Can you take weight loss pills while trying to conceive? This is a question many people ask when hoping to improve their health before pregnancy. Whilst achieving a healthy weight before conception is associated with better fertility outcomes and reduced pregnancy complications, weight loss medications — including GLP-1 receptor agonists, tirzepatide, naltrexone/bupropion, and orlistat — are not recommended when actively trying to get pregnant. NHS and MHRA guidance is clear: most require a washout period before attempting conception. This article explains why, outlines safer alternatives, and advises when to seek support from your GP.

Weight Loss Pills and Fertility: What You Need to Know

Weight loss medications are not recommended when trying to conceive, as many carry known or theoretical risks to a developing embryo and have not been adequately studied in women attempting pregnancy.

If you are trying to conceive, it is entirely natural to want to be in the best possible health beforehand. Achieving a healthy weight before pregnancy is associated with improved fertility outcomes, reduced risk of miscarriage, and lower rates of complications such as gestational diabetes and pre-eclampsia. However, the question of whether weight loss pills are safe to use whilst actively trying to get pregnant is an important one that deserves careful consideration.

The short answer, supported by NHS and MHRA guidance, is that weight loss medications — including GLP-1 receptor agonists (such as semaglutide and liraglutide), tirzepatide, naltrexone/bupropion, and orlistat — are not recommended when you are trying to conceive. Many of these medicines have not been adequately studied in women who are attempting pregnancy, and some carry known or theoretical risks to a developing embryo, even in the very earliest stages before a pregnancy is confirmed. Because conception can occur at any point during a menstrual cycle, continued use of these medications whilst trying to conceive creates a window of potential exposure.

It is also worth noting that some weight loss medicines — for example, naltrexone/bupropion — may affect hormonal and neurochemical pathways, and that any significant caloric restriction associated with treatment can disrupt menstrual regularity. Before starting, continuing, or stopping any weight loss medication, it is strongly advisable to speak with your GP or a healthcare professional who can assess your individual circumstances.

If you are using any anti-obesity medicine and are sexually active without reliable contraception, you should use effective contraception throughout treatment and until the recommended washout period before planned conception is complete. If you think you may be pregnant, stop the medication and contact your GP promptly. Suspected side effects from any medicine or supplement can be reported to the MHRA via the Yellow Card scheme (yellowcard.mhra.gov.uk).

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Which Weight Loss Medications Are Not Recommended When Trying to Conceive

All UK-licensed weight loss medicines — including semaglutide, liraglutide, tirzepatide, naltrexone/bupropion, and orlistat — are not recommended when trying to conceive, each requiring discontinuation before planned pregnancy.

Several weight loss medications are currently available in the UK, either on prescription or via regulated online pharmacies, and each carries specific safety considerations for those trying to conceive.

GLP-1 receptor agonists

Semaglutide (Wegovy) Semaglutide works by mimicking the hormone GLP-1, regulating appetite and slowing gastric emptying. The UK Summary of Product Characteristics (SmPC) advises that semaglutide should be discontinued at least two months before attempting conception. Animal studies have shown potential embryotoxic effects, and although human data are limited, the precautionary principle applies. Women who become pregnant unexpectedly whilst taking semaglutide should stop immediately and contact their GP.

Liraglutide (Saxenda) Liraglutide acts via the same mechanism as semaglutide. The UK SmPC advises that liraglutide should be avoided in pregnancy and discontinued when pregnancy is planned. Unlike semaglutide, no specific two-month washout period is defined in the UK SmPC for liraglutide; your GP or pharmacist can advise on the appropriate timing based on your individual circumstances.

Tirzepatide (Mounjaro) Tirzepatide is a dual GIP/GLP-1 receptor agonist licensed in the UK for weight management. The UK SmPC advises that tirzepatide should be discontinued at least one month before a planned pregnancy, owing to its long half-life. It should not be used during pregnancy.

Naltrexone/bupropion (Mysimba) This combination medicine is licensed in the UK as an adjunct to diet and exercise for weight management. It is not recommended during pregnancy and should be discontinued before attempting conception. Effective contraception should be used throughout treatment. Women who become pregnant whilst taking Mysimba should stop immediately and seek medical advice.

Orlistat (Xenical, Alli) Orlistat works by inhibiting pancreatic lipase, reducing dietary fat absorption by approximately 30%. Whilst it is not known to be directly teratogenic, its mechanism raises concern: reduced fat absorption can impair uptake of fat-soluble vitamins A, D, E, and K, as well as beta-carotene. Given the limited pregnancy safety data, orlistat is not recommended when trying to conceive. Women taking orlistat should discuss stopping it with their GP before attempting pregnancy.

Over-the-counter and herbal supplements Many products marketed for weight loss — including those containing caffeine, green tea extract, glucomannan, or various herbal blends — are not regulated as medicines in the same way as prescription products. Their safety during conception attempts or early pregnancy is largely unknown. Some herbal ingredients have uterine-stimulant properties or may interact with other medications; certain green tea extracts have been associated with hepatotoxicity. The NHS advises caution with all unlicensed supplements during this period.

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Illegal and dangerous slimming products The MHRA has issued warnings about illegal 'fat-burner' products, including those containing 2,4-dinitrophenol (DNP), which is not approved for human consumption and has caused deaths. These products should never be used. If you have purchased weight loss products online or from unregulated sources, seek advice from your GP or pharmacist before taking them.

In summary, no weight loss medicine currently available in the UK is recommended for use when actively trying to conceive, and most should be stopped in advance of attempting pregnancy, with the specific timing depending on the individual medicine. Always seek guidance from your GP or pharmacist.

NHS-Recommended Ways to Manage Weight Before Pregnancy

NICE-supported approaches including a balanced diet, at least 150 minutes of moderate exercise weekly, and NHS Tier 2 weight management programmes are the recommended safe alternatives to medication before conception.

There are well-evidenced, safe approaches to managing weight before pregnancy that do not carry the risks associated with pharmacological interventions. NICE guidance (PH27: Weight management before, during and after pregnancy; CG189: Obesity — identification, assessment and management; and PH53: Weight management lifestyle services) supports a structured approach that prioritises sustainable lifestyle change.

Dietary modification A balanced, nutrient-rich diet is the cornerstone of healthy pre-conception weight management. The NHS Eatwell Guide provides a practical framework, emphasising:

• Plenty of fruit, vegetables, and wholegrains

• Lean proteins and oily fish (in moderation)

• Reduced intake of ultra-processed foods, added sugars, and saturated fats

• Adequate hydration

Crash diets or very low-calorie regimens are not recommended when trying to conceive, as they may disrupt menstrual regularity and deplete essential micronutrients.

Physical activity The UK Chief Medical Officers' guidelines recommend at least 150 minutes of moderate-intensity activity per week for adults, alongside muscle-strengthening activities on at least two days per week. Regular exercise supports weight management, improves insulin sensitivity, and may positively influence ovulatory function — particularly in women with polycystic ovary syndrome (PCOS). Activities such as brisk walking, swimming, and cycling are well-tolerated and appropriate during the pre-conception period.

Structured weight management programmes For those with a BMI of 30 or above (or 25 or above with relevant comorbidities in some areas), GPs can refer patients to NHS-commissioned weight management services, including Tier 2 behavioural programmes. These offer dietitian support, behavioural coaching, and group or individual sessions — all without the need for medication. Eligibility criteria vary by locality; your GP can advise on local provision.

Folic acid and micronutrient support Regardless of weight, all women trying to conceive are advised to take 400 micrograms of folic acid daily, starting before conception and continuing until 12 weeks of pregnancy, as recommended by NICE and the NHS. Women with a BMI of 30 kg/m² or above, or other higher-risk factors (such as a personal or family history of neural tube defects, or use of certain medicines), are advised to take 5 mg of folic acid daily — this higher dose is available on prescription from your GP.

Vitamin D supplementation of 10 micrograms (400 IU) daily is recommended for all adults in the UK during autumn and winter, and year-round for those at risk of deficiency (including those with limited sun exposure). This recommendation continues throughout pregnancy and breastfeeding. Your GP can advise whether you need additional supplementation.

When to Speak to Your GP or a Fertility Specialist

Speak to your GP if you are taking any prescription weight loss medication and planning a pregnancy, have been trying to conceive for 12 months without success, or have a BMI over 30 affecting fertility.

Navigating weight management whilst trying to conceive can feel complex, and it is important to know when professional guidance is essential rather than optional. Your GP is the most appropriate first point of contact and can provide personalised advice based on your medical history, current medications, and fertility goals.

You should speak to your GP if:

• You are currently taking any prescription weight loss medication (such as semaglutide, liraglutide, tirzepatide, naltrexone/bupropion, or orlistat) and are planning to try for a baby

• You have been trying to conceive for 12 months without success (or 6 months if you are over 35), or sooner if you have known risk factors such as irregular or absent periods, suspected tubal disease, severe endometriosis, or a history of pelvic surgery or sexually transmitted infection

• You have a BMI over 30 and are concerned about how this may affect your fertility or pregnancy

• You have a condition such as PCOS, hypothyroidism, or type 2 diabetes that may interact with both weight and fertility

• You have taken weight loss medication and have recently discovered you are pregnant

• You are using anti-obesity medicines and are not using reliable contraception

Your GP can review your current medications, advise on an appropriate washout period before conception, and refer you to specialist services if needed. It is important to note that fertility assessment should consider both partners — NICE guidance (CG156: Fertility problems — assessment and treatment) recommends that both partners are assessed when there is difficulty conceiving. In some cases, referral to a fertility specialist or consultant in reproductive medicine may be appropriate — particularly where weight-related hormonal disruption is suspected as a contributing factor.

It is also worth noting that unexplained weight gain or difficulty losing weight despite lifestyle changes may itself be a sign of an underlying condition such as hypothyroidism or insulin resistance, both of which can impair fertility. These are diagnosable and treatable, and early investigation can make a meaningful difference.

Ultimately, the pre-conception period is a valuable opportunity to optimise your health in a safe, evidence-based way. With the right support, it is entirely possible to achieve meaningful weight management without relying on medications that carry uncertainty during this sensitive time. If you experience any suspected side effects from a medicine or supplement, report these to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

Frequently Asked Questions