Does Mounjaro stop the coil from working?

Why would a weight-loss injection affect contraception at all?

Tirzepatide slows gastric emptying, food and medicines that pass through the stomach take longer to move on. For anything absorbed through the gut wall, that delay can alter how much of a substance actually reaches the bloodstream. Oral contraceptive pills depend entirely on gut absorption, which is why NHS England advises women on Mounjaro to use an additional contraceptive method (such as condoms) during the first four weeks of treatment and for four weeks after each dose increase, to account for any reduction in pill absorption.

Intrauterine devices work differently. A copper IUD releases copper ions locally inside the uterus to prevent fertilisation. A hormonal IUS (such as Mirena or Kyleena) releases a small, continuous amount of levonorgestrel directly into the uterine cavity, not into the bloodstream in any significant quantity. Neither device relies on the gut in any way. Slowing gastric emptying simply has nothing to intercept. The coil keeps doing its job regardless of what tirzepatide is doing in your stomach. You can read more about how tirzepatide interacts with different contraceptive methods on our page about Mounjaro and the pill.

The NHS England guidance on weight-management injections specifically names oral contraceptives as the method requiring additional cover, the IUS and IUD are not mentioned because the absorption mechanism that creates the concern simply does not apply to them.

Should coil users do anything differently before starting Mounjaro?

From a contraception standpoint, no additional steps are needed specifically because of the coil. You do not need to switch methods, add a barrier method, or time your treatment around your device. The coil remains effective from day one of Mounjaro and throughout any dose increases.

There are, however, a few broader points worth raising with your prescriber at consultation. Tirzepatide is not recommended during pregnancy, while breastfeeding, or for anyone planning to conceive, so confirming that your current contraception is working as intended matters. The MHRA also advises using reliable contraception throughout treatment and for a wash-out period before trying to conceive, guidance that applies to all users, not just those on the pill. If your coil is approaching its replacement date, it is sensible to discuss timing with your GP or sexual health clinic before starting a new medicine, simply so you have a clear picture of your reproductive health plans.

For a broader look at everything involved in a Mounjaro consultation (eligibility, what the prescriber reviews, the clinical process) our Mounjaro overview covers the full picture.

Does the hormonal IUS raise any separate concerns with tirzepatide?

No interaction between tirzepatide and the hormonal IUS has been identified, and none would be expected given how the device delivers its hormone. The low local dose of levonorgestrel from an IUS is not meaningfully absorbed into the systemic circulation in the way an oral pill dose is, it acts almost entirely at the site of release inside the uterus. There is no shared pharmacological pathway for tirzepatide to disrupt.

It is worth keeping perspective here. Tirzepatide itself can cause gastrointestinal side effects, nausea, loose stools, and indigestion are the most commonly reported, usually most noticeable in the first weeks of treatment or after a dose step. Those symptoms are unrelated to contraceptive efficacy for coil users, though they are worth knowing about before you start. Our dedicated page on Mounjaro and the coil goes into more clinical depth if you want it.

If you are considering Mounjaro and want to understand what private treatment costs and what is included, our Mounjaro price comparison page lays out the honest context, including what a legitimate prescription should always cover. Pricing aside, the first step is always a clinical assessment by a registered prescriber, and you can find out more about the tirzepatide treatment pathway itself before deciding.

When should you raise contraception at your Mounjaro consultation?

Always. Even when the answer turns out to be straightforward (as it is for coil users) your prescriber needs to know which contraceptive method you use. It informs the advice they give about pregnancy planning, the wash-out period if you decide to stop treatment at any point, and whether any other medicines you take alongside your contraception could be affected by tirzepatide. The clinical review at nume (sorry, at a regulated service like ours) is not a form-ticking exercise. A real clinician reads your answers and considers the full picture.

If you are using the pill alongside a coil as dual protection, that is worth flagging explicitly, since the pill component does sit within the category of oral medicines whose absorption can be affected. Similarly, if you are on any other daily oral medicine, raise it: the lisinopril and Mounjaro page is one example of how we look at specific medicines, and the same thinking applies across oral treatments more broadly.

The NHS tirzepatide medicines page is a reliable reference for the full list of side effects and precautions, and a good place to read before your consultation. When you are ready to speak to a prescriber, start your free consultation with our clinical team, there are no hidden fees and the review happens the same day.