstrual cycle.
The menstrual cycle involves hormonal changes that can alter glucose levels and modify insulin needs. The hormones responsible for these changes are oestrogens and progesterone.
How do these hormones change throughout the cycle?
During the first half of each cycle, these hormone levels are relatively low, but in the second half, after ovulation, oestrogen and progesterone levels increase and then decrease drastically if there is no fertilization, producing what we know as a period or menstruation.
Why do changes in hormone levels affect blood glucose values?
Oestrogens generally make cells more sensitive to the action of insulin. Therefore, when the amount of oestrogens increases, blood sugar levels tend to decrease. Furthermore, progesterone induces insulin resistance, that is, it makes it more difficult for cells to use insulin, so when the concentration of progesterone increases, blood sugar levels also tend to rise. Therefore, women with diabetes can experience an increase in blood glucose levels the week before a period, right after ovulating, and show lower levels at the beginning of their period, although this pattern can vary among women.
Thus, if glucose levels are higher than normal before a period, you may need to increase your mealtime insulin dose (administered before each meal) or even your baseline insulin dose (which we normally call long-acting insulin), increase your exercise or modify your diet. Nevertheless, if glucose levels are lower than normal or you have hypoglycaemias, you should adjust your mealtime insulin dose or even your baseline insulin dose, by reducing it.
Two important aspects to help you regulate your glucose levels are monitoring your capillary blood glucose (if you use a glucometer) or interstitial glucose (if you use a sensor) and controlling your diet.
To know which are the effects of the different cycle phases on your glucose levels, you must increase the frequency of blood glucose logs so as to be able to establish patterns and repeating trends, especially the week before your period, so that you can adjust your insulin doses accordingly beforehand.
Furthermore, hormonal changes can make you feel hungrier and have cravings for certain foods, some of them particularly rich in carbs and fats, which can lead to a larger increase in glucose levels if you don’t control it appropriately: as well as adjusting your insulin dose, eating high-fibre foods that increase satiety can help you.
Dr Cintia González Blanco, Consultant 1 Endocrinology and Nutrition Service at Hospital de Sant Pau, Associate Professor at UAB and member of CIBER-BBN, Coordinator of the 2.0 diabetes group and member of the SED technologies applied to diabetes group; she is part of the editorial committee at SocialDiabetes.