Mounjaro overdose: signs, symptoms and what to do

Ready to take the next step? See if you're eligible for expert-led weight loss support.

Have you taken too much Mounjaro? Get clear, expert advice on what to do next and what symptoms to watch for.

Have you taken more Mounjaro than you were supposed to?

Let's make sure you get the support you need. In this guide, we show you:

What to do if you take too much Mounjaro
Signs and symptoms to watch for
When to seek medical support

What to do if you accidentally take a double dose of Mounjaro

Don't panic. While taking a double dose is never recommended, symptoms can usually be managed at home with supportive care.

Follow these steps:

STOP injecting: don't take any more medication for now.
MONITOR your symptoms: watch for side effects that you don't recognise, feel worse than usual or get worse over time.
CALL NHS 111 or your Semapen team if you're concerned or need advice.
CALL 999 straight away if you:

Feel faint
Have signs of low blood sugar (shaking, sweatiness, dizziness, rapid heartbeat)
Have signs of an allergic reaction (difficulty breathing; swollen lips, tongue or throat)
Have severe stomach pain that radiates to your lower back

Signs and symptoms of a Mounjaro overdose

Unlike some other medications, Mounjaro won't cause poisoning if you take too much. However, that doesn't mean it's OK to double dose at home.

That's because overdosing on Mounjaro can make side effects much worse. The more you take, the worse these side effects are likely to be.

Watch for:

Nausea: this is common. Nausea appears in around 90% of patients who visit A&E after overdosing on a weight loss injection.
Vomiting is also common.
Other gastrointestinal symptoms, including diarrhoea and abdominal pain.
Signs of low blood sugar (hypoglycaemia): this is less common than the other symptoms, but can happen.

These symptoms are similar to what you might already experience on Mounjaro. The key thing is to listen to your body and watch for anything that feels unusual or keeps getting worse. Bear in mind that these side effects might take some time to appear.

In rare cases, Mounjaro overdoses can cause severe symptoms like acute hypoglycaemia, ketoacidosis (acidic blood) and dangerous mineral deficiencies.² These symptoms can be life-threatening and require hospital treatment.

When to seek medical assistance

Monitor symptoms…	Seek advice…	It's an emergency…
If you experience side effects that are worse than usual but feel manageable (nausea, vomiting, etc.)	If you feel very dizzy or confused, can't keep fluids down or keep vomiting for a long time.	If you have severe, radiating abdominal pain, signs of low blood sugar or signs of an allergic reaction.
WHAT TO DO: rest, stay hydrated and monitor your symptoms.	WHAT TO DO: call NHS 111 or your Semapen clinical team for advice.	WHAT TO DO: call 999 straight away.

What counts as a Mounjaro overdose?

Mounjaro users follow an escalating dosage schedule. It typically looks like this:

2.5mg for the first 4 weeks
5mg for weeks 5 to 8
7.5mg for weeks 9 to 12
10mg for weeks 13 to 16
12.5mg for weeks 17 to 20
15mg for week 20 and onwards

Your schedule might look a little different, depending on how you've tolerated the medication so far.

In any case, taking an overdose means you've taken more than you've been prescribed at your current stage of treatment.

This might happen because:

You forget you've already taken a dose and inject the medication again.
You're not sure if the first dose worked so inject again.
You were sent the wrong dose (this is rare, but it can happen).
You didn't receive clear instructions with the medication. This is common with compounded (unlicensed) Mounjaro, where patients often receive a vial and a syringe rather than a pre-measured pen.

How is a Mounjaro overdose treated?

There is no antidote to a Mounjaro overdose. Instead, treatment involves managing symptoms and providing supportive care.

In mild cases, symptoms can often be managed at home. This means:

Getting plenty of rest
Drinking plenty of fluids (vomiting can make you dehydrated)
Seeking support from NHS 111 or your Semapen clinical team where needed

Severe overdoses may require hospital treatment. This often includes intravenous (IV) fluids, anti-nausea medication and careful observation of symptoms and vital signs.

Bear in mind that Mounjaro has a half-life of five days.¹ In simple terms, that means symptoms may take a while to appear and may need monitoring for some time. However, most mild cases resolve within eight to 24 hours with supportive care.

Why are Mounjaro overdoses on the rise?

Poison centres in the US saw a 1,500% increase in calls related to weight loss drugs between 2019 and 2025.³

One obvious reason is that more people are using the medications. In the US, usage increased by 700% in the four years to 2023.⁴ Meanwhile, an estimated 1.6 million UK adults have used weight loss drugs in the past year.⁵

However, it's unlikely this is the only reason for the increase in overdoses.

Medical experts note cases where patients have taken much more than described – often because of unclear instructions from off-brand compounding pharmacies.⁶

As endocrinologist Dr Ajay Rao told Medscape, "When patients get clear directions from their prescribing providers and [obtain] non-compounded versions of these medications, I feel less concerned about it being a problem."⁶

However, when patients receive unregulated versions of drugs or unclear instructions, "I get very worried about it", Rao said.⁶

This underscores the need for effective clinical support for weight loss medications – something that's central to our approach here at Semapen.

Weight loss medications like Mounjaro are safe, but only when taken as part of a clinician-led programme including careful monitoring and expert guidance. As compounded and unregulated versions of weight loss injections become more prevalent,⁷ the risk of improper support – and therefore overdoses – will only rise.

Semapen is a UK provider of clinically supported weight loss programmes. Learn more about our unique, expert-led weight loss app today.

Sources

1. Eli Lilly and Company (2025) How do you treat a Mounjaro® (tirzepatide) overdose? Retrieved from https://medical.lilly.com/us/products/answers/how-do-you-treat-a-mounjaro-tirzepatide-overdose-165458

2. Sharafeldin, M. et al. (2025) "Severe Adverse Effects of Tirzepatide Overdose Requiring Intensive Care Unit Admission and Complex Rehabilitation" Cureus, 17(12) https://doi.org/10.7759/cureus.98681

3. America's Poison Centers (n.d.) Glucagon-like Peptide-1 (GLP-1) Agonists. Retrieved from https://poisoncenters.org/track/GLP-1

4. Mahase, E. (2024) GLP-1 agonists: US sees 700% increase over four years in number of patients without diabetes starting treatment [news story]. BMJ. Retrieved from https://www.bmj.com/content/386/bmj.q1645

5. Jackson, S.E. (2026) "Prevalence of use and interest in using glucagon-like peptide-1 receptor agonists for weight loss: a population study in Great Britain" BMC Medicine, 24:1 https://doi.org/10.1186/s12916-025-04528-7

6. Larkin, M. (2026) GLP-1 Overdoses on the Rise: Cause for Concern? [feature]. Medscape. Retrieved from https://www.medscape.com/viewarticle/glp-1-overdoses-rise-cause-concern-2026a1000dob

7. Rehman, A. & Nashwan, A.J. (2024) "The rising threat of counterfeit GLP-1 receptor agonists: Implications for public health" Journal of Medicine, Surgery, and Public Health, 3:100136 https://doi.org/10.1016/j.glmedi.2024.100136

This article was reviewed and approved by Lujain Alhassan, Bariatric Nutritionist, on 23 July 2026.

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