Weight Loss Injections Could Weaken Birth Control, Warn UK Regulators

Popular weight loss injections like Ozempic, Wegovy, and Mounjaro have raised safety concerns among UK regulators. The Medicines and Healthcare products Regulatory Agency (MHRA) recently issued a warning that these drugs could make contraception less effective and pose risks to unborn babies.

Women using any slimming injections are urged to use reliable birth control. The MHRA specifically advises those on Mounjaro to use additional contraception methods if taking the Pill, as the drug may reduce its effectiveness, especially in overweight women.

Safe sex is crucial during the first four weeks after starting Mounjaro or after dose increases. Women who become pregnant while using these drugs should stop immediately. Breastfeeding mothers are also advised to cease use due to unknown risks to infants.

Since the drugs entered wider use, the MHRA has recorded over 40 pregnancy-related reports linked to these medications, including birth defects, miscarriages, and unintended pregnancies. Twenty-six of these involve Mounjaro, with one unintended pregnancy reported.

Eight reports relate to semaglutide (the active ingredient in Ozempic and Wegovy). Mounjaro and similar drugs work by suppressing appetite through hormone changes but can interfere with digestion, potentially flushing out contraceptive pills and reducing their effectiveness.

About 35,000 women of childbearing age were prescribed these injections on the NHS in England in 2024, but the actual number is likely higher due to private purchases. The MHRA also warns against buying these medicines from unregulated sources like beauty salons or social media.

The warning follows reports of unplanned pregnancies on Ozempic, Wegovy, and Mounjaro despite contraception.

Dr. Alison Cave of the MHRA stresses that these drugs are medical treatments, not cosmetic quick fixes, and patients should always follow professional guidance and read medication leaflets. Experts agree that these drugs may slow stomach emptying, reducing oral contraceptive absorption, although more research is needed.

Given the unclear risks to pregnancy and evidence that other weight loss methods can increase miscarriage chances, women are advised to take extra precautions to avoid pregnancy.

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Deb Oliviara revealed she got pregnant on Ozempic and stopped it as soon as she knew.

Reports from women using these drugs confirm unexpected pregnancies, sometimes linked to increased fertility after weight loss, but in some cases due to reduced contraceptive effectiveness. One woman in the US shared how semaglutide made birth control less effective while also boosting fertility, prompting her to stop the drug once she became pregnant.

These weight loss injections belong to the GLP-1 receptor agonist class, which mimics natural fullness hormones. Mounjaro also affects a second hormone related to appetite and blood sugar.

The MHRA tracks side effects through its Yellow Card scheme, which monitors drug safety in the UK. This system was established after the 1960s thalidomide scandal and helps detect adverse reactions, leading to warnings or drug withdrawals if necessary.

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To sum up, women using weight loss injections must take effective contraception to prevent pregnancy. If pregnancy occurs, they should stop the medication right away.

It’s also important to avoid unregulated or unofficial products, as these could pose serious health risks. While these injections can be valuable for managing weight, they come with potential side effects and risks that require close attention and responsible use to ensure safety.

Implications of Hormonal Interactions

Dr. Jennifer Gunter, a well-known gynecologist and author, emphasizes the importance of understanding how medications like Mounjaro may interact with hormonal contraceptives. She states, 'Weight loss medications can potentially alter the efficiency of hormonal birth control due to changes in metabolism and absorption rates.' This crucial insight underlines the need for women to consult healthcare providers when considering weight loss injections.

Using dual contraceptive methods, such as condoms alongside hormonal birth control, can mitigate risks of unintended pregnancies. This strategy is recommended by health professionals to maintain reproductive autonomy while pursuing weight loss goals.

Experts from the National Health Service (NHS) have highlighted that patients should be educated about the potential interactions between weight loss drugs and birth control. Dr. Alice Roberts, an advocate for patient education, notes, 'Informed decisions can significantly reduce health risks.'

Healthcare providers should offer comprehensive counseling, discussing the necessity of additional contraceptive methods for patients on Mounjaro or similar medications. This proactive approach not only empowers patients but also reinforces their understanding of how weight loss therapies can impact overall health.

Clinical Perspective & Next Steps

The intersection of weight loss injections and contraception highlights the importance of informed healthcare decisions. As experts agree, dual contraceptive methods can provide a safety net for those using medications like Mounjaro. By prioritizing education and open discussions with healthcare providers, women can navigate these complexities more effectively.

Utilizing resources from trusted professionals, such as Mayo Clinic, can further enhance understanding and management of these medications. Ultimately, informed choices lead to better health outcomes and reproductive safety.