What to Know Before Taking Obesity Drugs While on Birth Control

Some GLP-1 drugs, like Mounjaro, may have a negative impact on those taking birth control pills.

People taking oral contraceptives and a GLP-1 receptor, particularly Mounjaro, may want to reconsider their birth control methods.

These drugs can interfere with the absorption of birth control pills and how effective they are at protecting a person from pregnancy.

“Mounjaro is the only GLP-1 that carries a warning on its label to use backup contraception upon starting Mounjaro or upon increasing the dose to avoid any possible changes in the efficacy of oral birth control pills due to delayed stomach emptying,” Rekha Kumar, MD, practicing endocrinologist in NYC and Chief Medical Officer of Found, told Health.

Here’s why GLP-1 drugs may affect the effectiveness of oral contraceptives, how the drugs interact with other forms of birth control, and what certain people need to consider when taking contraceptives and GLP-1 drugs.

GLP-1 Drugs and the Effectiveness of Oral Contraceptives

The concern surrounding oral contraception and GLP-1 is not harm, it's effectiveness.

All GLP-1 medicines including Ozempic, Wegovy, and Mounjaro delay stomach emptying. This means anything consumed stays in the stomach longer than usual.

“Due to delayed gastric emptying, the absorption of medications can be impacted with all of these medicines,” Kumar said.

The package insert for Mounjaro cites a study that found a 20% reduction in the overall exposure of combined oral contraceptive with ethinyl estradiol and norgestimate, observed following the administration of a single 5 mg dose of tirzepatide (Mounjaro).

The study was conducted at a point where the effect on gastric emptying was maximal, namely following a single 5 mg dose.

Other GLP-1s like liraglutide (Victoza), semaglutide (Ozempic), and dulaglutide (Trulicity) were tested with oral contraceptives and did not have a clinically meaningful impact on the absorption and kinetics of oral contraceptives, Diana Isaacs, PharmD, the co-director of endocrine disorders in pregnancy at Cleveland Clinic Endocrinology and Metabolism Institute, told Health.

“As far as we know, the interaction is only with tirzepatide,” she said. “It could be related to the fact that tirzepatide is a dual incretin agonist impacting GLP-1 and GIP [gastric inhibitory peptide], and may have an additional impact on absorption.”

Gastrointestinal side effects of GLP-1s, such as nausea and vomiting, can also play a part.

“If someone vomits after taking an oral contraceptive, that will impact its effectiveness,” said Isaacs.

How Other Forms of Contraception Interact With GLP-1 Drugs

The package insert for Mounjaro advises females using oral contraceptives to switch to a non-oral contraceptive method or add a barrier method of contraception for four weeks after initiation and for four weeks after each dose escalation.

“[There] must be caution exercised for the actual contraceptive effect in those four weeks after initiation and dose escalation as noted,” Karl Nadolsky, DO, an endocrinologist and diplomate at the American Board of Obesity Medicine, told Health.

When taking Mounjaro, people usually start at 2.5 mg weekly for four weeks and then increase to 5 mg weekly, which is considered the initial therapeutic dose.

“On a practical level, this would mean having a backup [contraception] for at least eight weeks and possibly longer if the person will be titrating to a higher dose since Mounjaro can go up to 15 mg weekly with 2.5 mg dose escalations every four weeks,” said Isaacs.

She noted that it doesn’t hurt to use a backup method of birth control that does not rely on oral absorption.

“There are many to choose from such as barrier methods; IUD, NuvaRing, arm implant, or injection,” Isaacs said.

The Mounjaro package states that non-hormonal contraceptives should not be affected by the drug, so women using alternative forms of birth control don’t need to be concerned about decreased effectiveness.

For People With PCOS Who Are Taking GLP-1 Drugs

According to Kumar, GLP-1s are becoming used more frequently in the management of polycystic ovarian syndrome (PCOS), a condition that causes a hormonal imbalance and metabolism problems.

The hormonal imbalance caused by PCOS affects the ovaries to the point where a woman’s eggs might not develop appropriately or might not be released during ovulation. Both of these can affect the ability to conceive.

A review that looked at GLP-1s in the treatment of obesity in PCOS found that the medications “are significantly more effective than metformin in reducing BMI, waist circumference, and insulin resistance in patients with PCOS, however, they are more likely to be associated with some adverse reactions as headache and nausea.”

For women who have PCOS and who take GLP-1s, Kumar said it’s important to consider contraception.

“When metabolic health and insulin resistance are treated well with GLP-1s, women who previously did not ovulate, might have a more regular cycle and become more fertile,” said Kumar.

While this may mean certain health obstacles have been overcome, it also means the potential for an unplanned pregnancy has increased.

GLP-1 Drugs Are Not Safe During Pregnancy

Nadolsky stressed that all weight-reducing medications should not be taken during pregnancy to avoid active weight loss during fetal development.

Currently, there is not enough research that has been done on humans taking GLP-1s during pregnancy or while breastfeeding, and doctors recommend discontinuing these medications while pregnant or breastfeeding.

Mounjaro’s insert cites animal studies on rats and rabbits, which suggest possible fetal harm with exposure to tirzepatide.

“But it should be noted that poorly controlled diabetes mellitus results in definitively known maternal and fetal risks,” said Nadolsky, “so [the insert] mentions that tirzepatide, ‘should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.’”

If you are taking a GLP-1 drug and are pregnant or trying to become pregnant, speak to a healthcare provider immediately.