Safe to take, and safe to start.

Who should not take them

Mounjaro (tirzepatide), Wegovy and the Wegovy Pill (semaglutide) are licensed for weight loss in adults with a BMI of 30 or more, or 27 or more with a weight-related condition, alongside diet and activity. The MHRA says they should not be used for cosmetic weight loss.

They must not be used if you have had an allergic reaction to the medicine or any of its ingredients. That is the only formal contraindication in the product information. They also should not be used:

• during pregnancy, or while trying to get pregnant
• while breastfeeding (see below)
• together with another GLP-1 medicine, such as Ozempic or Saxenda

Some people can't be treated through an online service even if the medicine might suit them, because they need care in person. Our eligibility guide lists who can and can't be treated by PPRX.

Conditions to tell the prescriber about

These don't always rule treatment out, but the product information says they need caution, closer monitoring, or a change to other medicines. Tell the prescriber if you have:

• had pancreatitis. Neither medicine has been studied in people with a history of pancreatitis.
• type 2 diabetes treated with insulin or a sulfonylurea such as gliclazide. The risk of low blood sugar goes up, and those doses may need lowering.
• diabetic retinopathy (diabetes-related eye disease). Rapid improvement in blood sugar has been linked to a temporary worsening.
• a severe stomach or bowel condition, including severe gastroparesis (very slow stomach emptying)
• kidney problems. Vomiting and diarrhoea can cause dehydration, which can make kidney function worse.
• severe liver disease or very severe heart failure. There is little or no experience of these medicines in those groups.
• an eating disorder now or in the past (see below)
• an operation or procedure coming up (see below)

Pregnancy, breastfeeding and contraception

Don't use these medicines while pregnant or trying to get pregnant. If you could get pregnant, use contraception throughout treatment. Stop Mounjaro at least one month before trying to conceive, and Wegovy or the Wegovy Pill at least two months before, because they stay in the body for a long time. If you become pregnant while taking one, stop and tell your prescriber.

Mounjaro and the contraceptive pill: Mounjaro may make the pill less effective in people who are overweight. If you take the pill, the MHRA advises either switching to a non-oral method, such as the coil or implant, or also using a barrier method such as condoms for four weeks after starting Mounjaro and for four weeks after each dose increase.

Wegovy, the Wegovy Pill and the contraceptive pill: in studies, semaglutide did not reduce the pill's effect to a degree that matters, so no extra method is needed for that reason.

Breastfeeding: the MHRA and the NHS advise against using these medicines while breastfeeding, and Wegovy's product information says it should not be used. Mounjaro's product information, based on a study of 11 women, says it could be considered during breastfeeding. Weight-loss treatment can usually wait, and we don't prescribe these medicines online while you're breastfeeding.

Our side-effects guide covers fertility in more detail.

Serious side effects that need urgent help

Most side effects are mild stomach upsets that settle. Our side-effects guide covers those and how to manage them. A few are serious. Stop the medicine and get help (call 111, or 999 in an emergency) if you have:

• Severe stomach pain that doesn't go away, which may spread to your back. This can be acute pancreatitis. If pancreatitis is confirmed, the medicine should not be restarted.
• Severe pain in your tummy that could be your gallbladder. Gallstones and inflammation of the gallbladder are listed side effects.
• Signs of dehydration that don't improve after vomiting or diarrhoea, such as dark yellow pee or peeing less than normal, or dizziness when you stand that doesn't go away. Dehydration can harm the kidneys, and older people are more at risk. Keep drinking fluids if you are being sick. Call 999 if someone is confused or very hard to wake.
• A serious allergic reaction, such as swelling of the face, lips, tongue or throat, or difficulty breathing. Anaphylaxis has been reported with both medicines. Call 999.
• Low blood sugar (shaking, sweating, confusion) if you also take insulin or a sulfonylurea.
• A sudden loss of sight, or eyesight that gets worse quickly, on Wegovy or the Wegovy Pill. A rare eye condition called NAION has been linked to semaglutide. Contact a doctor urgently, or go to A&E if you can't reach one.

Other medicines

Tell the prescriber about everything you take, including medicines bought without a prescription. The main points from the product information:

• These medicines slow the emptying of the stomach, which can change how quickly some tablets are absorbed. With Mounjaro this is most noticeable when you start and after each dose increase.
• Warfarin and similar blood thinners: your INR may need checking more often when you start.
• Medicines where small changes in level matter, such as digoxin, may need monitoring when you start Mounjaro and after each dose increase.
• Levothyroxine: the Wegovy Pill raised levels of thyroid hormone in a study, so your thyroid levels may need checking.
• The Wegovy Pill must be taken on an empty stomach. Wait 30 minutes after taking it before you take any other tablets.
• Insulin and sulfonylureas: the dose may need lowering to avoid low blood sugar.

Operations and sedation

Before any procedure under general anaesthetic or deep sedation, tell the team, including the anaesthetist, that you take a GLP-1 medicine. Because these medicines slow stomach emptying, food can stay in the stomach despite fasting, which raises the risk of breathing it into the lungs. Don't stop the medicine without talking to your doctor first.

Eating disorders

Weight-loss medicines reduce appetite, so they can do harm to someone with an eating disorder. In its April 2026 review of weight-loss services, the GPhC reported concerns about medicines being supplied to people with a history of eating disorders, and said services must follow the guidance that protects vulnerable people.

We don't prescribe these medicines online to anyone who has, or has had, anorexia or bulimia. Please answer the questions about eating honestly. They are there to keep you safe, not to catch you out.

If you're worried about your eating, the NHS advises seeing a GP as soon as you can. You can also talk in confidence to the eating disorders charity Beat on 0808 801 0677.

What we check

• Every order is reviewed by a UK-registered prescriber before anything is dispensed.
• GPhC guidance says the prescriber must check your weight, height or BMI independently rather than relying on a questionnaire, keep checking how your weight loss is going while you stay on treatment, and ask your consent to tell your GP.
• The prescriber asks about your health, your other medicines and pregnancy, and won't prescribe if the medicine isn't suitable for you.
• If you have a side effect, tell us. We can review your dose, and help you report it to the MHRA through the Yellow Card scheme.
• Tell us straight away if your health changes, you start a new medicine, you're planning a pregnancy or you become pregnant.

How it works explains each step, and our guide to choosing an online pharmacy explains what any safe service should do.