GLP-1s and Menstrual Bleeding: Perimenopause & Cycle Changes

Why bleeding changes can feel confusing in perimenopause

As estrogen and progesterone levels fluctuate during perimenopause, ovulation becomes less predictable, and your menstrual cycles may become irregular. Your periods might be shorter or longer than they used to be, with heavier or lighter bleeding. As you get closer to menopause, you may even start skipping periods entirely. 

Other conditions like fibroids, endometrial polyps, and adenomyosis, as well as hormonal contraception or hormone replacement therapy (HRT), can also affect bleeding patterns. Sometimes, more than one of these factors is involved at the same time. With so many potential causes, it can be difficult to tell whether a change in bleeding is related to perimenopause, a medication, or another medical condition. That's why it's important to discuss new or unusual bleeding with your healthcare provider. 

“Weight loss—whether from lifestyle changes or weight-loss medications like GLP-1s—can sometimes affect your menstrual cycle, particularly if you have PCOS or have cycles without ovulation. As weight and insulin sensitivity improve, hormone levels can shift and ovulation may return, which can lead to more regular periods. If your periods have been absent for a while, that first period may sometimes be heavier or irregular as your cycle gets back on track.” –Kathryn Williams, MD, MSCP, DABOM

Are GLP-1s Connected to Menstrual Bleeding?

A recent analysis explored whether GLP-1 medications could be associated with reports of menstrual bleeding changes and other menstrual events. To understand what the researchers found, it helps to first understand where the information came from.

What is FAERS?

The FDA Adverse Event Reporting System (FAERS) is a national database that collects reports of possible side effects and other adverse events associated with medications. Reports can be submitted by healthcare professionals, patients, caregivers, and manufacturers, with manufacturers required to report certain adverse events to the FDA.

Researchers use FAERS to look for safety signals which are patterns that may suggest a medication deserves closer study. However, FAERS cannot determine whether a medication actually caused a reported event. Many other factors may explain why an event occurred.

Say a lot of people report headaches after starting a new allergy medication during a week of record pollen. FAERS can show the headaches were reported, but not whether the medication, the pollen, or something else entirely caused them. That takes more research.

What did researchers find?

Researchers recently analyzed FAERS reports involving women ages 12 to 55 who were taking semaglutide, tirzepatide, or liraglutide. They found several potential menstrual safety signals, but the findings differed by medication. 

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Semaglutide was associated with disproportionate reporting of several menstrual events, including heavy menstrual bleeding and bleeding between periods. Tirzepatide showed signals for bleeding between periods and menstrual clots, while liraglutide did not show significant menstrual signals. These findings cannot establish that any of the medications caused the reported events, and the researchers emphasized the need for further studies to determine the actual incidence and risk.

When bleeding changes should prompt medical evaluation

Changes in menstrual cycles are common during perimenopause and are not always a reason for concern. However, some bleeding patterns deserve attention. 

Heavy bleeding that soaks through a pad or tampon in 1–2 hours, especially if you're feeling dizzy, lightheaded, or faint, should be evaluated promptly. Persistent bleeding after intercourse should also be checked by your healthcare provider.

Menopause is defined as 12 consecutive months without a menstrual period. Once you've reached menopause, any vaginal bleeding is considered abnormal and should be evaluated by a doctor.

How hormone therapy and cycle regulation fit into the picture

Hormone replacement therapy (HRT)  and hormonal contraceptives can also affect your bleeding patterns, particularly during the first several months after starting or changing treatment.

Because some women use HRT, hormonal contraception, and GLP-1 medications at the same time, it isn't always easy to identify a single cause of unexpected bleeding. Your menopause-specialized doctor can help evaluate the full picture.

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What If You Already Had Irregular Periods Before Starting a GLP-1?

If your periods were already irregular before starting a GLP-1 medication, it may be even harder to recognize whether something has changed. Talking with your healthcare provider about your usual menstrual patterns, medical history, and other medications can help establish what is normal for you.

Some questions worth considering include:

• What were your periods like before starting the medication?

• When did the bleeding begin?

• How heavy is the bleeding?

• Have you recently started or changed hormone therapy?

• Could you be pregnant?

• Do you have fibroids or another uterine condition?

• Are you taking medications that affect bleeding?

The Bottom Line on GLP-1s and Unexpected Bleeding

Researchers have identified potential menstrual safety signals with some GLP-1 medications, but we don't yet know whether these medications caused the reported events or how often they occur.

What we do know is that bleeding changes are common during perimenopause, and several factors may contribute. If you notice new or concerning bleeding, talk with your healthcare provider rather than assuming it's caused by menopause or your medication.

If you have questions about bleeding changes or GLP-1s, Alloy can connect you with a menopause-specialized doctor who can look at the whole picture with evidence-based guidance.

Frequently Asked Questions

Can GLP-1 medications cause changes in menstrual bleeding?

Researchers analyzing FAERS reports identified potential menstrual safety signals with certain GLP-1 medications, such as heavy bleeding and spotting between periods with semaglutide, as well as spotting and clots with tirzepatide. However, FAERS data only identifies patterns for further investigation and cannot prove that the medications directly caused the bleeding events. In addition, weight loss and improved insulin sensitivity can shift hormone levels and trigger the return of ovulation, which may result in an irregular or heavier period as your cycle resets.

Why is unexpected bleeding especially difficult to pinpoint during perimenopause?

Natural fluctuations in estrogen and progesterone already make ovulation and cycle lengths unpredictable during perimenopause. Bleeding patterns can also be altered simultaneously by underlying uterine conditions such as fibroids, endometrial polyps, and adenomyosis, as well as treatments like hormone replacement therapy (HRT), hormonal birth control, or GLP-1 medications. When multiple factors are present at the same time, determining the exact cause of a bleeding change requires an evaluation by a healthcare provider.

When should menstrual or vaginal bleeding be evaluated by a doctor?

You should seek prompt medical evaluation if your bleeding is heavy enough to soak through a pad or tampon in 1–2 hours, especially if you experience lightheadedness, dizziness, or faintness. Persistent bleeding after intercourse also requires medical attention. Additionally, because menopause is reached after 12 consecutive months without a period, any vaginal bleeding that occurs after this milestone is considered abnormal and must be checked by a physician.

References

1. Frey C, Etminan M. Association of glucagon-like peptide-1 receptor agonists with menstrual events in reproductive-aged patients. Obstet Gynecol. Published online 2026. doi:10.1097/AOG.0000000000006367. 

2. Santoro N, Roeca C, Peters BA, Neal-Perry G. The menopause transition: signs, symptoms, and management options. J Clin Endocrinol Metab. 2021;106(1):1-15. doi:10.1210/clinem/dgaa764

3. Munro MG, Critchley HOD, Fraser IS; FIGO Menstrual Disorders Committee. The two FIGO systems for normal and abnormal uterine bleeding symptoms and classification of causes of abnormal uterine bleeding in the reproductive years: 2018 revisions. Int J Gynaecol Obstet. 2018;143(3):393-408. doi:10.1002/ijgo.12666

4. Practice bulletin no. 128: diagnosis of abnormal uterine bleeding in reproductive-aged women. Obstet Gynecol. 2012;120(1):197-206. doi:10.1097/AOG.0b013e318262e320

5. Makkena HB. Comparative gynecological safety of the dual GIP/GLP-1 receptor agonist tirzepatide vs. the GLP-1 receptor agonist semaglutide: a real-world pharmacovigilance analysis (2022-2025). Cureus. 2026;18(1):e101738. doi:10.7759/cureus.101738

6. US Food and Drug Administration. FDA Adverse Event Monitoring System (AEMS) public dashboard. Published March 11, 2026. Accessed July 31, 2026. https://www.fda.gov/drugs/fda-adverse-event-monitoring-system-aems/fda-adverse-event-monitoring-system-aems-public-dashboard

7. ACOG committee opinion no. 557: management of acute abnormal uterine bleeding in nonpregnant reproductive-aged women. Obstet Gynecol. 2013;121(4):891-896. doi:10.1097/01.AOG.0000428646.67925.9a

8. Manley K, Hillard T, Clark J, et al. Management of unscheduled bleeding on HRT: a joint guideline on behalf of the British Menopause Society, Royal College Obstetricians and Gynaecologists, British Gynaecological Cancer Society, British Society for Gynaecological Endoscopy, Faculty of Sexual and Reproductive Health, Royal College of General Practitioners and Getting it Right First Time. Post Reprod Health. 2024;30(2):95-116. doi:10.1177/20533691241254413