Guides / Safety and status
GLP-1s and birth control: does Mounjaro or Wegovy affect the pill?
The tirzepatide labels carry a warning about the pill. The semaglutide labels don't. It matters most in the first weeks and after each dose increase.
[00] Short answer
- Mounjaro and Zepbound (tirzepatide) may make birth control pills work less well. The US labels say to switch to a non-oral method, or add a barrier method, for 4 weeks after starting and for 4 weeks after each dose increase1–2.
- In a study, one 5 mg dose of tirzepatide cut the peak level of ethinyl estradiol in the blood by 59% and total exposure by 20%1.
- Ozempic and Wegovy (semaglutide) have no such warning. Studies found no clinically relevant change in the pill hormones ethinyl estradiol and levonorgestrel3–4,7.
- The tirzepatide labels say hormonal methods not taken by mouth (such as the implant, hormonal coil, injection, patch or ring) should not be affected1.
- UK: the Mounjaro SmPC gives the same 4-week advice, aimed at women with overweight or obesity. The UK semaglutide SmPCs recommend contraception for women who could get pregnant5–6.
Does Mounjaro or Zepbound make birth control pills less effective?
It may. The Mounjaro and Zepbound labels say tirzepatide "may reduce the efficacy of oral hormonal contraceptives due to delayed gastric emptying", and that this delay "is largest after the first dose and diminishes over time"1–2. Tirzepatide slows how fast your stomach empties, so less of the pill is absorbed in the hours after you take it.
The Zepbound label, word for word1:
"Advise patients using oral hormonal contraceptives to switch to a non-oral contraceptive method, or add a barrier method of contraception for 4 weeks after initiation with ZEPBOUND and for 4 weeks after each dose escalation."
The Mounjaro label says the same thing2. Both add that "hormonal contraceptives that are not administered orally should not be affected"1–2. The patient Medication Guides put it as: "Birth control pills by mouth may not work as well", and your provider "may recommend another type of birth control" for those 4-week windows1–2.
The labels base this on a study of a combined pill (0.035 mg ethinyl estradiol and 0.25 mg norgestimate) taken with one 5 mg dose of tirzepatide. Peak blood levels fell by 59% for ethinyl estradiol, 66% for norgestimate and 55% for norelgestromin. Total exposure fell by 20%, 21% and 23%, and the peak came 2.5 to 4.5 hours later1–2.
What each GLP-1 label says about the pill
Only tirzepatide has a birth control warning. Neither the US nor the UK semaglutide labels ask you to change or add to the pill.
| Medicine | US label | UK SmPC |
|---|---|---|
| Mounjaro (tirzepatide) | Switch to a non-oral method or add a barrier method for 4 weeks after starting and 4 weeks after each dose increase2 | Same 4-week advice, because reduced efficacy "cannot be excluded" in women with obesity or overweight. No change needed with a normal BMI5 |
| Zepbound (tirzepatide) | Same as Mounjaro1 | Not sold in the UK. Tirzepatide is sold as Mounjaro there |
| Wegovy (semaglutide) | No warning. No clinically significant change in ethinyl estradiol or levonorgestrel levels3 | "Not anticipated to decrease the effectiveness" of the pill. Contraception recommended for women who could get pregnant6 |
| Ozempic (semaglutide) | No warning. No clinically relevant interaction at 1 mg, no dose change needed4 | Same wording as Wegovy7 |
A barrier method means condoms or a diaphragm. Non-oral hormonal methods include the implant, hormonal coil, injection, patch and ring.
How long do you need backup contraception on Mounjaro or Zepbound?
The label window is 4 weeks after your first tirzepatide dose and 4 weeks after every dose increase1–2. Tirzepatide starts at 2.5 mg weekly and goes up in 2.5 mg steps after at least 4 weeks on each dose1–2. So if your dose goes up every 4 weeks, the windows join end to end and cover the whole time you're stepping up, plus 4 weeks after your last increase.
| Dose | Earliest start | 4-week window after it |
|---|---|---|
| 2.5 mg | Week 0 (first dose) | Weeks 1 to 4 |
| 5 mg | Week 4 at the earliest | Weeks 5 to 8 |
| 7.5 mg | Week 8 at the earliest | Weeks 9 to 12 |
| 10 mg | Week 12 at the earliest | Weeks 13 to 16 |
| 12.5 mg | Week 16 at the earliest | Weeks 17 to 20 |
| 15 mg | Week 20 at the earliest | Weeks 21 to 24 |
If you stay on a dose longer than 4 weeks, there's a gap with no window until your next increase. Not everyone goes up to 15 mg. Your prescriber sets your steps.
If you stop at 5 mg or 10 mg and stay there, the windows end 4 weeks after your last increase. Put your own dates into the dose schedule planner to see when each increase falls.
Does Ozempic or Wegovy affect birth control?
No effect on the pill was found in studies of semaglutide, and neither US label carries a warning. The Ozempic label says semaglutide 1 mg was tested with an ethinyl estradiol and levonorgestrel pill at steady state, and "no clinically relevant drug-drug interaction" was seen, so "no dose adjustment is required"4. The Wegovy label lists ethinyl estradiol and levonorgestrel among drugs with "no clinically significant differences" when taken with semaglutide3.
The UK SmPCs for Ozempic and Wegovy say semaglutide "is not anticipated to decrease the effectiveness of oral contraceptives". Ethinyl estradiol exposure didn't change, and levonorgestrel exposure went up 20%6–7.
Both US labels still say semaglutide slows stomach emptying and that this may affect how other pills are absorbed3–4. That's a general note, not a birth control rule.
What the UK says: MHRA advice on GLP-1s and contraception
In the UK, the MHRA says anyone who could get pregnant should take steps not to while using a GLP-1, and for a set "wash-out" time after stopping8. For Mounjaro and the pill, it says to add a barrier method such as a condom for 4 weeks after starting and 4 weeks after any dose increase, or switch to a non-oral method like the coil or implant8.
The Mounjaro SmPC explains why. A single 5 mg dose lowered pill hormone levels, but the SmPC says this "is not considered clinically relevant" and no change is needed "in women with normal BMI". There is limited information in women with obesity or overweight, so the 4-week advice applies to them5. The MHRA's June 2025 press release said this advice only applies to Mounjaro, not other GLP-1s9.
The UK Wegovy and Ozempic SmPCs say "women of childbearing potential are recommended to use contraception when treated with semaglutide"6–7. For what the labels say about pregnancy itself, see GLP-1s and pregnancy.
[Tool]Dose schedule plannerYour label dose steps as dates, so you can see each 4-week windowQuestions
Does Mounjaro stop the pill working?
It may make it work less well, mostly in the first weeks. The US label says to switch to a non-oral method or add a barrier method for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase.
Does Zepbound affect birth control?
Yes, the same as Mounjaro, because both are tirzepatide. The Zepbound label gives the same 4-week advice after starting and after each dose increase. Methods not taken by mouth should not be affected.
Does Ozempic or Wegovy affect birth control pills?
Their labels have no birth control warning. Studies found no clinically relevant change in ethinyl estradiol or levonorgestrel levels with semaglutide.
Is the implant or coil affected by Mounjaro?
The Mounjaro and Zepbound labels say hormonal contraceptives that are not taken by mouth should not be affected. The MHRA names the coil and implant as non-oral options.
Do I need backup contraception if I stay on the same Mounjaro dose?
The label windows are 4 weeks after starting and 4 weeks after each dose increase. Once you have been on the same dose for more than 4 weeks, the label gives no extra window. Check with your prescriber or pharmacist.
Is the UK advice different from the US?
The 4-week advice is the same. The UK Mounjaro SmPC says no change is needed for women with a normal BMI and aims the advice at women with overweight or obesity. The MHRA also says to use contraception on any GLP-1.
Sources
Checked against Mounjaro and Zepbound US prescribing information and Medication Guides (08/2026), Wegovy (06/2026) and Ozempic (05/2026) US prescribing information, UK SmPCs for Mounjaro, Wegovy and Ozempic (eMC, 2026), and MHRA GLP-1 guidance (February 2026). How we check
- 1Zepbound (tirzepatide) US prescribing information and Medication Guide, sections 2.1, 7.2, 8.3, 12.3 and 17. Eli Lilly, revised 08/2026
- 2Mounjaro (tirzepatide) US prescribing information and Medication Guide, sections 2.1, 7.2, 8.3, 12.3 and 17. Eli Lilly, revised 08/2026
- 3Wegovy (semaglutide) injection and tablets, US prescribing information, sections 7.2 and 12.3. Novo Nordisk, revised 06/2026
- 4Ozempic (semaglutide) injection, US prescribing information, section 12.3 (Figure 4). Novo Nordisk, revised 05/2026
- 5Mounjaro KwikPen, UK Summary of Product Characteristics, sections 4.5 and 4.6. eMC, updated 8 Sep 2026
- 6Wegovy FlexTouch, UK Summary of Product Characteristics, sections 4.5 and 4.6. eMC, updated 22 Sep 2026
- 7Ozempic, UK Summary of Product Characteristics, sections 4.5 and 4.6. eMC, updated 28 Jul 2026
- 8MHRA: GLP-1 medicines for weight loss and diabetes: what you need to know (GOV.UK). updated 5 Feb 2026; section on contraception and pregnancy
- 9MHRA press release: Women on "skinny jabs" must use effective contraception, MHRA urges in latest guidance. 5 June 2025
This guide explains what labels and published studies say. It isn't medical advice and doesn't replace your prescriber or pharmacist.
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Read next
- GLP-1s and pregnancy: what each label saysNone of these medicines has enough data in pregnancy to know the risk, so the labels lean on animal studies and how long each drug stays in the body.
- Mounjaro vs ZepboundSame medicine, same doses, same pens and vials. The difference is what each one is approved for, and in the UK there's only Mounjaro.
- GLP-1 side effects: how common and how long they lastStomach trouble tops the side-effect list on every GLP-1 label, and most of it happens while the dose is going up.