Does Wegovy, Mounjaro, or Ozempic Affect Birth Control?

Weight loss is one of the most common health goals, yet achieving and maintaining it can often feel like a challenge. In recent years, weight loss injections such as Wegovy, Mounjaro and Ozempic have provided a breakthrough option, offering effective support where diet and exercise alone may not be enough. The treatments, known as GLP-1 receptor agonists, have transformed weight management for many people. 

Understanding how these treatments interact with oral contraceptives, emergency contraception, and fertility is vital if you’re trying to avoid pregnancy or plan another one in the near future. This blog guides you through the precautions around weight-loss injections and contraception, and explains when switching methods may be advisable.

Does semaglutide affect birth control?

Wegovy and Ozempic contain semaglutide, a GLP-1 receptor agonist that slows the emptying of the stomach. As a result, food and medicines, including the contraceptive pill, may take longer to move through the digestive system, which in theory could delay or reduce the absorption of oral hormones.

However, clinical evidence suggests that semaglutide does not significantly affect the effectiveness of combined oral contraceptives. Some show no reduction in the bioavailability of ethinylestradiol or levonorgestrel, the two hormones in many combined pills, when taken alongside semaglutide. 

What about side effects?

Semaglutide is commonly associated with nausea, vomiting, and diarrhoea, particularly in the early stages of treatment. If you vomit within three hours of taking your pill, or experience diarrhoea lasting more than 24 hours, the pill may not be absorbed properly.

In these cases, follow your missed pill instructions or use a backup method like condoms until you have taken seven consecutive pills without stomach upset.

Does Mounjaro affect birth control?

Unlike semaglutide, Mounjaro contains tirzepatide, which acts on two gut hormones, GLP-1 and GIP, making it a dual agonist. This dual mechanism enhances weight loss but has more profound effects on gastric emptying.

Clinical studies indicate that tirzepatide can reduce the bioavailability of oral hormonal contraceptives by around 20%. This means there is a real risk of reduced pill effectiveness, especially during:

• The first four weeks after starting Mounjaro
• The first four weeks after any dose increase

Guideline advice:
Use backup contraception, such as condoms, or switch to non-oral methods like:

• Intrauterine devices (IUDs)
• Contraceptive implants
• Vaginal rings
• Contraceptive injections
• Patches

Failing to use additional protection during these periods may increase the risk of unplanned pregnancy. Regulatory bodies, including the MHRA and FDA, have issued advisories on this.

Can semaglutide or tirzepatide be used in pregnancy?

Both semaglutide (Wegovy/Ozempic) and tirzepatide (Mounjaro) should not be used during pregnancy. These drugs haven’t been adequately studied in pregnant humans, but animal studies show potential risks, including:

• Embryo loss
• Fetal growth restriction
• Skeletal abnormalities

Guidance for pregnancy planning:

• Stop Wegovy/Ozempic: At least 2 months before trying to conceive.
• Stop Mounjaro: At least 1 month before conception, due to its prolonged half-life.

If you become pregnant while on these medications, stop treatment immediately and consult your healthcare professional.

Can Wegovy affect the contraceptive pill?

Although Wegovy can delay gastric emptying, clinical trials show no significant reduction in contraceptive hormone absorption.
However, if you frequently experience nausea or diarrhoea on Wegovy, the pill could become less reliable. In such cases:

• Use backup contraception during prolonged gastrointestinal upset
• Consider switching to a non-oral method if symptoms persist

Should I switch to a different contraceptive?

For most people on Wegovy or Ozempic, switching contraceptive methods is not necessary unless you have persistent digestive side effects.
For those on Mounjaro, however, it is highly recommended to:

• Use non-oral contraception where possible
• Use condoms for at least four weeks after starting or increasing your dose

Our pharmacists at Batley Pharmacy can help you assess the best option for your circumstances.

Can I use emergency contraception on Wegovy?

There is no strong evidence to suggest Wegovy or Ozempic affects the efficacy of emergency contraception.
However, if vomiting or diarrhoea occurs within a few hours of taking an emergency pill, it may not work effectively. In these cases:

• A copper IUD is the most reliable form of emergency contraception
• Discuss your options with a healthcare professional promptly

Can I get pregnant while on Wegovy?

Yes, it’s possible to become pregnant on Wegovy, especially if:

• You rely on oral contraception and have persistent vomiting or diarrhoea
• You lose significant weight, which can restore fertility, particularly in women with PCOS

Conclusion

• Wegovy and Ozempic: Generally safe with oral contraceptives, but monitor for gastrointestinal issues.
• Mounjaro: Can reduce pill effectiveness by up to 20%, use alternative or additional contraception.
• Pregnancy planning: Stop GLP-1 or dual agonists well before conception.
• Improved fertility: Be aware that weight loss itself can make pregnancy more likely.

At Batley Pharmacy, our clinicians can guide you through safe, effective weight-loss treatment while ensuring your contraception remains reliable. Book a private consultation today to discuss your options.

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