Wegovy and Vomiting Blood: What the Symptom Means and When to Get Help

You've just seen blood in your vomit after a Wegovy dose

Stop. This is the situation where context matters enormously, but urgency comes first. If there is a significant amount of blood, if it looks dark red or coffee-ground coloured, or if you feel faint, have severe abdominal pain, or your pulse is racing, call 999. Do not wait to see whether it passes.

Smaller amounts of bright red streaking after repeated, forceful retching are different in character. They may represent a Mallory-Weiss tear, a small split in the lining where the oesophagus meets the stomach, caused by the mechanical force of vomiting hard. This is not unique to Wegovy; it can happen after any bout of severe sickness. But it still needs same-day assessment at an urgent treatment centre or A&E, because only an examination can rule out something more serious.

Either way, stop your Wegovy injection for now and tell the medical team exactly what you have taken, what dose you are on, and when you last injected. The NHS medicines information for semaglutide advises getting immediate help for any severe or unexpected symptoms, and vomiting blood falls squarely in that category. If you are currently mid-treatment and unsure what to do, our support team is available seven days a week and can help you decide your next step.

Why Wegovy's side effects can sometimes set the scene for this

Wegovy works by activating GLP-1 receptors, slowing how quickly the stomach empties and reducing appetite. For most people that produces manageable, temporary nausea, particularly after starting or increasing a dose. A smaller number experience frequent vomiting, which is where complications can occasionally arise, not from the medicine directly damaging blood vessels, but from the physical act of vomiting itself.

There is also a separate concern. In January 2026 the MHRA issued a Drug Safety Update flagging acute pancreatitis as a known, if infrequent, serious risk with GLP-1 medicines. The warning symptom is severe, persistent stomach pain that may radiate into the back, with or without vomiting. If that is what you are experiencing, pancreatitis needs to be excluded by clinicians urgently, it is not something to manage at home. The MHRA's Yellow Card scheme exists specifically so reactions like this are reported and tracked across the whole population using a medicine.

Pre-existing conditions also matter here. People with peptic ulcers, oesophageal varices, or gastritis who begin Wegovy treatment may find that increased vomiting aggravates something already present. This is one reason the prescribing consultation covers your full medical history (not just your weight) and why our prescribers take a complete picture before any decision is made. You can read more about how the nausea and vomiting side effect pattern typically unfolds on treatment.

What the evidence says about gastrointestinal side effects more broadly

To be clear about the trial data: in the STEP 1 trial, published in the New England Journal of Medicine, nausea and vomiting were among the most common side effects of semaglutide 2.4mg, affecting a meaningful proportion of participants, particularly early in treatment. Vomiting blood was not a listed adverse event in those trials. That distinction matters, it means the symptom you are describing is not an expected part of the Wegovy experience; it is a signal worth investigating separately.

The NHS describes the standard gastrointestinal side effects of Wegovy as nausea, vomiting, diarrhoea, constipation, indigestion, and burping, typically most pronounced in the first weeks after a dose increase and usually settling as the body adjusts. Managing these well reduces the chance of the kind of prolonged, forceful sickness that can cause secondary complications, and our page on how semaglutide causes vomiting and what you can do about it sets out what to expect in detail. Practical strategies like eating smaller portions, avoiding very fatty foods, and staying well hydrated are the usual starting points; detailed guidance on reducing vomiting on Wegovy covers these in full.

It is also worth knowing that semaglutide can, in some people, cause a temporary slowing of gastric emptying significant enough to produce bile-tinged or unusual-coloured vomit. If what you saw was yellow or greenish rather than red, our page on what it means when Wegovy causes you to vomit bile may help you make sense of what you experienced. Red or brown, however, points toward blood, and the approach is the one described above: urgent medical review.

After the emergency: what happens with your Wegovy treatment

Once you have been assessed and any acute cause is dealt with, the question of whether to restart Wegovy (and when) is one to answer with your prescriber, not alone. In some cases treatment can resume after a period of recovery. In others, an underlying condition means Wegovy is not the right option going forward. Neither outcome can be reached without a clinical conversation.

At nume, every repeat order is reviewed by a GPhC-registered Independent Prescriber before it is dispensed, a real clinician reads your notes, not an automated queue. If you have had a serious adverse event and need that conversation before continuing, reaching our team is straightforward. Treatment arrives through DPD in plain, unbranded packaging, but getting to that point safely always involves a prescriber who knows your history. For anyone considering starting Wegovy for the first time and wanting to understand the full side-effect profile before committing, our guide to vomiting as a Wegovy side effect is a useful place to read before starting that conversation through the free consultation.