Can Mounjaro Cause Blood Clots? What the Evidence Actually Shows

You've read something about blood clots and Mounjaro, here's where that worry usually comes from

It's a reasonable concern, and it comes up often. Someone starts Mounjaro, loses weight, and then has a health event, a clot, a hospital admission, something frightening. The instinct is to connect the new medicine to the new problem. Sometimes that connection is real; sometimes it isn't. With tirzepatide and blood clots, the evidence currently points toward the latter.

The UK prescribing information for Mounjaro (the Summary of Product Characteristics published on the electronic Medicines Compendium) does not list venous thromboembolism (DVT, pulmonary embolism) among the known adverse effects of tirzepatide. This isn't an oversight. The SURMOUNT programme involved thousands of adults over 72 weeks, with thorough cardiovascular monitoring, and clotting events did not emerge as a signal attributed to the medicine. You can read the NHS medicines information for tirzepatide for an accessible summary of what is and isn't listed.

There is a common misconception worth letting go gently: people sometimes assume that because GLP-1 medicines affect circulation, heart rate, or blood pressure, they must also affect clotting. The pharmacology doesn't work that way. Tirzepatide acts on GIP and GLP-1 receptors involved in appetite regulation and glucose metabolism, it doesn't directly influence the coagulation cascade. The confusion is understandable, but it isn't supported by the current evidence. For a fuller picture of the range of effects tirzepatide can cause, that page covers the documented side effect profile in detail.

Why obesity itself raises clotting risk, and why that matters here

Here's the nuance that gets lost in these conversations. Obesity is an independent risk factor for venous thromboembolism. People living with a higher BMI are statistically more likely to develop a DVT or pulmonary embolism than people of lower weight, even without any medication in the picture. This is well documented in clinical literature and recognised in UK obesity management guidance from NICE's NG246 overweight and obesity management guideline.

So when someone with obesity starts a new weight-loss treatment and later experiences a clotting event, the temporal connection can feel causal. In most cases, the clotting risk was already elevated before the first pen was used. Losing weight through treatment like Mounjaro may, over time, reduce some of those baseline cardiovascular risks, though any such benefit for an individual patient depends on many factors and would be assessed by their prescriber rather than assumed.

This is exactly the kind of context that a structured clinical assessment covers. Prescribers at our clinical team review each patient's full health picture (including any history of clots, relevant medications, and comorbidities) before approving treatment. It isn't a box-ticking exercise.

What is actually listed in Mounjaro's safety profile

The documented side effects of Mounjaro are predominantly gastrointestinal: nausea, vomiting, diarrhoea, constipation, indigestion, and reflux are the most frequently reported. These tend to be most noticeable at the start of treatment or after a dose step, and they often ease within a couple of weeks as the body adjusts.

There are also rarer but more serious effects that do warrant attention. In January 2026, the MHRA issued a Drug Safety Update for GLP-1 receptor agonists highlighting acute pancreatitis as an infrequent but potentially serious risk: severe, persistent stomach pain that spreads to the back (with or without vomiting) needs urgent medical review. Gallbladder problems, allergic reactions, and dehydration from persistent vomiting or diarrhoea are also flagged in the prescribing information. None of these are blood clots, but they are real considerations. You can report any suspected side effects through the MHRA's Yellow Card scheme.

If you're curious about a specific symptom or concern beyond clotting (skin reactions, for instance, or neurological questions) the spots and skin page and MS-related query page address those separately with the same evidence-first approach.

What to do if you have a clotting history or current anticoagulant treatment

A personal or family history of DVT or pulmonary embolism, or a current prescription for anticoagulants like warfarin or a DOAC, is exactly the kind of information that belongs in your consultation. It doesn't automatically exclude you from treatment, but it changes the clinical conversation significantly.

GLP-1 medicines can slow gastric emptying, which affects how quickly oral medications are absorbed. For patients on warfarin specifically, changes in body weight and diet during treatment can alter INR stability. These are prescriber-level discussions, not something to navigate from a product page. The dedicated page on Mounjaro and blood clots goes into more clinical detail if you want to read further before a consultation.

Anyone considering Mounjaro who donates blood regularly may also want to check the guidance on giving blood while taking tirzepatide, it's a practical question that comes up more than you'd expect. If you'd like to understand the cost side of treatment alongside the clinical picture, our Mounjaro pricing page sets out what's included transparently. When you're ready to take the next step, check your eligibility with our prescribers, the consultation is free, and a real clinician reviews your answers the same day.