Is there a retatrutide study on oral contraceptives?

Yes. ClinicalTrials.gov record NCT06039826 describes a phase 1 study of retatrutide with a pill containing ethinyl estradiol and drospirenone. It enrolled 46 postmenopausal women and finished in July 2024. No results were posted as of October 5, 2026.

Do IUDs, implants or injections interact with retatrutide?

No retatrutide data exist for these methods. The tirzepatide label says hormonal contraceptives that are not taken by mouth should not be affected, because the concern is absorption from the gut. That statement is about tirzepatide, and it is an inference when applied to retatrutide.

Why would a weight-loss injection change how a pill works?

These drugs slow the rate at which the stomach empties. A pill then reaches the gut later, which can lower and delay its peak level in the blood. With a single 5 mg dose of tirzepatide, peak ethinyl estradiol fell by 59% and total exposure fell by 20%.

Does semaglutide carry the same birth control warning as tirzepatide?

No. The Ozempic label reports no clinically relevant interaction with an ethinylestradiol and levonorgestrel pill at the 1 mg dose. The Ozempic and Wegovy labels do not advise a backup contraceptive method.

Does Retatrutide Make Birth Control Pills Less Effective?

Q: How long does the tirzepatide label say to use a backup method?

The Zepbound and Mounjaro labels advise a non-oral method or an added barrier method for 4 weeks after starting and for 4 weeks after each dose increase. No such period has been set for retatrutide. Retatrutide has no FDA label.

The short answer: Nobody can say yet, because the one study that tested it has not reported results. Eli Lilly completed a phase 1 study of retatrutide with a combined birth control pill in July 2024. As of October 2026, no results are posted or published. The related drug tirzepatide lowers pill absorption enough that its FDA label advises a backup method, so the same caution is reasonable for retatrutide.

Has retatrutide been tested with birth control pills?

Yes. A dedicated study exists, but its results are not public.

The ClinicalTrials.gov record NCT06039826 describes a phase 1 study of retatrutide (listed under its code name, LY3437943) with a combined oral contraceptive. The pill contained ethinyl estradiol and drospirenone. The study measured blood levels of both hormones with and without retatrutide. Its primary outcomes were the total exposure (AUC), the peak level (Cmax) and the time to peak (Tmax) of each hormone.

The record gives these facts:

46 participants enrolled.
All were postmenopausal women with a body mass index of 27.0 to 40.0.
The study started on September 12, 2023, and finished on July 11, 2024.
Each participant was in the study for up to about 29 weeks.

When we checked on October 5, 2026, the record showed no posted results. A PubMed search for retatrutide with "contraceptive", "ethinyl" or "drospirenone" returned no papers. So the data exist inside Lilly, and the public cannot see them yet.

One design point matters. The study used postmenopausal women, which is common for this kind of test. It measured hormone levels in the blood. It did not measure ovulation or pregnancy rates.

What is known about retatrutide and stomach emptying?

This part is retatrutide data. A 2023 paper by Lilly scientists in Diabetes, Obesity and Metabolism is titled "The novel GIP, GLP-1 and glucagon receptor agonist retatrutide delays gastric emptying." The PubMed record has no abstract, and the publisher page blocked our access. We cite the finding in the title and give no numbers from it.

Slower stomach emptying matters because a pill must leave the stomach before the gut can absorb it. A delay can lower or postpone the peak level of a drug taken by mouth.

Two more retatrutide facts are relevant. In a phase 1b trial in the Lancet, stomach and gut problems were the most frequently reported side effects, and the half-life of retatrutide was about 6 days. Our side effects guide covers nausea, vomiting and diarrhea in more detail.

Lilly also ran a separate interaction study, NCT05445232, in 32 participants. It tested retatrutide with oral midazolam, warfarin and caffeine to look at drug-metabolizing enzymes. It finished in February 2023, and its record shows no posted results either. It did not include a contraceptive.

What does the tirzepatide label say about the pill?

Everything in this section is tirzepatide data, not retatrutide data. Tirzepatide is the closest approved relative. Lilly makes both drugs, and both act on the GIP and GLP-1 receptors.

The Zepbound label on DailyMed (revised August 2026) says use "may reduce the efficacy of oral hormonal contraceptives due to delayed gastric emptying." The Mounjaro label says the same. Both labels report one interaction study. Participants took a combined pill (0.035 mg ethinyl estradiol and 0.25 mg norgestimate) with a single 5 mg dose of tirzepatide. The results were:

Peak levels of ethinyl estradiol, norgestimate and norelgestromin fell by 59%, 66% and 55%.
Total exposure (AUC) fell by 20%, 21% and 23%.
The peak arrived 2.5 to 4.5 hours later.

The labels advise patients on oral hormonal contraceptives to switch to a non-oral method, or to add a barrier method. This applies for 4 weeks after starting and for 4 weeks after each dose increase. The labels explain why the window is limited: the delay in stomach emptying "is largest after the first dose and diminishes over time." They also say hormonal contraceptives that are not taken by mouth "should not be affected."

The labels describe hormone levels. They do not report pregnancy rates in pill users. The sibling site mounjaro.md covers tirzepatide in more depth.

What do the semaglutide labels say?

Semaglutide points the other way, which shows why one drug cannot stand in for another. This is semaglutide data, not retatrutide data.

The Ozempic label says semaglutide delays stomach emptying and may affect oral medications. It then reports that trials at the 1 mg dose found "no clinically relevant drug-drug interaction" with the medications tested. Those included an oral contraceptive with ethinylestradiol and levonorgestrel. The Wegovy label (revised June 2026) lists ethinyl estradiol and levonorgestrel among drugs with "no clinically significant differences" in blood levels. Neither label advises a backup contraceptive method.

A 2025 review of GLP-1 drug interactions reached the same split. It found most stomach-emptying interactions "clinically insignificant", but noted significant exposure changes for oral contraceptives with tirzepatide. The sibling post on Ozempic and birth control covers semaglutide in full.

Can those findings be applied to retatrutide?

Only as an inference. Here is the reasoning, and its limits.

Reasons to expect an effect like the one seen with tirzepatide:

Retatrutide delays stomach emptying, according to the 2023 paper above.
Retatrutide shares two of its three receptor targets with tirzepatide.
Lilly judged the question important enough to run a dedicated pill study.

Reasons the answer could differ:

Retatrutide also activates the glucagon receptor, which tirzepatide does not. Our comparison of the two drugs explains the difference.
Semaglutide also delays stomach emptying, yet its labels report no meaningful change in pill hormone levels. A shared mechanism does not guarantee a shared result.
The size of the delay, and how fast it fades with repeat doses, is not public for retatrutide.

So no source can state that retatrutide makes the pill less effective. No source can state that it does not. Retatrutide has no FDA label, so it has no official contraception advice.

What do the retatrutide trials require for contraception?

The phase 2 obesity trial, NCT04881760, excluded women of childbearing potential who were not using an "adequate contraceptive method." The public record does not say which methods counted. The public eligibility lists for the phase 3 TRIUMPH-1 trial do not mention contraception. Full protocols often hold more detail than the registry page.

People in a retatrutide trial should follow the contraception rules in their consent form and ask the study team which methods are accepted. Pregnancy itself is a separate topic. See our post on retatrutide during pregnancy or while trying to conceive.

The bottom line

Retatrutide has been tested with a combined birth control pill, but the results are not public as of October 2026. The drug is reported to delay stomach emptying. Its close relative tirzepatide lowers pill hormone levels enough that the FDA label advises a non-oral or barrier method for 4 weeks after starting and after each dose increase. Semaglutide labels carry no such advice. Until Lilly reports the retatrutide data, the cautious reading is to treat the pill as possibly less reliable and to discuss a non-oral or backup method with a clinician.

Last updated: October 2026. This article is for informational purposes only and does not constitute medical advice. Retatrutide is investigational and not FDA approved. Talk with your clinician or study team before you change any contraceptive method.