12/5/2026

Contraceptives and weight loss medications: How Wegovy and Mounjaro can affect the efficacy of birth control pills

When treating with weight loss medications like Wegovy (semaglutide) and Mounjaro (tirzepatide), it is important to consider how the medications can affect fertility and the efficacy of contraceptives. Medications such as semaglutide (Ozempic, Wegovy, Rybelsus) and tirzepatide (Mounjaro) can contribute to improved fertility in women with obesity, partly as a result of weight loss and improved hormonal and metabolic function. At the same time, they can affect the absorption and efficacy of oral contraceptives.

Angelica Brandelius

MD, PhD, Certified Fitness & Medical Trainer

Illustration of a stylized human head with flowers and vines growing from the top, accompanied by the title 'A Lighter and Healthier UK' and the subtitle 'An Important Document on Morbid Obesity'.

Open PDF

How do GLP-1 and GIP medications affect the efficacy of birth control pills?

GLP-1 and GIP receptor agonists are medications that mimic the body's own hormones for satiety and blood sugar regulation. By activating these hormone systems, the medications affect, among other things, appetite regulation, insulin release, and the stomach's emptying rate. An important part of the mechanism of action is that gastric emptying is delayed, which contributes to a longer feeling of fullness and reduced energy intake.

This effect can simultaneously affect how the body absorbs medications taken by mouth. Oral medications, such as birth control pills, need to pass through the stomach and be absorbed in the small intestine to achieve the correct concentration in the blood. When gastric emptying is slower, the absorption of certain medications may change.

The effect appears to be particularly relevant in treatment with tirzepatide (Mounjaro), where it has been shown that exposure to oral contraceptives can decrease, primarily at the start of treatment and upon dose increases of Mounjaro.

Weight loss and improved metabolic health during treatment can simultaneously contribute to improved fertility in certain individuals. This means that the likelihood of pregnancy may increase during treatment.

For individuals using oral contraceptives, it is therefore important to discuss prevention with the treating physician before treatment begins. In some cases, supplementary or alternative contraceptive methods may be recommended, especially during periods of dose escalation.

Mounjaro and birth control pills: Which recommendations apply?

Individuals using birth control pills are recommended to either switch to a non-oral contraceptive or use a barrier method, such as a condom, during the first four weeks after starting treatment with Mounjaro (tirzepatide) and for four weeks after each dose increase.

The background is that tirzepatide delays gastric emptying, which can affect the absorption of medications taken by mouth, including oral hormonal contraceptives.

Do side effects from Wegovy and Ozempic affect the efficacy of birth control pills?

In the event of side effects such as vomiting or severe diarrhea, which can occur during treatment with Wegovy or Ozempic, the absorption of oral contraceptives may be temporarily impaired. In these situations, the recommendations in the package leaflet for the specific contraceptive should be followed. Often, this means that supplementary protection, such as a condom, is recommended for a limited period.

Birth control pills contain hormones such as estrogen and progestogen and are dependent on stable absorption via the gastrointestinal tract to provide reliable pregnancy protection.

Pregnancy planning during medical weight loss

Treatment with medications for weight loss should be discontinued before pregnancy, as safety during use in pregnancy has not been sufficiently studied. The recommended washout period varies between different medications depending on how long the substance remains in the body.

Generally, the following is recommended:

Semaglutide (Wegovy, Ozempic, Rybelsus): treatment should be discontinued at least 2 months before planned pregnancy, according to the product information.
Tirzepatide (Mounjaro): treatment should be discontinued at least 1 month before planned pregnancy.

During this period, it is important to use a reliable contraceptive.

Weight loss and improved metabolic health can contribute to improved fertility and more regular ovulation, for example, in conditions like PCOS. This also means that the possibility of becoming pregnant may increase during treatment, making contraceptive counseling extra important.

Safe and continuous follow-up at Yazen

At Yazen, every patient undergoes an individual medical assessment where licensed physicians take the entire medication list into account, including contraceptives, before treatment is initiated.

Treatment is followed up continuously by a multidisciplinary team consisting primarily of your doctor and coach, as well as other healthcare professionals as needed. The follow-up is adapted based on the patient's individual needs and includes, among other things, efficacy, side effects, and potential drug interactions.