Who shouldn't take semaglutide — and what to check before you start

You've been offered Wegovy, but something in your history is giving you pause

That instinct to double-check is worth acting on. Semaglutide works by activating GLP-1 receptors, which slows gastric emptying and reduces appetite, but those same pathways interact with conditions and medicines in ways a prescriber needs to map before treatment starts. The Wegovy overview on our site sets out the licensed indication; this page focuses on the side that doesn't get enough attention: who should stay off it entirely, and who needs a careful conversation first.

The clearest cases are the absolute contraindications. A personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia type 2 (MEN2) puts semaglutide firmly off the table. Animal studies flagged a thyroid C-cell signal, and although causation in humans hasn't been established, regulators took a precautionary position in the licence. No amount of weight-related benefit changes that calculation. The NHS medicines page for semaglutide lists this alongside the other situations where it must not be used, worth scanning for yourself in under a minute if you want the plain-language version directly from the NHS.

A history of pancreatitis sits in a different category: not always an absolute bar, but always a reason for a detailed prescriber discussion. In January 2026 the MHRA issued a Drug Safety Update confirming acute pancreatitis as a known, infrequent but serious risk across GLP-1 medicines. Anyone whose pancreas has already been inflamed once is at higher baseline risk, and the prescriber needs to weigh that individually.

Pregnancy, conception and contraception: what the guidance actually says

This is the area where the most confusion sits, partly because the guidance has sharpened over time. The position now is unambiguous: semaglutide is not recommended during pregnancy, while breastfeeding, or if you are actively trying to conceive. It's also not a matter of missing a dose, there is a washout period the MHRA advises before attempting conception, meaning treatment needs to be stopped with enough lead time. Your prescriber will tell you the specific window.

Oral contraceptives add another layer. The NHS England guidance on weight-management injections explains that tirzepatide specifically requires an additional non-oral contraceptive method during the first four weeks and after each dose increase, because gastric slowing can reduce pill absorption. For semaglutide, the evidence of that effect is less established, but the broader recommendation to use reliable contraception throughout treatment remains in place. If you're on the pill, flag it at consultation; your prescriber will give you specific advice rather than a blanket instruction.

The under-18 rule is absolute. Wegovy carries no paediatric licence in the UK, full stop. Parents sometimes ask on behalf of teenagers with significant obesity, the honest answer is that this isn't a clinical judgement call, it's a licensing boundary. If you're wondering whether semaglutide is the right option for you as an adult, that's a separate and more nuanced question, but age below 18 closes it immediately.

Conditions that call for caution rather than a flat no

Beyond the absolute contraindications, a range of conditions shift the risk-benefit picture enough that treatment requires extra clinical scrutiny rather than blanket exclusion. These include:

Severe gastrointestinal conditions. Gastroparesis (where the stomach already empties slowly) is a significant concern, since semaglutide slows emptying further. Inflammatory bowel disease in a flare, or a history of serious GI surgery, also warrants careful prescriber assessment. The problem isn't necessarily that treatment is impossible; it's that the GI side-effect profile overlaps with symptoms of the underlying condition, making monitoring harder.

Diabetic retinopathy. People with type 2 diabetes and existing retinopathy should be aware that rapid improvements in blood glucose have been linked to transient worsening of eye changes. Your prescriber will want to know your retinopathy status before proceeding.

Kidney and liver function. Severe dehydration from GI side effects can put stress on kidneys that are already compromised. Anyone with significant renal impairment needs that factored into the decision. Hepatic impairment also features in the SmPC's caution list.

Specific medicines. Semaglutide doesn't have a long list of direct pharmacokinetic drug interactions, but the slowed gastric emptying affects how other oral medicines are absorbed. If you take thyroid medication, blood pressure tablets or anything else in the morning, ask whether the timing needs adjusting. Our page on taking ibuprofen alongside semaglutide covers one common example. Mental health history, particularly a history of eating disorders, also warrants a careful conversation, not a refusal, but an informed one.

What this means in practice at the point of prescription

None of this is listed to discourage you. It's listed because a prescriber who asks about your thyroid history, your family history, your current medicines and your reproductive plans isn't being difficult; they're doing exactly what the licence and their professional standards require. A quick prescription with no questions asked would be the worrying sign, not the reassuring one.

At nume, a GPhC-registered Independent Prescriber personally reviews every consultation the same day, not software, not a questionnaire scored by an algorithm. The safety infrastructure exists so that the conditions above get caught before a pen is dispatched, not discovered afterwards. If you'd like to understand how the dosing schedule works once you're cleared to start, that's the natural next question. If something in this page has flagged a doubt, the place to bring it is the consultation itself, not a forum, not this article.

Privately prescribed Wegovy sits at a price point that some people find a stretch; you can review what's included and what the typical cost of Wegovy looks like before you book anything. The consultation itself is free, and there's no obligation to proceed.

If you're ready to see whether treatment is appropriate for your circumstances, check your eligibility with our prescribers, the clinical team, details of which are on our clinical team page, reviews consultations seven days a week.