Retatrutide and the Menstrual Cycle, Contraception, Fertility and Pregnancy: What the Trials Excluded, What the GLP-1 Labels Say, and What the Threads Ask

Most GLP-1-class questions can be answered from a label. This one cannot: retatrutide has no marketing authorization anywhere, so no pregnancy, lactation or contraception section exists for it. What exists is the eligibility record of its trials, two posted adverse-event tables, the labels of neighboring compounds, and cyclic physiology measured in women taking nothing at all. This article gives no advice and calls no exposure safe or unsafe. See also our approval status article.

What the threads actually ask

Our post set holds 108 unique threads from 12 subreddits, created 6 August 2025 to 31 August 2026 (source 11), most of it from r/Retatrutide (31 posts), r/Biohackers (28) and r/tirzepatidecompound (10). It needs cleaning: 67 of the 108 are off topic once read, leaving 41 with cycle, contraception, fertility, pregnancy, miscarriage or libido content, and five duplicate groups add 10 copies, so the deduplicated list is 98 posts. No count here is a count of people, and none is a rate.

Eight questions recur, and the compound in the title is not always retatrutide. Cycle timing: "Delayed period?" (r/Retatrutide, August 2026) and "Wife on reta, missed periods" (June 2026), one poster writing "she’s now missed two periods and it’s starting to scare us". Flow, in both directions and mostly under tirzepatide: "Girls- Abnormal bleeding?" and "Ladies only- reduced flow?" (r/tirzepatidecompound, November 2025 and April 2026), the heavy end "I bled for almost a month straight with clotting to the point I had to see a doctor.", the light end "my period is so light (kind of like spotting)". Luteal hunger: "Reta doesn’t work during my luteal phase" (r/Retatrutide, August 2026), where "The second my luteal phase hits I’m RAVENOUS and it feels like I am not even on reta at all." The pill: "reta + oral birth control??" (r/Biohacking, August 2026) and "Reta and Tirzepatide reduce the effectiveness of birth control pills" (r/Retatrutide, February 2026), naming "the slower gastric emptying could meaningfully affect absorption of the hormones". Conceiving, in "Pregnancy or Trying to Conceive After Reta" (October 2025), where a washout figure circulates as lore: "I believe it’s recommended to be off of the medication for at least 2 months before trying to conceive." Then "Conceived on Retatrutide" (July 2026), "GLP after miscarriage" (August 2026) and "Husband is unhappy with the sex drive loss from reta" (January 2026).

Three caveats travel with it. These are anonymous self-reports without medical confirmation, and the material is research-grade retatrutide from grey-market sources, so identity, dose and purity are unverified. Many posters take other peptides, contraceptives or hormones at once, disclosing "I’m also on TRT" and "I’m on HRT and not bodybuilding levels". And the lore is thin where checkable: most posts repeating a washout figure name no doctor, study, label, insert or link, and none attributes a pregnancy loss to the compound. Reddit is a demand signal, never a citation; our corpus analysis covers the method.

What the retatrutide trials required, and what they excluded

The registry records are the only reproductive rulebook retatrutide has. Sex is "ALL" in the records screened, minimum age "18 Years" except in the cardiovascular and kidney outcomes trial, which starts at "45 Years" (source 5). Only two publish a reproductive criterion.

Nine Lilly records, TRIUMPH included, were screened live on 4 September 2026 for pregnan, contracept, childbear, breastfeed, lactat and menstrua, with zero matches in each (source 5). Absence in a posted summary is not proof that the protocols lacked such rules, and a keyword search there gives a false positive, since "Female Urogenital Diseases and Pregnancy Complications" is only a MeSH ancestor term.

The peer-reviewed papers are silent on contraception. The obesity report states "We enrolled 338 adults, 51.8% of whom were men." (PMID 37366315), the diabetes report gives "156 [56%] female" among "281 participants" (PMID 37385280), and the liver substudy discloses that "An upper limit of 60% enrollment of women was used to ensure a sufficiently large sample of men." was applied in the parent trial (PMID 38858523). None of the three returns a hit for contracept or pregnan.

Only two of the thirty-four retatrutide records post results; both were rescreened for twelve strings including menstrua, amenorrh, metrorrhag, vaginal, ovarian, libido and sexual. Only vaginal matched: "Vaginal infection" in 1 of 15 at risk in the 4 mg obesity arm, plus "Erectile dysfunction" in 2 of 36 in the 1 mg arm (NCT04881760), and "Vaginal infection" in 1 of 15 with "Vaginal haemorrhage" in 1 of 16 in retatrutide arms of the diabetes trial (NCT04867785). No menstrual term appears in either table.

Lilly's expanded-access record calls retatrutide investigational (NCT07629401) and the FDA states that it "cannot be used in compounding under federal law" (source 2). As of 4 September 2026, no completed study located documents a marketing authorization or approved product containing retatrutide in any jurisdiction, openFDA returning "No matches found!" (source 15).

Luteal-phase hunger: measured without any drug, unmeasured with one

The threads' complaint has a measured counterpart in women taking nothing.

The only cycle-timed dosing experiment located is in animals: in female rats, dosing during proestrus and estrus rather than metestrus and diestrus "enhanced the intake-suppressive effects of liraglutide and semaglutide" (PMID 41017581). That is an estrous cycle, and its authors put the transfer no higher than a possibility.

As of 4 September 2026, no completed study located reports appetite, energy intake or weight outcomes of a GLP-1, GIP or glucagon receptor agonist stratified by menstrual cycle phase in humans. The PubMed search (retatrutide OR semaglutide OR tirzepatide OR liraglutide OR "GLP-1 receptor agonist*") AND (luteal OR follicular OR "menstrual cycle") AND (appetite OR "energy intake" OR "weight loss" OR "body weight") returned 19 results, made up of PCOS or fertility studies, reviews, case reports and animal work, and the ClinicalTrials.gov search AREA[InterventionName](retatrutide OR semaglutide OR tirzepatide OR liraglutide) AND (menstrual OR luteal OR follicular) returned 20 records, none of them carrying a cycle-phase-stratified endpoint (source 20).

Cycle timing and flow: a class signal, and not one retatrutide datapoint

Three kinds of source touch menstrual change outside retatrutide. The first two rest on self-reports collected outside any randomized design; the third is randomized trial work in PCOS.

The first is a large text analysis of forum material, whose preprint text reports that "Nearly 4% of Reddit users with side effects reported reproductive symptoms, notably menstrual changes like intermenstrual bleeding (0.9%), heavy bleeding (0.9%), and irregular cycles (0.7%). These rates would be higher in female-only samples." (source 21). The preprint states its own limit: "because users were not prompted to disclose all side effects, we cannot estimate their true prevalence". It covers semaglutide and tirzepatide, its denominator is mixed-sex, and the peer-reviewed version in Nature Health carries no PubMed identifier as of 4 September 2026, so the wording quoted here is the preprint text (source 21).

The second is spontaneous-report signal detection. A FAERS study "restricted to female patients aged 12-55 years" found that "Semaglutide demonstrated the broadest signal profile, with disproportionate reporting of heavy menstrual bleeding, intermenstrual bleeding, menstrual clots, oligomenorrhea, and anovulatory cycles. Tirzepatide generated signals for intermenstrual bleeding and menstrual clots. Liraglutide produced no significant signals." (PMID 42424619). Disproportionality is a reporting pattern, not an incidence.

The third is the PCOS literature, the only place where menstrual outcomes were counted prospectively, and it is liraglutide work. A 2025 scoping review summarizes a randomized trial in "52 patients with PCOS aged 18-40 years old" on metformin with or without liraglutide over 12 weeks, reporting "a 52% and 88% improvement in menstrual cycle recovery rates in the metformin and combination groups, respectively", and a placebo-controlled trial in 92 women over 32 weeks in which menses occurrence improved on liraglutide and was unchanged in the control group (PMID 41141001). Endpoints were not standardized, and the 2026 review pooling 11 randomized trials is blunt: "evidence was insufficient to draw conclusion regarding glucose, insulin, hirsutism, and menstrual regularity" (PMID 41701618, Prospero CRD42024535096). One phase 4 trial now puts the outcome first: 198 women aged 18 to 45, primary outcome "Improvement of ovarian dysfunction as defined by menstrual irregularity in overweight or obesity-related PCOS" at 72 weeks, University of Bonn, recruiting with no results posted (NCT07326111).

None of that is retatrutide data: every finding above belongs to semaglutide, tirzepatide or liraglutide, and carrying it across is a class assumption.

The pill: what the tirzepatide label instructs, and why

The Mounjaro prescribing information states, verbatim: "Use of MOUNJARO may reduce the efficacy of oral hormonal contraceptives due to delayed gastric emptying. This delay is largest after the first dose and diminishes over time." (source 8). The instruction that follows appears in the Zepbound label as "Advise patients using oral hormonal contraceptives to switch to a non-oral contraceptive method, or add a barrier method of contraception for 4 weeks after initiation with ZEPBOUND and for 4 weeks after each dose escalation" (source 9), repeated in both labels' oral-medications and counseling sections.

The numbers behind it live only in the label. With "a combined oral contraceptive (0.035 mg ethinyl estradiol and 0.25 mg norgestimate) in the presence of a single dose of tirzepatide 5 mg, mean Cmax of ethinyl estradiol, norgestimate, and norelgestromin was reduced by 59%, 66%, and 55%, while mean AUC was reduced by 20%, 21%, and 23%, respectively.", and "A delay in tmax of 2.5 to 4.5 hours was observed." (source 9): large peak reductions, much smaller exposure reductions, one dose. A review confirms the same direction (PMID 37940101); no standalone publication of that trial was located on 4 September 2026 (source 27).

Semaglutide's label reads differently. The Ozempic label states "No clinically relevant drug-drug interaction with semaglutide (Figure 4) was observed based on the evaluated medications", its caption noting that "Metformin and oral contraceptive drug (ethinylestradiol/levonorgestrel) were assessed at steady state." (source 10). A live check found exactly one occurrence of contracept in that whole label, in that caption, with no contraception subheading and no Highlights contraception line. The tirzepatide instruction is tirzepatide's.

Retatrutide has neither instruction, neither number, and no label to carry either. As of 4 September 2026, no completed study located reports pregnancy, fertility, contraception-failure or menstrual-cycle outcomes for retatrutide: the PubMed search (retatrutide[tiab] OR LY3437943[tiab]) AND (pregnan*[tiab] OR contracept*[tiab] OR menstrua*[tiab] OR amenorrh*[tiab] OR fertilit*[tiab] OR libido[tiab] OR "sexual function"[tiab]) returned one hit, a dermatology practice review rather than a retatrutide trial, and the ClinicalTrials.gov search query.intr=retatrutide OR LY3437943 with query.term=pregnancy OR contraception OR menstrual returned three records whose outcome lists carry zero reproductive endpoints (source 15). Posters close that gap by transferring the tirzepatide wording across, which is their assumption, not a measurement. Our GLP-1 safety article covers class transfer.

Fertility, trying to conceive, and sexual desire

The only fertility-adjacent outcomes measured here are the PCOS ones above, plus ovulation frequency by weekly serum progesterone as a key secondary outcome of that phase 4 trial (NCT07326111): all liraglutide or unfinished, none retatrutide.

What the retatrutide record contains on fertility is an exclusion criterion. Women of childbearing potential without adequate contraception were kept out of the phase 2 obesity trial (NCT04881760); men and women alike were bound to contraception in the phase 1 renal record, which also excluded lactating women and anyone with a positive pregnancy test (NCT05611957). Those are eligibility rules rather than endpoints: the three registry records that a pregnancy, contraception or menstrual search matches carry zero reproductive endpoints (source 15).

Sexual desire sits adjacent, and it is the most retatrutide-specific of the themes in our set. The only peer-reviewed account located is a 2026 narrative review explicit about its status: the authors "established a theoretical model for how GLP-1 agonist modulation via increased serotonergic activity at the 5-HT2C receptor may result in diminished sexual desire", and state that "Forecasted changes in sexual desire illustrated in Fig. 1 are not rooted in quantitative evidence" (PMID 41404471). The posted retatrutide tables contain no libido or sexual term, and the community reports are confounded by hormone therapy their own authors disclose.

Pregnancy and breastfeeding: what the labels say, what the cohorts found, and what retatrutide has

Approved labels in this class say three things about their own products.

The tirzepatide label reports "fetal growth reductions and fetal abnormalities" in "pregnant rats administered tirzepatide during organogenesis ... based on AUC" (source 8); the Wegovy label reports "embryofetal mortality, structural abnormalities and alterations to growth" in pregnant rats "at clinically relevant maternal exposures" (source 29). Both obesity labels run a pregnancy exposure registry (source 9, source 29). Retatrutide has no label to carry such a sentence.

On breastfeeding the two differ in what was studied, not in what was found. A single-dose lactation study reported that "the concentration of tirzepatide in breast milk was found to be either undetectable or low compared to the maternal administered dose" (source 8), while the semaglutide injection label states: "There are no data on the presence of semaglutide in human milk, the effects on the breastfed infant, or the effects on milk production." (source 10). Retatrutide has neither study nor sentence, only the rule excluding lactating women (NCT05611957).

Periconception cohort work exists for the class, reported with its designs and caveats, not as reassurance. Against insulin, the adjusted risk ratio for major congenital malformations in the GLP-1 receptor agonist arm was "0.95 (95% CI, 0.72-1.26)" across 938 exposed infants, the authors hedging that results "did not indicate a large increased risk of MCMs above the risk conferred by maternal T2D requiring second-line treatment." (PMID 38079178). A prospective cohort of 168 first-trimester-exposed pregnancies found no association with major birth defects against diabetes controls, "adjusted OR, 0.98 (95% CI, 0.16 to 5.82)" (PMID 38663923). A meta-analysis of "286,599 women (43,577 exposed and 243,022 unexposed)" reports "no significant difference in MCM risk ... (relative risk (RR): 1.02, 95% CI: 0.96-1.08)" and warns that "these findings should not be interpreted as proof of safety" (PMID 42447044). A target trial emulation across "3572 pregnancies" gave "1.29 (CI, 0.82 to 2.06) for SGA, 1.08 (CI, 0.84 to 1.40) for LGA, and 1.21 (CI, 0.83 to 1.82) for MCM." (PMID 42258827). Observational designs, class-level exposures, no retatrutide arm.

One trap: DailyMed lists retatrutide entries that look like a US label and are not, ten filings by a Chinese e-commerce firm, "RETATRUTIDE PEN INJECTION, SOLUTION [GUANGZHOU YIXIN CROSS-BORDER E-COMMERCE CO., LTD.]", whose approval element reads "Export only" (source 34), with no pregnancy or lactation section. For retatrutide and pregnancy the record is an exclusion criterion in two trials and an absence of posted reproductive endpoints in the rest; as of 4 September 2026, no completed study located reports pregnancy outcomes for it (source 15).

Where these compounds sit in our catalog

Frequently asked questions

Sources

1. ClinicalTrials.gov. NCT07629401, Pre-approval Expanded Access of Retatrutide (LY3437943), Eli Lilly and Company, study type EXPANDED_ACCESS, status AVAILABLE, last update posted 6 August 2026. https://clinicaltrials.gov/study/NCT07629401
2. FDA. FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss, content current as of 09/01/2026, retrieved 4 September 2026. https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss
3. ClinicalTrials.gov. NCT04881760, retatrutide phase 2 obesity trial: eligibility criteria, baseline characteristics module and adverse-events module. https://clinicaltrials.gov/study/NCT04881760
4. ClinicalTrials.gov. NCT05611957, A Study of LY3437943 in Healthy Participants and Participants With Impaired Renal Function, phase 1, eligibility criteria. https://clinicaltrials.gov/study/NCT05611957
5. ClinicalTrials.gov. Nine Lilly retatrutide records screened live on 4 September 2026 for reproductive criteria: NCT04867785 (source 6), NCT05929066, NCT05929079, NCT05931367, NCT05936151, NCT06859268, NCT06313528, NCT06383390, NCT07232719. https://clinicaltrials.gov/search?term=retatrutide
6. ClinicalTrials.gov. NCT04867785, retatrutide phase 2 type 2 diabetes trial: baseline characteristics module and adverse-events module. https://clinicaltrials.gov/study/NCT04867785
7. Tucker JAL et al. Nutr Rev. 2025. Meta-analysis of energy intake across the menstrual cycle. PMID 39008822. https://pubmed.ncbi.nlm.nih.gov/39008822/
8. Eli Lilly. MOUNJARO (tirzepatide) prescribing information, sections 7.2, 8.1, 8.2, 8.3 and 17. DailyMed set id d2d7da5d-ad07-4228-955f-cf7e355c8cc0, retrieved 4 September 2026. https://dailymed.nlm.nih.gov
9. Eli Lilly. ZEPBOUND (tirzepatide) prescribing information, sections 8.1, 8.3, 12.3 and Highlights. DailyMed set id 487cd7e7-434c-4925-99fa-aa80b1cc776b and accessdata.fda.gov 217806Orig1s020lbl.pdf, revised 02/2025, retrieved 4 September 2026. https://dailymed.nlm.nih.gov
10. Novo Nordisk. OZEMPIC (semaglutide) prescribing information, sections 8.2, 8.3 and 12.3. DailyMed set id adec4fd2-6858-4c99-91d4-531f5f2a2d79, retrieved 4 September 2026. https://dailymed.nlm.nih.gov
11. Internal analysis of a public Reddit archive: 108 unique posts from 12 subreddits, created 6 August 2025 to 31 August 2026, post ids re-fetched from the Arctic Shift archive API on 4 September 2026.
12. N Engl J Med. 2023. Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial. PMID 37366315. https://pubmed.ncbi.nlm.nih.gov/37366315/
13. Lancet. 2023. Retatrutide phase 2 trial in type 2 diabetes. PMID 37385280. https://pubmed.ncbi.nlm.nih.gov/37385280/
14. Nat Med. 2024. Retatrutide phase 2a MASLD substudy. PMID 38858523, PMC11271400. https://pubmed.ncbi.nlm.nih.gov/38858523/
15. PubMed, ClinicalTrials.gov and openFDA searches on retatrutide reproductive outcomes, posted results and marketing status, run 4 September 2026 (search strings quoted in the text). https://pubmed.ncbi.nlm.nih.gov
16. Dalvit SP. Am J Clin Nutr. 1981. Menstrual cycle and food intake. PMID 7282607. https://pubmed.ncbi.nlm.nih.gov/7282607/
17. Lyons PM et al. Am J Clin Nutr. 1989. Energy intake across the menstrual cycle. PMID 2729155. https://pubmed.ncbi.nlm.nih.gov/2729155/
18. Barr SI et al. Am J Clin Nutr. 1995. Energy intake in the luteal and follicular phases. PMID 7825535. https://pubmed.ncbi.nlm.nih.gov/7825535/
19. Applebey SV et al. Diabetes Obes Metab. 2026. Estrous-cycle timing of GLP-1 receptor agonist administration in female rats. PMID 41017581. https://pubmed.ncbi.nlm.nih.gov/41017581/
20. PubMed and ClinicalTrials.gov searches for cycle-phase-stratified appetite, energy intake or weight outcomes on GLP-1, GIP or glucagon receptor agonists, run 4 September 2026 (search strings quoted in the text). https://clinicaltrials.gov
21. Sehgal NKR et al. Self-reported side effects of semaglutide and tirzepatide in online communities. medRxiv preprint, DOI 10.64898/2026.03.12.26348253, posted 13 March 2026; peer-reviewed version Nature Health, DOI 10.1038/s44360-026-00108-y, 10 April 2026, vol 1 issue 8 pp 806-811, no PubMed identifier as of 4 September 2026. https://doi.org/10.64898/2026.03.12.26348253
22. Frey C et al. Obstet Gynecol. 2026. Menstrual adverse-event signals for GLP-1 receptor agonists in FAERS. PMID 42424619. https://pubmed.ncbi.nlm.nih.gov/42424619/
23. Hudanich M et al. Cureus. 2025. Scoping review of GLP-1 receptor agonists in PCOS. PMID 41141001, PMC12551431. https://pubmed.ncbi.nlm.nih.gov/41141001/
24. Forslund M et al. Eur J Endocrinol. 2026. Systematic review and meta-analysis of GLP-1 receptor agonists in PCOS, Prospero CRD42024535096. PMID 41701618. https://pubmed.ncbi.nlm.nih.gov/41701618/
25. ClinicalTrials.gov. NCT07326111, phase 4 trial in overweight or obesity-related PCOS, lead sponsor University of Bonn, 198 participants estimated, recruiting, no results posted. https://clinicaltrials.gov/study/NCT07326111
26. Skelley JW et al. J Am Pharm Assoc. 2024. Review of GLP-1 receptor agonists and hormonal contraception. PMID 37940101. https://pubmed.ncbi.nlm.nih.gov/37940101/
27. PubMed and ClinicalTrials.gov searches for a standalone publication of the tirzepatide oral contraceptive pharmacokinetic trial, run 4 September 2026 (search strings quoted in the text). https://pubmed.ncbi.nlm.nih.gov
28. Gelfand ST et al. Obes Pillars. 2026. Narrative review of GLP-1 agonists and sexual desire. PMID 41404471, PMC12704374. https://pubmed.ncbi.nlm.nih.gov/41404471/
29. Novo Nordisk. WEGOVY (semaglutide) prescribing information, sections 8.1 and 8.3. DailyMed set id ee06186f-2aa3-4990-a760-757579d8f77b, retrieved 4 September 2026. https://dailymed.nlm.nih.gov
30. Cesta CE et al. JAMA Intern Med. 2024. Second-line diabetes treatments in early pregnancy and major congenital malformations. PMID 38079178. https://pubmed.ncbi.nlm.nih.gov/38079178/
31. Dao K et al. BMJ Open. 2024. First-trimester GLP-1 receptor agonist exposure, prospective multicentre cohort. PMID 38663923. https://pubmed.ncbi.nlm.nih.gov/38663923/
32. Liu X et al. Endocr Connect. 2026. Meta-analysis of GLP-1 receptor agonist exposure and major congenital malformations. PMID 42447044. https://pubmed.ncbi.nlm.nih.gov/42447044/
33. Brown JP et al. Ann Intern Med. 2026. Target trial emulation of GLP-1 receptor agonist continuation in pregnancy, primary funding source National Institutes of Health. PMID 42258827. https://pubmed.ncbi.nlm.nih.gov/42258827/
34. DailyMed. Retatrutide SPL listings, spls.json drug_name=retatrutide, ten entries published 17 November 2025, labeler GUANGZHOU YIXIN CROSS-BORDER E-COMMERCE CO., LTD., approval code C73590 "Export only", refetched 4 September 2026. https://dailymed.nlm.nih.gov

Research use only. Retatrutide, tirzepatide, semaglutide and cagrilintide are referenced here for their published research record. Products sold on this site are supplied for laboratory research, not for human or animal administration, and not as medicines. Nothing in this article is contraception, conception, pregnancy, breastfeeding or dosing guidance, and nothing here claims that any product is safe, unsafe or without effect on any reproductive outcome.