Written and Medically reviewed by Dr Karen Joash, Consultant Obstetrician and Gynaecologist | Last reviewed: August 2026
The short answer
GLP-1 and dual GIP/GLP-1 medicines can produce substantial weight loss and improve glucose control for eligible patients, but they are prescription medicines, not wellness supplements. They should not be used during pregnancy, while trying to conceive or when breastfeeding. Women using them need specific contraception advice, and everyone losing weight rapidly should protect protein intake, hydration and muscle.
What are GLP-1 medicines?
Medicines such as semaglutide, liraglutide and tirzepatide affect appetite, fullness and glucose regulation. Licensed indications and NHS access criteria differ by product. They should be prescribed after assessment and obtained from a regulated provider.
Common adverse effects include nausea, vomiting, diarrhoea, constipation and abdominal discomfort. Severe persistent abdominal pain, repeated vomiting, dehydration or signs of an allergic reaction need urgent medical advice.
Pregnancy and trying to conceive
Doctors advise not to use GLP-1 medicines during pregnancy, while trying to become pregnant or when breastfeeding. If pregnancy occurs, contact a healthcare professional promptly and stop the medicine as advised.
Current MHRA guidance specifies a washout time before trying to conceive: at least two months for semaglutide and at least one month for tirzepatide. Liraglutide should be stopped just before trying. Always check the latest product-specific advice with the prescriber.
Tirzepatide and the contraceptive pill
Tirzepatide may reduce the effectiveness of oral contraception around treatment initiation and dose increases. MHRA guidance advises adding a barrier method or switching to a non-oral method for four weeks after starting and for four weeks after each dose increase.
This does not mean all GLP-1 medicines affect contraception in exactly the same way. Ask the prescriber or a contraception specialist about your specific product and method.
What changes around menopause?
A woman may be both menopausal and clinically eligible for obesity or diabetes treatment. The medication does not treat hot flushes, vaginal symptoms or other effects of low oestrogen, and HRT does not replace obesity treatment. Care should consider blood pressure, glucose, lipids, sleep, bone health and medicines together.
If you use oral HRT and have persistent vomiting or diarrhoea, ask whether absorption or symptom control needs review. Do not change prescribed HRT without advice. You can also consider non-oral forms of HRT to ensure stability through use of GLP-1 medicines.
How to protect nutrition and muscle
Reduced appetite can make it harder to eat enough protein and micronutrient-rich food. Plan small meals around protein, vegetables or fruit, whole-food carbohydrates and fluids. A dietitian can help if intake becomes very restricted.
Use progressive resistance training at least twice weekly if medically appropriate. Rapid weight loss can include lean tissue as well as fat; training and adequate protein are practical protective measures, not guarantees.
Adequate muscle ensures that your metabolism and health are optimised and all nutritional strategies should address this.
Avoid the supplement trap
No over-the-counter 'GLP-1 booster' has been shown to reproduce prescription-drug effects. Be cautious with products that claim to replace medication, intensify appetite suppression or detox side effects. Review all supplements with the prescriber, especially if eating less or experiencing vomiting.
Frequently asked questions
Can GLP-1 medicines improve fertility?
Weight and metabolic changes may restore ovulation in some people, but these medicines are not fertility treatments and must be stopped before pregnancy.
Can I take Mounjaro with the pill?
You need additional or alternative contraception for four weeks after starting tirzepatide and after each dose increase, according to MHRA guidance.
What if I am too nauseated to eat?
Contact the prescriber. Dose, hydration and treatment may need review; persistent vomiting is not something to manage with supplements alone.
A PurerVita note
PurerVita supports evidence-led choices across women's hormonal, metabolic and reproductive health. Supplements can complement food and clinical care; they do not diagnose or treat medical conditions. Seek personalised advice for symptoms, pregnancy plans, medicines or abnormal test results.
Explore PurerVita's evidence-led support for women's health.
Sources
- MHRA: GLP-1 medicines — what you need to know
- MHRA: Contraception and pregnancy warning
- NHS: Strength and flexibility