GLP-1 and Fertility UK — What You Need to Know About Mounjaro, Pregnancy and Conception (2026)

This is one of the most important topics for women of reproductive age on GLP-1 medication — and one of the most under-discussed in prescribing consultations. GLP-1 medications both improve fertility and must be stopped before pregnancy. Understanding both sides of this is essential for any woman of childbearing age taking these medications.

Why GLP-1 Medications Can Increase Fertility

Women with obesity, PCOS, or insulin resistance often have disrupted reproductive hormones — particularly:

• Elevated androgens suppressing normal ovulation
• Insulin resistance disrupting the LH surge that triggers ovulation
• Irregular or absent menstrual cycles
• Reduced egg quality from metabolic inflammation

GLP-1 medications address the underlying metabolic drivers of these disruptions. As weight decreases and insulin sensitivity improves, menstrual cycles often normalise. Women who have had very irregular periods — and therefore considered their fertility unreliable — may become unexpectedly fertile. The fertility improvement in PCOS specifically is discussed in detail in GLP-1 for PCOS UK.

Why GLP-1 Medications Must Be Stopped Before Conception

GLP-1 medications are contraindicated during pregnancy based on:

• Animal data: Tirzepatide and semaglutide caused skeletal malformations and reduced foetal weight in animal studies at doses relevant to human exposure
• Absence of human safety data: There are no adequately powered human trials of GLP-1 medications during pregnancy — the drugs are simply too new
• Weight loss is inappropriate during pregnancy: GLP-1-driven calorie restriction would compromise maternal and foetal nutrition during a period of increased nutritional demand
• Regulatory position: The MHRA (UK medicines regulator) recommends against use during pregnancy

When to Stop — The Official Timeline

Most clinicians recommend 2-3 months as a precautionary buffer, even though the pharmacokinetic half-life of these drugs is much shorter. This gives time for the drug to clear completely and for any temporary hormonal effects to stabilise before conception.

If You Become Pregnant While on GLP-1

If you discover you are pregnant while taking a GLP-1 medication:

1. Stop the medication immediately
2. Contact your GP or midwife promptly to inform them
3. Do not panic — the risk from inadvertent early exposure is uncertain but likely low
4. Arrange an early booking appointment and ultrasound
5. Inform your prescribing GP or private clinic so the exposure is documented

There is no evidence that short inadvertent early exposure causes definite harm — but the precautionary principle applies, and stopping immediately is the correct action.

Oral Contraceptives and GLP-1 — The Specific Risk

As discussed in GLP-1 medication interactions, oral contraceptives are affected by GLP-1-induced slowed gastric emptying. The peak absorption of oral contraceptive hormones may be reduced, potentially compromising contraceptive efficacy — particularly in the first weeks of GLP-1 treatment and after dose increases.

The most reliable contraception options while on GLP-1 medication:

• Intrauterine device (IUD/coil): Most reliable — unaffected by GLP-1’s effects on gastric absorption
• Implant (Nexplanon): Subdermal — absorption completely unaffected by GLP-1
• Injectable (Depo-Provera): Injected, not oral — absorption unaffected
• Condoms + oral pill: Double method if oral pill is preferred
• Oral pill with adjusted timing: Some guidance suggests taking the pill at least 1 hour before the GLP-1 injection — discuss with your GP

Planning a Pregnancy After GLP-1 — Optimising Your Position

The period on GLP-1 medication can be used to optimise your reproductive health before conception:

• Lose weight to a BMI closer to the healthy range — improves conception rates, reduces pregnancy complications, and reduces miscarriage risk
• Improve metabolic markers (HbA1c, blood pressure, lipids) — all affect pregnancy outcomes
• Restore regular menstrual cycles if they were disrupted — confirms ovulation is occurring
• Start folate supplementation (400mcg daily) at least 3 months before attempting conception
• Discuss with your GP what a healthy maintenance weight target looks like before stopping medication

Fertility Treatments and GLP-1

For women undergoing IVF or other fertility treatments, the relationship between GLP-1 medication and treatment timing needs individual clinical assessment. Some fertility clinics actively encourage weight loss (sometimes using GLP-1 medication) before starting IVF, as the evidence shows improved IVF outcomes with weight loss in women with obesity. The medication must then be stopped well before the IVF treatment cycle begins. Discuss the exact timing with both your fertility clinic and your GLP-1 prescriber.

Some links in this post are affiliate links. If you purchase through them, I may earn a small commission at no extra cost to you. I only recommend products I use myself. Use code ALAN10 for 10% off Lily & Loaf. This post is for informational purposes only — always consult your GP for medical advice.

Male Fertility and GLP-1 — What We Know

The fertility question is predominantly discussed in the context of women. For men: GLP-1 medications have been associated with improvements in testosterone levels in men with obesity-related hypogonadism — weight loss reliably improves testosterone, regardless of the method. No significant negative effects on male fertility have been demonstrated in clinical trials, though data is limited.

Men taking GLP-1 medication do not have the same urgent contraception considerations as women, but should still be aware that improved testosterone and fertility may be an outcome of significant weight loss — relevant for men who have been trying to conceive without success.

Sources: Corona et al., 2023: GLP-1 medications and male hypogonadism  ·  MHRA: tirzepatide reproductive safety summary  ·  ESHRE 2023 guidelines: obesity and male reproductive health