Wegovy® (injection) and menstrual changes

What the Wegovy® documents say about cycles

There is no menstrual row in the US adult or adolescent tables, the EU frequency table or the Canadian table. ^[1][2][3] That leaves the reproductive sections, which say more than many readers expect.

The animal finding, read carefully

In a rat study of fertility and early development, females given semaglutide had longer oestrous cycles at every dose and, at higher doses, a small reduction in corpora lutea, the structures left after ovulation. The US label calls these effects likely an adaptive response to the medicine’s effect on food intake and body weight. Male fertility was not affected. ^[1] The EU summary says the effect of semaglutide on human fertility is unknown. ^[2]

Animal reproductive cycles do not map directly onto human periods, so this is a clue about mechanism, not evidence that Wegovy® changes human cycles.

Evidence from PCOS

Polycystic ovary syndrome often causes irregular or absent periods. In a randomised, open-label trial in China, 100 women with PCOS and overweight or obesity received metformin alone or metformin plus semaglutide 1 mg weekly for 16 weeks; 80 completed. The combination group lost more weight, had larger falls in testosterone and showed higher rates of menstrual cycle recovery. Between weeks 16 and 40, when everyone took metformin alone, natural pregnancy rates were 35% versus 15%. ^[4]

The study was modest in size, used a lower semaglutide dose than Wegovy® and combined it with metformin, so it cannot be read as a Wegovy® result. It does show why periods that return or become regular can also mean fertility returns. In the STEP 3 weight trial, 14.7% of participants had a menstrual disorder recorded at the start. ^[3]

Why a cycle might shift

• Supported by the label: semaglutide reduces food intake and body weight, and in animals the cycle changes were tied to exactly that. ^[1]
• Proposed: MedlinePlus lists both obesity and sudden large weight loss among things that make absent periods more likely, ^[5] so weight change in either direction can disturb a cycle. How much this applies to Wegovy® users has not been measured.
• General: stress, intense exercise, thyroid problems, PCOS (which MedlinePlus now also calls polyendocrine metabolic ovarian syndrome), stopping hormonal contraception, breastfeeding and the approach to menopause all change periods. Pregnancy is the most common cause of a missed period. ^[5]

Pregnancy rules that come with Wegovy®

Wegovy® should not be used in pregnancy for weight reduction. The US label says weight loss offers no benefit during pregnancy and may harm the fetus, and that Wegovy® should be stopped when a pregnancy is recognised. It also asks people to stop at least 2 months before a planned pregnancy because semaglutide stays in the body for a long time. ^[1] A pregnancy registry collects outcomes for people exposed during pregnancy. ^[1]

The EU summary recommends contraception for women who could become pregnant while using semaglutide. ^[2] The US label reports no clinically significant change in the levels of two common pill hormones when taken with semaglutide. ^[1] Questions about your own method belong with your prescriber or pharmacist.

Keeping track, and what general guidance says

MedlinePlus suggests recording your period each month so you know your usual pattern and can spot changes. It advises talking with a provider about major changes in your cycle, very heavy bleeding or severe pain, which can signal other health problems. ^[6] If more than one period is missed, it advises seeing your primary or women’s health provider. ^[5]

Treatment of absent periods depends on the cause, and periods usually return once that cause is treated. ^[5] A provider will usually check for pregnancy first. ^[5]

Wegovy® is a registered trademark of Novo Nordisk A/S. PepLabo is not affiliated with or endorsed by Novo Nordisk.

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