Does Mounjaro affect the coil? What you need to know about tirzepatide and IUDs

You've just been prescribed Mounjaro and you have a coil (here's what actually applies to you

A question our prescribers hear most weeks: "I have the Mirena) do I need to do anything different?" It is a completely reasonable thing to ask, and the answer is reassuring. The clinical concern about Mounjaro's interaction with hormonal contraception is rooted in how tirzepatide slows gastric emptying. When digestion is delayed, an oral pill that relies on absorption through the gut may not reach its usual plasma concentration, which is why NHS England advises adding a non-oral method for the first four weeks of tirzepatide treatment and for four weeks after every dose increase, if you are on the pill.

Intrauterine devices work in an entirely different way. A hormonal coil like the Mirena releases levonorgestrel directly into the lining of the womb; it does not pass through your digestive tract at all. A copper coil uses no hormones whatsoever. Neither type depends on gut absorption, which means the gastric-emptying effect that concerns prescribers with oral pills simply does not apply. If you want to explore the pill interaction in more detail, our page on Mounjaro and the pill covers the mechanism thoroughly.

This distinction is confirmed by NHS England's guidance on weight-management injections, which singles out oral contraceptives as the category needing an additional method during tirzepatide treatment. Coils are not mentioned, because there is no equivalent evidence of reduced effectiveness. That does not mean contraception is irrelevant when you start Mounjaro, it means the coil is already one of the more reliable choices to be using alongside it.

The pregnancy warning still applies, regardless of contraceptive method

Even though the coil is not affected by tirzepatide's mechanism, it is worth being clear about one thing: Mounjaro is not recommended during pregnancy, while breastfeeding, or when actively trying to conceive. The medicine has not been adequately studied in these situations, and the standard clinical advice is to stop treatment before attempting conception, observing a wash-out period your prescriber will specify.

This matters for coil users in a practical sense. If your coil expires and you decide not to replace it, or if it is removed for any reason, talk to your prescriber before doing so. Similarly, if you ever have any reason to suspect the coil has failed (which is rare but not impossible) take a pregnancy test and contact your clinical team promptly. Tirzepatide is a prescription medicine reviewed by a real clinician before every repeat order, which means any change to your circumstances, including a change to your contraception, is something your prescriber needs to know about.

If you are also using HRT alongside tirzepatide, there is a separate but related consideration around transdermal versus oral forms, our page on Mounjaro and HRT explains what NHS England recommends there. And for a broader look at how tirzepatide works as a medicine, our tirzepatide overview is a good starting point.

What the Mirena coil specifically, and what about longer-term coil users?

The Mirena is the most commonly used hormonal coil in the UK, and it comes up by name in many of the questions we receive. Because it is a long-acting reversible contraceptive that typically lasts five to eight years depending on individual clinical factors, many people starting Mounjaro will already have one in place. There is no clinical reason to remove or replace the Mirena because you are starting tirzepatide. The local hormonal effect remains unaffected.

If you want the specific evidence base around the Mirena and tirzepatide, our dedicated Mirena and Mounjaro page goes into more detail. For a broader picture of the coil and tirzepatide together, including what to tell your GP and what questions to raise at your next contraceptive review, this page on Mounjaro and the coil covers the clinical landscape from all angles.

One thing worth raising with your GP is that starting a weight-loss medicine is a reasonable prompt to review your contraception generally, not because tirzepatide changes the coil's effectiveness, but because a significant change to your health and your body over the coming months is always a good backdrop for checking everything is still the right fit. The NHS England guidance on weight-management injections addresses contraception considerations and is worth reading if you want the full official picture.

Reporting unexpected changes and staying safe on treatment

If you are on Mounjaro and notice anything unexpected (whether that relates to your contraception, your cycle, your skin, or anything else) the right step is to speak to your prescriber or GP. Changes in body weight can sometimes affect hormone levels and cycle patterns independently of the medicine itself, so distinguishing between the effects of tirzepatide and the effects of meaningful weight change is not always straightforward.

Side effects worth knowing about include the common gastrointestinal symptoms (nausea, loose stools, indigestion, constipation and fatigue are the most frequently reported), typically most noticeable after a dose increase and settling over days to weeks for most people. For side effects that extend to skin changes, our page on Mounjaro and breakouts addresses a question we see come up a lot. For changes affecting vision, our page on Mounjaro and the eyes covers what the evidence says. Suspected side effects can also be reported directly to the MHRA via the Yellow Card scheme, which the regulator uses to monitor medicines once they are in widespread use.

If you are weighing up whether Mounjaro is the right option for you (including how private treatment is priced and what a full-service prescription actually includes) our Mounjaro price comparison page sets out the honest picture. When you are ready to take the next step, check your eligibility with our prescribers, consultations are free and reviewed the same day by a GPhC-registered Independent Prescriber.