Everything You Need to Know About Weight-Loss Drugs and Birth Control

In case you missed the latest chapter in the story of weight-loss medications going mainstream, these days, everyone’s talking about #OzempicBabies.

Over the past year-plus, people using prescription weight-loss medications—not just Ozempic but other popular injectable GLP-1 agonists—have taken to social media to share stories of unexpectedly becoming pregnant, often following years of infertility struggles, or even while taking birth control pills. As more stories went viral, the media went so far as to declare an Ozempic Baby Boom. While the idea that the popularity of weight-loss drugs is leading to a major increase in fertility has yet to be confirmed by data, it turns out that there are a few critical things any woman of childbearing age should know when taking GLP-1 meds—and the word hasn’t necessarily gotten out about all of them.

Example: The U.K. equivalent of the FDA recently put out an alert letting women know that some popular weight-loss medications may cause oral contraceptives to fail, while also posing potential risks to unborn babies. The former isn’t actually breaking news; the fact that certain weight-loss drugs may prevent oral contraceptives from working properly is spelled out right on the packaging insert. Yet with many people buying off-brand, compounded weight loss drugs, often without adequate oversight by a medical provider, many women remain unaware of this risk.

The details to know: The weight-loss treatment tirzepatide (including the brand-name drugs Zepbound and Mounjaro) can interfere with the absorption of oral birth control, in part because it makes the stomach empty much more slowly. This has been shown to reduce the concentration of contraceptives in the bloodstream by up to 20 percent. Therefore, both the drug manufacturers and doctors advise that anyone using oral contraceptives should add condoms as a backup method for at least four weeks after starting tirzepatide injections, or after any dose increase (the risk decreases outside that one-month window). Another option is to switch to a non-oral birth control method, like an IUD, implant, or ring, all of which are unaffected by tirzepatide.

As for other popular GLP-1s like semaglutide (including brand name medications Ozempic and Wegovy) and liraglutide (Saxenda), they affect gastric enzymes slightly differently than tirzepatide does. Based on clinical studies to date, there is no evidence that semaglutides compromise the effectiveness of oral contraceptives, and some health organizations like Planned Parenthood maintain that they’re safe to use with the pill. However, doctors report seeing real-world cases of breakthrough bleeding and unintended pregnancy associated with all GLP-1 weight-loss injections, and prefer that women play it safe and use backup condoms or non-oral contraceptives.