Women taking GLP-1 medications sometimes report that their menstrual cycles change, but research examining those experiences has been limited.
A new analysis of reports submitted to the FDA has now identified several menstrual events that appeared disproportionately often with semaglutide, including heavy bleeding, bleeding between periods, menstrual clots, infrequent periods and cycles in which ovulation did not occur.
Tirzepatide also produced signals for some menstrual changes, but the pattern was narrower. Liraglutide, another GLP-1 medication, did not produce significant signals in the analysis.
The findings do not establish that any of these drugs caused the menstrual changes. Instead, they identify patterns strong enough to warrant more research and greater attention to menstrual health when these medications are prescribed to women of reproductive age.
Researchers analyzed reports involving women and girls ages 12 to 55
Researchers used the FDA Adverse Event Reporting System, commonly called FAERS, and examined reports involving female patients ages 12 through 55. The database collects suspected medication side effects reported by patients, clinicians, drug manufacturers and others.
The study included FAERS data available through March 2026 and focused on three medications: semaglutide, tirzepatide and liraglutide.
Rather than simply counting how many reports existed, the researchers used disproportionality and Bayesian analyses. These methods look for adverse events reported more frequently with a particular drug than would be expected compared with reporting patterns elsewhere in the database.
That makes FAERS useful for spotting possible safety signals, especially after millions of people begin using a medication. It cannot determine how frequently an event occurs among everyone taking the drug or prove that the drug caused it.
Takeaway: The researchers were looking for unusual reporting patterns, not measuring the actual percentage of GLP-1 users who experience menstrual changes.
Semaglutide showed the broadest menstrual signal
Among the three medications examined, semaglutide stood out because it was associated with disproportionate reporting across several different types of menstrual events. The signals included both changes in bleeding and changes related to the menstrual cycle itself.
Heavy menstrual bleeding appeared disproportionately in reports involving semaglutide. Researchers also identified signals for intermenstrual bleeding, meaning bleeding that occurs between expected periods, as well as reports involving menstrual blood clots.
The analysis also detected disproportionate reporting of oligomenorrhea, the medical term for menstrual periods that occur less frequently than expected.
Another signal involved anovulatory cycles. These are menstrual cycles in which an egg is not released, meaning ovulation does not occur even though other aspects of the cycle may still take place.
Takeaway: Semaglutide was linked to reporting signals involving heavier bleeding, bleeding between periods, clots, less frequent periods and cycles without ovulation.
Tirzepatide showed a different pattern
The findings were not identical across GLP-1 medications. Tirzepatide produced significant signals for bleeding between periods and menstrual clots, but researchers did not report the same broad range of menstrual signals seen with semaglutide.
That difference is important because GLP-1 medications are often discussed as though they are interchangeable. They act on related metabolic pathways, but they are different drugs and may not produce identical effects throughout the body.
Tirzepatide also acts on both GLP-1 and GIP receptors, while semaglutide targets the GLP-1 receptor. The current study was not designed to determine if those pharmacological differences explain the different reporting patterns.
The findings simply show that menstrual-event signals were not uniform across the drugs researchers examined.
Takeaway: Tirzepatide also produced menstrual safety signals, but they were limited to intermenstrual bleeding and menstrual clots in this analysis.
Liraglutide did not produce significant signals
Liraglutide provided another interesting comparison because researchers found no significant menstrual-event signals for the drug. That adds another reason not to treat every medication in the GLP-1 class as though its effects are necessarily identical.
The absence of a signal does not prove liraglutide cannot affect someone’s menstrual cycle. FAERS depends on events being noticed and reported, and differences in how long medications have been used, how often they are prescribed and which populations receive them can affect reporting patterns.
Still, the contrast gives researchers another question to investigate. If future studies confirm meaningful menstrual effects with some GLP-1 medications but not others, scientists will need to understand why.
That could eventually help clinicians make more individualized decisions for women concerned about bleeding, cycle regularity, ovulation or fertility.
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Takeaway: Liraglutide showed no significant menstrual reporting signals, suggesting possible differences within the GLP-1 medication class.
The study cannot tell us if semaglutide caused these changes
This is the most important limitation. An adverse-event report means that an event happened after or while someone was using a medication. It does not establish that the medication was responsible.
FAERS is a spontaneous reporting database, which means researchers do not know how many total people used each drug without experiencing a menstrual event. There is no reliable denominator that allows them to calculate the true incidence of heavy bleeding, missed ovulation or other menstrual problems among users.
Reporting can also be influenced by media coverage, awareness of possible side effects and the popularity of a medication. Underreporting is another major limitation because many people never submit reports about symptoms they experience.
Underlying health conditions could matter too. Obesity, PCOS, diabetes and rapid changes in body weight can themselves influence menstrual cycles, making it difficult to separate the medication from the health circumstances surrounding its use.
Takeaway: The analysis identifies potential safety signals, but it cannot prove that semaglutide or tirzepatide directly caused menstrual changes.
Weight loss itself may complicate the picture
Menstrual cycles are sensitive to changes in energy balance, body weight and metabolism. Because GLP-1 medications can produce substantial weight loss, some cycle changes could theoretically reflect the effects of losing weight rather than a direct action of the medication on reproductive biology.
Changes in insulin resistance may also affect ovulation, particularly in women with conditions such as PCOS. For some women, improving metabolic health could potentially make cycles more regular, while rapid weight loss or major energy changes could disrupt cycles in other circumstances.
That makes the real-world picture more complicated than simply asking if a GLP-1 drug “changes periods.” Different women may start treatment with very different metabolic, hormonal and reproductive profiles.
The new safety signals raise the possibility of additional drug-related effects, but controlled studies would be needed to separate those effects from weight loss, underlying conditions and other medications.
Takeaway: Menstrual changes during GLP-1 treatment could involve the drug itself, weight loss, metabolic improvement, underlying reproductive conditions or several factors at once.
Changes in ovulation could have fertility implications
The anovulatory-cycle signal may attract particular attention because ovulation is directly connected with fertility. If future research confirms that semaglutide can affect ovulation in some women, the implications could extend beyond changes in when a period arrives.
At the same time, researchers cannot conclude from these adverse-event reports that semaglutide routinely suppresses ovulation or reduces fertility.
In some women with obesity or PCOS, weight loss and improved insulin sensitivity may actually improve ovulatory function. That means different biological forces could be operating in different groups of patients.
Anyone experiencing major cycle changes while trying to conceive may benefit from discussing the timing and pattern with a clinician rather than assuming either that the medication is responsible or that the change is harmless.
Takeaway: Reports of anovulatory cycles raise important fertility questions, but the study does not establish that semaglutide prevents ovulation or causes infertility.
Menstrual health may need a bigger place in GLP-1 conversations
GLP-1 medications are now used by large numbers of women, yet conversations about side effects tend to focus heavily on nausea, vomiting, constipation and other gastrointestinal symptoms. This study suggests menstrual patterns may deserve more attention as researchers continue monitoring the drugs.
For a woman whose normally predictable period suddenly becomes extremely heavy, begins arriving irregularly or disappears, that change can affect daily life and may carry medical significance regardless of what caused it.
The researchers suggest menstrual health could become part of counseling for reproductive-aged patients using GLP-1 medications. Future prospective research will be needed to determine which changes truly occur more often, how common they are and if particular women face greater risk.
For now, the study offers an early signal rather than a final answer. It gives researchers a reason to look much more closely at a part of GLP-1 treatment that women themselves may notice long before science fully understands it.
Question for you. If a medication could affect your menstrual cycle or ovulation, would you want your doctor to discuss that possibility before you started taking it?
