The menstrual cycle involves complex, dynamic fluctuations in sex hormones, particularly estradiol (estrogen) and progesterone, which can affect many different parts of the body, including glucose levels. People with type 1 diabetes can see changes in their glucose levels during this time for a few different reasons—below are some recommendations of how you can help manage it, along with some of the data we know about how the cycle can affect glucose levels.
Steps you can take to stay in range during menstrual fluctuations:
Proactively Address the Topic
Initiate conversations with your healthcare team about how the menstrual cycle or hormonal contraceptive use (e.g. challenges during the pill-free interval) can potentially impact your glucose and insulin patterns. Are you taking more insulin? Less? Are you stuck with “stubborn” highs?
Analyze for specific patterns
Using tools like CGM and insulin dosing/delivery profiles, menstrual cycle phase tracking (check out the different phases here), tracking apps or diaries, wearable devices (e.g., smartwatch, thermometer), and self-monitored hormone levels can help you compile data and understand patterns.
If you really want to dig into your patterns, take a look at your AGP report! Adjust the review period to match your cycle and look for certain patterns in that time frame (highs, lows, how insulin affects you post-meal, etc.). Work with your healthcare team to work through these patterns and make adjustments where needed.
Individualize your care to what works for you
Working with your healthcare team to adjust insulin timing and dosage can help you feel better, faster. Consider setting phase-specific carbohydrate-to-insulin ratios, insulin sensitivity factors, basal rate profiles, and bolus timing. For users of AID systems, adjust settings as appropriate—such as glucose targets and active insulin time (Medtronic 780G), or basal profiles and correction factors (IQ Control).
While these recommendations can help you feel more confident while managing menstrual cycle-related changes, we’re still learning exactly how these hormonal changes affect glucose levels. Here’s what we know so far:
Hormonal Dynamics:
Estradiol (estrogen) levels increase steadily during the late follicular phase (around day 8 to day 14 of your cycle), peaking sharply just before ovulation. Following a brief decline, levels rise again to a secondary, moderate peak during the mid-luteal phase (around day 15-28) before returning to baseline at the start of your period, or the early follicular phase. Progesterone levels remain low throughout the follicular phase but surge dramatically after ovulation, reaching a mid-luteal peak, followed by a rapid premenstrual decline.
How this affects your body:
These hormonal shifts influence key processes that affect glucose levels: insulin sensitivity, energy expenditure, gastric emptying, and appetite. Research on the isolated effects of estradiol indicates that it generally enhances insulin sensitivity, energy expenditure, and promotes fullness. However, we don’t completely understand how the effects of estradiol and progesterone fully affect the body, and in turn, glucose levels.
In addition to how it affects the bodily functions listed above, the menstrual cycle also influences systemic inflammation, with markers such as C-reactive protein (CRP) rising in the late luteal phase—which may further affect how the body breaks down glucose. Although the precise mechanisms remain unclear, the interplay of hormonal fluctuations, inflammatory signals, the autonomic nervous system and their downstream effects on physiology (e.g., insulin sensitivity, energy expenditure) and behavior (food intake, physical activity, sleep) contributes to variations in insulin demand. Simply put: there are a LOT of factors that affect your need for insulin during different times in your menstrual cycle.
Challenges in Type 1 Diabetes:
Evidence from studies, clinical practice, and reports from people with type 1 diabetes who menstruate consistently indicates that the menstrual cycle challenges diabetes management. High glucose levels before you start your period (when some experience PMS symptoms) are frequently reported, and the risk of diabetic ketoacidosis may be elevated during this phase. Data on low glucose levels are less consistent, with some studies suggesting increased risk during the early follicular phase (post-progesterone decline) or around the pre-ovulatory estradiol peak.
Everyone’s diabetes is different. Using time in range in your daily diabetes management can help you further understand how your cycle affects you, and can help you make the changes in your management routine that make you feel your very best—so that you can thrive with diabetes. Learn more about getting started with time in range here!