Can semaglutide or tirzepatide affect your period?

What do the FDA labels say?

The prescribing information for Wegovy and Ozempic, the two semaglutide injections, tables the adverse reactions seen in their trials. Nausea leads the list, reported by 44% of people on Wegovy 2.4 mg against 16% on placebo. No menstrual term appears anywhere in those tables or in the postmarketing section.¹² The same is true of Zepbound and Mounjaro, the two tirzepatide injections.³⁴

That absence is worth reading carefully. A label lists what the trials recorded often enough to report. It is not a study of the menstrual cycle, and none of these trials set out to measure one. So the labels say "not reported at a reportable rate", which is a narrower statement than "no effect".

The semaglutide guide and the tirzepatide guide cover what these molecules are, how the vials are labelled, and how the app tracks each one.

Can weight change alone shift a cycle?

Yes, and this is the part with the firmest footing. The Office on Women's Health states plainly that gaining too much weight or losing too much weight can cause missed periods, alongside stress, eating disorders, and polycystic ovary syndrome.⁵ The Endocrine Society's guideline on functional hypothalamic amenorrhea describes that condition as chronic anovulation often associated with stress, weight loss, excessive exercise, or a combination of them.⁶

The relationship runs in both directions. In a study of 120 women at an obesity clinic, with PCOS excluded, 18% had infrequent periods and 12% had none, and the odds of each roughly doubled with every step up in obesity grade.⁷ A body that is changing weight in either direction is a body whose cycle may change with it, and a GLP-1 protocol is, by design, a period of changing weight.

Two definitions help when deciding whether what you see is a change at all. The Office on Women's Health counts a cycle as irregular when it runs shorter than 24 days or longer than 38, or when its length varies by more than 20 days from month to month.⁵ A period that stops altogether has pregnancy on its list of causes, and that page recommends a doctor's visit to be sure.⁵

What do the safety reports show?

In July 2026, Frey and Etminan published an analysis of the FDA Adverse Event Reporting System in Obstetrics and Gynecology. They took every report filed for female patients aged 12 to 55, from the database's beginning through March 2026, and asked whether menstrual events were reported more often with each GLP-1 drug than with the database as a whole.⁸

Semaglutide showed the widest set of signals: heavy menstrual bleeding (reporting odds ratio 3.51), bleeding between periods (2.91), infrequent periods (3.09), menstrual clots (31.63, with a very wide confidence interval of 12.62 to 79.28), and anovulatory cycles (8.96, interval 2.20 to 36.51). Tirzepatide showed two narrower signals, for bleeding between periods (1.64) and clots (5.41). Liraglutide showed none.⁸

A reporting odds ratio is not a rate and not a cause. It says that, among the reports that were filed, menstrual events appeared more often than the database average. The authors say so themselves: confounding by indication cannot be excluded, because obesity independently affects menstrual regularity.⁸ A woman who starts semaglutide is often a woman whose cycle was already under the influence of weight, insulin resistance, or PCOS, and the report cannot separate the drug from the circumstances.

What is worth writing down?

The things a clinician will ask for, and the things memory loses first: the start and end date of each period, how heavy it was, the date and amount of each dose, and any symptom with the day it happened. Kept over time, that record lets a clinician see whether a change lines up with a dose change, a weight change, or neither.

Protocol Her is built around that record. Logging a period captures the start date, an end date when you have one, and a flow of Light, Medium, or Heavy, with an optional note. Once periods are logged, the home screen shows the current phase and cycle day, Analytics counts side effects and moods by phase, and in the clinician PDF the dose history and side-effect timeline each carry a cycle-phase column. That column is controlled by an "Include cycle data" switch on the export screen, decided fresh for every export.

Cycles that do not fit the average are handled rather than forced. The app estimates your cycle length from your own period dates and lets you set it by hand anywhere from 21 to 90 days. If no period is logged for one and a half cycle lengths, phase estimates pause instead of asserting a phase that is probably wrong. A "Not cycling right now" setting, with optional reasons of hormonal birth control, pregnancy, menopause or perimenopause, or prefer not to track, hides phase estimates everywhere, including on the clinician report, while period logging stays available.