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Premenstrual syndrome (PMS) is a common part of the menstrual cycle for many women. It’s a hormone-driven phase that can quietly affect how the body regulates blood sugar.
In the days leading up to a period, some people notice shifts in their glucose patterns. Responses vary widely from person to person and even cycle to cycle. Postprandial glucose may be slightly higher or take longer to return to baseline, whereas overnight glucose is less predictable. Others may notice little or no change.
This article examines the close relationship between hormones and glucose variability, why these shifts occur, and how using a continuous glucose monitor (CGM) can help reveal patterns so you can better understand your physiology.
What Is PMS and Why Hormones Matter
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Premenstrual syndrome (PMS) refers to a group of physical and emotional changes that can occur in the days leading up to a period. It occurs during the late luteal phase of the menstrual cycle and may be accompanied by symptoms such as bloating, cramps, breast tenderness, fatigue, and mood changes.
For some women, PMS symptoms are mild. For others, it can significantly affect daily routines, energy levels, and overall quality of life.
The menstrual cycle is broken up into phases:
- Follicular phase: Begins on the first day of your period and lasts until ovulation. During this phase, the body prepares for ovulation as estrogen and follicle-stimulating hormone (FSH) gradually rise after menstruation.
- Ovulation: Occurs mid-cycle. Just before ovulation, estrogen and luteinizing hormone (LH) peak and then decline, triggering the release of an egg.
- Luteal phase: Starts after ovulation and lasts until your next period begins. Progesterone rises as the body prepares for a potential pregnancy, while estrogen increases slightly before both hormones fall. These hormonal shifts contribute to PMS-related changes and ultimately trigger menstruation.
While estrogen and progesterone are best known for regulating reproduction, they can also influence insulin sensitivity and glucose metabolism.
These hormonal changes throughout the menstrual cycle are normal. Not everyone experiences PMS symptoms or changes in glucose variability, and when changes do occur, they are typically temporary. As the cycle returns to the follicular phase, hormone levels reset, and glucose patterns often follow suit.
What Is Glucose Variability?
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Glucose variability refers to the pattern your blood glucose follows over time, including how often it rises, how high it goes, and how smoothly it comes back down.
Throughout the day, blood glucose levels naturally rise and fall. Eating, physical activity, sleep, stress, and hormones can all affect glucose levels. Ideally, glucose levels rise gradually, but sometimes the pattern resembles sharp peaks with rapid drops.
When the body metabolizes carbohydrates effectively, glucose increases after a meal but returns to baseline efficiently. When glucose fluctuations occur more frequently, take longer to return to baseline, or spike higher, it may indicate that the body is less able to respond appropriately.
PMS Glucose Variability: The Influence of Hormones
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Fluctuations in hormones like estrogen and progesterone may influence how the body responds to glucose. For some individuals, this helps explain why glucose changes during PMS can vary rather than remain constant.2
How Estrogen and Progesterone Impact Blood Glucose
Estrogen and progesterone both interact with insulin signaling, but they can move it in different directions.
Estrogen is generally associated with:2
- Improved insulin sensitivity
- More efficient glucose uptake into the muscle
- Lower glucose output from the liver
The drop in estrogen during menopause helps explain the increase in insulin resistance for women as they get older.
Progesterone is linked to:2
- Impaired insulin sensitivity
- Higher circulating glucose
- Altered shifts in glucose storage and release from the liver
The hormones work together to create a balance, and that balance can shift over the course of the month.
Research suggests that when estrogen is higher and progesterone is lower, glucose patterns tend to be more stable. Luteal phase glucose can be higher as progesterone rises, even if daily habits stay the same.
What Happens When Hormones Rise and Fall Across the Cycle
A Harvard-led study of nearly 2,000 menstrual cycles found differences in glucose patterns by cycle phase. During the follicular phase, participants spent more time within the healthy glucose range and experienced higher glucose levels less frequently than during the luteal phase.
In contrast, the luteal phase (when progesterone is higher and estrogen is declining) was associated with slightly less time in range and more frequent elevations.
Another CGM-based study tracked glucose, hormones, steps, and symptoms across 149 cycles. Researchers noted the lowest mean glucose during the late follicular and the highest median glucose during the luteal phase.
Importantly, these trends remained constant after adjusting for age, BMI, weight, and self-reported PMS symptoms such as fatigue or bloating. Estrogen levels and daily step count were associated with lower glucose levels, whereas higher food cravings were associated with higher glucose levels.5
Why the Luteal (PMS) Phase Often Looks Different
The luteal phase is when progesterone peaks. From a biological standpoint, this is plausible, as progesterone supports energy storage and prepares the body for potential pregnancy.
Studies in both people without diabetes and those with type 1 diabetes show similar directional trends. For example, one study that examined women with type 1 diabetes found the late luteal phase corresponded with:4
- Higher mean glucose levels
- Slightly less time in range
- More time above target glucose levels
These differences weren’t explained by changes in exercise, insulin dosing, or carbohydrate intake. In other words, hormones may shift toward greater insulin resistance during PMS (or the luteal phase), even when behavior remains consistent.
PMS and Food Cravings
Research shows that appetite and food cravings tend to increase during the luteal phase of the menstrual cycle, corresponding with higher progesterone and lower estrogen levels.
For example, women report greater cravings for carbohydrate-rich, sweet, and high-fat foods in the luteal phase than in the follicular phase, and some studies suggest this may relate to hormonal effects on appetite regulation and neurotransmitter signaling, such as serotonin.
Changes in eating patterns can affect glucose data, as foods high in refined carbohydrates can lead to greater glucose spikes.
Lifestyle Factors That Influence PMS Glucose Variability
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Hormones provide a foundation for PMS-related glucose variability, but lifestyle factors can also influence these shifts.
Sleep, stress, movement, and meal timing all interact with hormonal shifts. During the luteal phase, when insulin sensitivity may already be slightly reduced, disruptions in these areas can amplify glucose swings. On the other hand, healthy habits can help buffer them.
For example:
- Sleep: Short or poor-quality sleep can raise glucose variability at any time of the cycle, but the effects may feel more noticeable during PMS.
- Stress: Psychological stress influences glucose levels through cortisol, which promotes glucose production and can reduce the effectiveness of insulin.
- Movement: Exercise makes the cells more insulin sensitive, helping the muscles take up glucose more effectively and reducing the amount of glucose circulating in the blood.
Hormones won’t override lifestyle habits, and habits don’t cancel out hormones. They work together in balance.
Using A CGM to Track PMS-Related Glucose Changes
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Using a CGM helps identify patterns at any time, particularly when examining connections between hormones and glucose metabolism.
Short-term changes during the luteal phase don’t necessarily raise health concerns. Month-to-month variability is expected, but it can be helpful to understand how your body changes throughout the month.
Instead of guessing whether PMS is affecting glucose, a CGM allows you to:
- Compare glucose trends across cycle phases
- See whether luteal-phase patterns repeat month to month
- Separate temporary shifts from longer-term trends
The goal isn’t to flatten every curve during PMS. It’s to understand what’s normal for you. CGM data is descriptive, not diagnostic. It helps you notice when patterns shift and how your body responds under different conditions. And once you see those patterns clearly, you’re better equipped to work with your physiology instead of fighting against it.
FAQs
1. Does PMS increase blood sugar levels?
PMS itself doesn’t cause changes in blood sugar. However, the same hormonal shifts that contribute to PMS, specifically changes in estrogen and progesterone, may temporarily increase blood glucose levels.
2. How do progesterone and estrogen affect glucose?
Estrogen is generally associated with improved insulin sensitivity, whereas higher progesterone levels may reduce sensitivity and lead to higher glucose levels in some individuals. The balance of these hormones throughout the menstrual cycle can influence the body's response to glucose.
3. Can a CGM track menstrual cycle-related glucose changes?
Yes, a CGM can show how glucose patterns shift across different phases of the menstrual cycle. It’s helpful to see how patterns change throughout the month and to compare differences between months.
4. How long do PMS-related glucose changes last?
PMS-related glucose changes typically occur during the late luteal phase (the end of the menstrual cycle leading up to menstruation) and resolve within a few days after your period begins. Once hormone levels reset, glucose patterns often return to baseline.
Topics discussed in this article:
References
- Rosen Vollmar, A. K., Mahalingaiah, S., & Jukic, A. M. (2025). The menstrual cycle is a vital sign across the lifespan. The Lancet. Obstetrics, gynaecology, & women's health, 1(2), e141–e145. https://doi.org/10.1016/j.lanogw.2025.100001
- Xega, V., & Liu, J. L. (2024). Beyond reproduction: unraveling the impact of sex hormones on cardiometabolic health. Medical review (2021), 4(4), 284–300. https://doi.org/10.1515/mr-2024-0012
- Ajjan R. A. (2024). The clinical importance of measuring glycaemic variability: Utilising new metrics to optimise glycaemic control. Diabetes, obesity & metabolism, 26 Suppl 7(Suppl 7), 3–16. https://doi.org/10.1111/dom.16098
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- Lin, G., Siddiqui, R., Lin, Z., Blodgett, J. M., Patel, S. N., Truong, K. N., & Mariakakis, A. (2023). Blood glucose variance measured by continuous glucose monitors across the menstrual cycle. NPJ digital medicine, 6(1), 140. https://doi.org/10.1038/s41746-023-00884-x
- Staff Writer. (2023, November 20). Studying the link between the menstrual cycle and blood sugar. Harvard T.H. Chan School of Public Health. https://hsph.harvard.edu/news/studying-the-link-between-the-menstrual-cycle-and-blood-sugar/
- Lin, G., Siddiqui, R., Lin, Z., Blodgett, J. M., Patel, S. N., Truong, K. N., & Mariakakis, A. (2023). Blood glucose variance measured by continuous glucose monitors across the menstrual cycle. NPJ digital medicine, 6(1), 140. https://doi.org/10.1038/s41746-023-00884-x
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