What the three documents cover
Menstrual problems appear nowhere in the US adverse reaction text, the EU frequency table or the Canadian event tables for Trulicity®. [1][3][4] What the documents do discuss is the pill, pregnancy and animal fertility findings, summarised below.
| Topic | What the document says | Source |
|---|---|---|
| Period changes as a side effect | Not listed in the US, EU or Canadian adverse reaction data | US label, EU SmPC, Canadian monograph [1][3][4] |
| Combined contraceptive pill with 1.5 mg | Peak hormone levels 26% and 13% lower, reached later; total exposure unchanged; no pill dose adjustment needed | EU SmPC 4.5; Canadian monograph 9.4 [3][4] |
| Other oral medicines at 3 mg and 4.5 mg | Limited experience; slowed stomach emptying may delay absorption | US label 7.1 [1] |
| Contraception | Women who could become pregnant should use contraception during treatment | EU leaflet, section 2 [3] |
| Pregnancy | EU: not recommended. US: only if the potential benefit justifies the risk to the fetus | EU SmPC 4.6; US label 8.1 [1][3] |
| Female rat fertility studies | More females with a longer resting phase of the cycle and fewer corpora lutea (structures left after ovulation) at 13 or more times human exposure, alongside reduced food intake | US label 13.1; EU SmPC 5.3 [1][3] |
The pill study in detail
Because dulaglutide slows stomach emptying, researchers tested whether it changes how oral medicines are absorbed. In healthy volunteers, a combined pill containing norgestimate and ethinyl estradiol was given with and without a 1.5 mg dose. [5] The overall amount of each hormone reaching the blood was unchanged; peak levels of norelgestromin and ethinyl estradiol dropped by 26% and 13%, and the peaks came about 2 hours and 0.3 hours later. [3][4] The study authors and both regulators concluded that no adjustment to the pill is needed. [3][4][5]
Two limits are worth knowing. The test used one product and one dose; the US label says experience with other oral medicines at 3 mg and 4.5 mg is limited, and that the delay in stomach emptying is largest after the first dose and smaller after later ones. [1] None of the Trulicity® documents addresses what happens to a pill if you vomit soon after taking it. If you rely on a pill and are vomiting, or you are moving to a higher dose, ask your pharmacist or prescriber whether anything changes for your method.
Evidence about cycles themselves
The most specific data come from the FDA Adverse Event Reporting System. A 2026 analysis of reports from mid-2022 to mid-2025 compared six GLP-1 medicines. Semaglutide showed more reports than expected for several menstrual and hormonal problems, whereas dulaglutide showed fewer than expected for painful periods (adjusted reporting odds ratio 0.13) and heavy menstrual bleeding (0.39). Dulaglutide did have more reports than expected of polycystic ovaries; for the similar pattern with semaglutide, the authors pointed to the conditions people were being treated for rather than a drug effect. [6] A separate 2026 study in women aged 12 to 55 found menstrual signals for semaglutide and tirzepatide and none for liraglutide; its summary does not report a result for dulaglutide. [7]
Reporting databases reflect who chooses to file a report, cannot count how many people take each medicine, and cannot show cause. A lower-than-expected figure is not proof that Trulicity® protects the cycle, and an absence of reports is not proof that changes never happen.
A trial in polycystic ovary syndrome
Polycystic ovary syndrome (PCOS) often causes infrequent periods, and diabetes and PCOS frequently occur together. A single-centre, open-label trial randomised 68 women with PCOS and overweight or obesity to dulaglutide plus a calorie-restricted diet or the diet alone, for up to 6 months or until they lost 7% of their weight. [8]
Women on dulaglutide reached the weight goal faster and had better blood glucose measures, but changes in menstrual frequency, hormone markers, liver fat and body composition did not differ significantly between the groups. Nausea, vomiting, constipation and loss of appetite were the main side effects. The authors saw dulaglutide as a possible add-on to diet rather than a replacement for it. [8] Trulicity® is not approved to treat PCOS; the trial helps answer whether it disrupted cycles in this group, and over this period it did not appear to.
Why a cycle might shift
- Label-supported: dulaglutide slows stomach emptying, which is why the pill study was done, and the delay is largest after the first dose (sections 7.1 and 12.2). [1] In female rats, a longer resting phase of the cycle appeared only at high exposures and together with reduced eating and weight gain. [1][3]
- Proposed, not established: the authors of the 2026 reporting study speculated that the lower menstrual reporting with dulaglutide might point to a favourable influence on the link between metabolism and reproduction, and called for prospective research to test it. [6]
- General background: MedlinePlus lists a weight gain or loss of more than about 4.5 kg among causes of irregular bleeding, and sudden weight loss, intense exercise and severe stress among causes of missed periods. [10][11] Changes in eating or weight during treatment can therefore matter more than the drug itself.
Other causes to keep in mind
Pregnancy is the most common reason for periods to stop, followed by breastfeeding and the menopause; hormonal contraception, some cancer medicines and medicines for psychosis, low body fat, and conditions affecting the ovaries can also stop periods. [11] For irregular or heavy bleeding, MedlinePlus lists hormone imbalance, a thickened womb lining, fibroids or polyps, infection, bleeding disorders, hormonal contraception including IUDs, and less often cancer; being overweight also makes irregular bleeding more likely. [10]
Age matters too. Trulicity® is approved in the US for young people from age 10, and MedlinePlus notes that periods can take a few years to become regular after they start, while cycles often change in the forties as the menopause approaches. [1][9][10]
Practical steps from the sources
MedlinePlus suggests keeping track of your period each month so you know your usual pattern and can spot changes, and talking with a provider about major changes, very heavy bleeding or severe pain. If you miss more than one period, it advises seeing your primary or women’s health provider, and a pregnancy test is part of that check. [9][11]
For Trulicity® specifically, the Medication Guide asks you to tell your healthcare provider if you are pregnant, plan to become pregnant or become pregnant during treatment. [2] The EU leaflet adds that women who could become pregnant should use contraception while using dulaglutide and asks you to discuss with your doctor how to manage blood sugar during pregnancy. [3] Whether and when to stop or switch is a decision for your prescriber.
Trulicity® is a registered trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Eli Lilly and Company.
When to get help
The signs and contact information below come from this article’s sourced guidance.
Emergency
- Severe belly pain that will not go away, with or without vomiting, sometimes reaching the back (not your usual period cramps)
Contact: Stop Trulicity® and call your prescriber straight away; emergency care if you cannot reach them
Medication Guide [2]