Foundayo™ and menstrual changes

Where cycles and pregnancy appear in Foundayo™ documents

Foundayo™ is a once-daily orforglipron tablet approved in the US for weight management in adults ^[1]. Neither the Prescribing Information nor the Medication Guide lists a menstrual side effect ^[1][2]. What the label does contain is a set of reproductive rules, summarised below. There is no EMA product information yet, after a positive opinion in October 2026, and Health Canada lists no Foundayo™ product, so no European or Canadian wording exists to compare ^[3][4].

Cycle entries in the trial registries

Women made up 64% of Trial 1 and 47% of Trial 2, the two weight trials behind the label ^[1]. The registries count menstrual events against the number of women in each group ^{[5][6][7][8][9]}. ATTAIN-1 lists non-serious events only above 5%, and no menstrual term reached that line; the smaller trials below list every event.

Reading the cycle entries

• Menstrual entries were single cases or pairs, scattered across placebo, dapagliflozin and orforglipron, with no dose pattern ^{[5][6][7][8][9]}.
• The cluster in ACHIEVE-1 sat on the 12 mg dose only; the higher 36 mg dose had none ^[7].
• Trials record what participants report, and many people do not mention cycle changes unless asked, so these counts may understate ordinary variation in every group.
• A few pregnancy-related serious events were recorded too, such as ectopic pregnancy on 6 mg in ATTAIN-1 and on 12 mg in ACHIEVE-1, and miscarriage on placebo and on 12 mg in ATTAIN-1 ^[5][7]. They are a reminder that pregnancies happened in the trials despite contraception rules.

The birth control pill rule in practice

Foundayo™ slows stomach emptying, most of all after the first dose, and the label says this could change how other oral medicines are absorbed ^[1]. No trial has measured the effect on birth control pills, so the label takes a cautious line: for 30 days after starting and for 30 days after each dose increase, it advises a non-oral method or an added barrier method ^[1]. It adds that hormonal contraception not taken by mouth should not be affected ^[1].

The dose rises in steps from 0.8 mg, with at least 30 days on each dose ^[1]. If your dose goes up every 30 days, those protection windows follow one another through the whole escalation period. The Medication Guide asks you to talk to your provider about which method suits you ^[2]. A missed period during these weeks is a reason for a pregnancy test, not a reason to assume the tablet is to blame ^[1][12].

Why a cycle might change on treatment

Weight change, in either direction: Foundayo™ is designed to lower body weight; in Trial 1, average weight fell by 7.4% to 11.1% on the three doses against 2.1% on placebo over 72 weeks ^[1]. MedlinePlus lists sudden large weight loss among the reasons periods stop, and notes that obesity also makes absent periods and abnormal bleeding more likely ^[12][13].

Eating much less: the label says Foundayo™ decreases food intake through lower appetite ^[1]. MedlinePlus links strict or extreme dieting and low body fat to missed periods ^[12]. No orforglipron study has measured hormones or ovulation.

Signals for other GLP-1 medicines: an analysis of US adverse event reports in women aged 12 to 55 found disproportionate reporting of heavy bleeding, bleeding between periods, menstrual clots and fewer periods with semaglutide, bleeding between periods and clots with tirzepatide, and no signals for liraglutide ^[10]. Such reports cannot show cause or frequency, and the abstract reports no finding for orforglipron.

PCOS: a 2026 meta-analysis of 11 randomised trials of GLP-1 medicines in women with polycystic ovary syndrome found modest weight loss but too little evidence to judge an effect on menstrual regularity ^[11]. It is a class finding, not one for Foundayo™.

Other common causes of period changes

MedlinePlus lists many causes of missed or irregular periods and of abnormal uterine bleeding ^[12][13][14]:

• Pregnancy, the most common cause of a missed period, and breastfeeding.
• Perimenopause and menopause; in their 40s, women may see periods come less often or closer together.
• Polycystic ovary syndrome, in which ovulation may not happen and periods can be irregular or absent.
• Hormonal birth control, including pills and hormonal IUDs, and stopping hormone shots.
• An overactive thyroid, pituitary problems, fibroids, polyps and infections of the uterus or cervix.
• Severe stress or anxiety, very heavy exercise and low body fat.

Practical steps when your cycle shifts

If a period is late, take a pregnancy test first; MedlinePlus says a pregnancy test is part of any check for missed periods ^[12]. If you are pregnant, the Foundayo™ label says to stop treatment, and the Medication Guide asks you to tell your provider and mentions a pregnancy exposure registry run by Eli Lilly ^[1][2].

MedlinePlus suggests seeing your provider if you miss more than one period, and contacting your provider about any unusual vaginal bleeding ^[12][13]. It describes heavy bleeding as soaking a pad or tampon every hour for two to three hours in a row, passing large clots or needing to change protection at night, and notes that long-term heavy loss can cause anaemia ^[13].

If you are planning a pregnancy, the label gives no stopping interval in advance, so the timing is a conversation to have with your prescriber ^[1]. The same applies to breastfeeding, which the label does not recommend during treatment ^[1].

Foundayo™ is a trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Eli Lilly and Company.