Semaglutide warnings: the side effects and safety signals that matter

Step 1: understand what the common side effects actually feel like

Before worrying about the rare but serious warnings, it helps to know what ordinary semaglutide side effects look like, because most people experience at least some of them, and most of the time they are manageable rather than dangerous. The GI profile is well-documented: nausea tends to arrive in the first few days after a new or increased dose, sometimes with loose stools, burping, or a general feeling of queasiness. You can read a fuller breakdown of what semaglutide side effects involve in practice, including why they concentrate around dose changes. The short version is that gastric emptying slows significantly, which is part of how the medicine suppresses appetite, and also why your stomach takes time to adjust. For most patients, symptoms peak in the first week and ease off considerably by week two. Staying hydrated, eating smaller portions and avoiding heavy or fatty meals during this settling-in period tends to reduce the impact. That said, if vomiting or diarrhoea is severe enough that you cannot keep fluids down for more than 24 hours, that is a clinical conversation, not something to sit out at home, and our guidance on what to do when semaglutide makes you feel sick covers the practical steps to take before that point is reached. Dehydration from prolonged GI illness can put pressure on the kidneys, and the NHS highlights this as a reason to seek advice promptly rather than waiting.

Step 2: recognise the symptoms that need urgent medical attention

Some semaglutide warnings are not about discomfort, they are about genuine safety. The most important ones to memorise before starting treatment are as follows. Severe, persistent stomach pain that radiates toward the back, with or without vomiting, may indicate acute pancreatitis. In January 2026, the MHRA issued a Drug Safety Update for GLP-1 medicines specifically to reinforce this: pancreatitis is infrequent but can be serious, and anyone experiencing those symptoms should stop the injection and seek urgent medical help. Gallbladder problems are a second flagged risk, pain in the upper right abdomen, sometimes with fever or jaundice, warrants the same urgency. A serious allergic reaction (swelling of the face or throat, difficulty breathing, rapid pulse) is rare but requires emergency attention. The NHS semaglutide medicines page lists these clearly and is worth bookmarking alongside your prescription information. Finally, if you notice sudden changes in vision, tell your GP without delay, this is particularly relevant for people with pre-existing diabetic eye disease, and our page covering the Wegovy warnings patients most commonly ask about explains how to tell which symptoms warrant same-day contact with a clinician. It is a good idea to keep the patient information leaflet from your pen somewhere accessible, because the full list of signs and what to do about each one is printed there.

Step 3: know the specific patient groups for whom Wegovy carries additional cautions

Some Wegovy warnings apply to the whole population on the medicine; others are specific to particular situations. Semaglutide is not recommended during pregnancy, while breastfeeding, or if you are actively trying to conceive, the medicine should be stopped before attempting conception, and your prescriber will advise on the appropriate washout period. It is also not licensed for use in under-18s. A personal or family history of medullary thyroid carcinoma, or a condition called MEN2 (multiple endocrine neoplasia type 2), is a contraindication. If you have a history of pancreatitis or certain gastrointestinal conditions, that needs to be discussed before starting. It is also worth noting that oral contraceptives may be less reliably absorbed during early treatment with tirzepatide, for semaglutide the evidence base is less clear-cut, but discussing contraception with your prescriber as part of the consultation is sensible practice. For anyone considering treatment, our Wegovy overview page sets out the full eligibility picture, and the starting point for any of this is a clinical assessment. On the question of whether Wegovy side effects improve over time, the pattern for most patients is that they do, but that picture is individual, and your prescriber is the right person to track it with you.

Step 4: use the reporting system and know where to get support

The Yellow Card scheme exists precisely because real-world safety data matters. If you experience a side effect you are not sure about (or one that seems more severe than expected) you can report it directly to the MHRA at yellowcard.mhra.gov.uk, and you do not need to wait for a GP appointment to do so. Clinicians file their own reports separately; patient reports add a layer of signal the regulators actively want. One thing our prescribers hear fairly regularly is that patients waited longer than they should have before flagging a symptom, partly because they did not want to seem like they were overreacting. That caution is understandable, but a quick message to your clinical team costs nothing. For context on the broader cost of treatment and what clinical support is typically included, the Wegovy pricing page explains what a private prescription should cover, aftercare access being part of what distinguishes a well-run service from a dispensing-only arrangement. Our contact page has details of how to reach the aftercare team seven days a week if a question comes up between consultations. The MHRA's guidance on GLP-1 medicines, published on GOV.UK, also provides a plain-language summary of the benefit-risk picture for patients considering or already on treatment.