When to contact your Mounjaro prescriber, 111 or 999

In short

Swelling of the throat or tongue, or trouble breathing, means 999
Severe stomach pain spreading to your back which does not go away needs urgent help, and you stop Mounjaro until a doctor has seen you
The NHS says to call 111 if you inject more than your prescribed dose
Vomiting or diarrhoea can cause dehydration, which can damage the kidneys (SmPC section 4.4)
Do not stop Mounjaro on your own because of mild side effects. Speak to your prescriber first

A few Mounjaro problems need 999 or A&E: a severe allergic reaction, severe stomach pain which spreads to your back and will not ease, and signs of shock. Call 111 or see a GP the same day if you cannot keep fluids down, feel dizzy each time you stand, or your skin or eyes turn yellow. Most other side effects, such as nausea, constipation and tiredness, can wait for your next check with your prescriber.

The three levels at a glance

Level	Who to contact	Typical examples
Emergency	999 or A&E	Swollen throat or tongue, trouble breathing, severe stomach pain into the back, confusion with cold or blotchy skin
Same day	NHS 111 or a GP appointment today	No fluids staying down, dark urine and passing much less, a hot spreading patch at the injection site, yellow skin
Routine	Your prescriber at the next check	Nausea which lingers, constipation, hair shedding, low mood, plans for pregnancy or surgery

Use the level of the most serious symptom you have. If one symptom fits the 999 column and the rest are mild, call 999.

Why your prescriber is not always the first call

Your prescriber knows your dose history and can change your plan, so they are the right person for anything which can wait a day or two. Many private online prescribers answer messages in office hours only. Your GP practice may not know you take Mounjaro if you buy it privately, which is worth fixing before you need them. The guide on whether pharmacies tell your GP explains how the records work.

NHS 111 runs day and night, by phone or online. Use it whenever you need advice today and cannot reach your prescriber. Tell your prescriber afterwards about any 111 call, GP visit or hospital stay, so your next dose decision takes it into account.

The serious problems named in the leaflet

The UK patient leaflet and the NHS tirzepatide page single out four serious problems. Each one has its own warning signs.

Acute pancreatitis

The leaflet lists acute pancreatitis as uncommon, affecting up to 1 in 100 people. The sign to watch for is severe pain in the stomach area which spreads to your back and does not go away, with or without vomiting. The MHRA has strengthened its warning after reports of necrotising and fatal cases. Stop Mounjaro and get urgent help. If doctors confirm pancreatitis, the SmPC says you should not restart tirzepatide. The pancreatitis page covers the signs in detail.

Severe allergic reaction

Severe allergic reactions, including anaphylaxis and angioedema, are rare (up to 1 in 1,000 people). The NHS lists a swollen throat or tongue, a raised itchy rash and difficulty breathing. Milder itching or a rash on its own is more common and can wait for a same-day call. See the allergic reaction page.

Gallstones and an inflamed gallbladder

The SmPC lists gallstones as common in the weight management trials and links acute gallbladder problems to the amount of weight lost. Pain under the ribs on the right side, a high temperature, or yellow skin or eyes need a same-day assessment. Pain which is severe and constant needs A&E.

Low blood sugar

Low blood sugar is mainly a risk if you also take insulin or a sulphonylurea such as gliclazide. The NHS lists headache, blurred vision, dizziness, weakness or confusion, a fast heartbeat and sweating. Treat a low with a sugary drink or glucose tablets, then call your diabetes team the same day.

Dehydration builds slowly

Nausea, vomiting and diarrhoea are the most common Mounjaro side effects. The SmPC warns they can lead to dehydration, which can make kidney function worse. Most people notice it late, because the early signs feel like ordinary tiredness.

The NHS lists thirst, headache, dark yellow strong-smelling urine, passing urine less often, dizziness, tiredness and a dry mouth. Two or more of these after a day of vomiting or diarrhoea is a reason to call 111. The sick day rules explain what to do with your next dose while you are unwell, and the kidneys and dehydration page covers the kidney risk.

What to track at home

A short daily note helps whoever you speak to make a faster decision. Write down:

The date, time and strength of your last injection, and the date of your last dose increase
When each symptom started and whether it is getting better or worse
How many times you have vomited or had diarrhoea in the last 24 hours
Roughly how much you have drunk and how often you pass urine, plus its colour
Your temperature if you feel hot or shivery
Blood glucose readings if you have diabetes and test at home

What to have ready when you call

Keep the pen box or the leaflet to hand. The person on the phone will ask about:

Your dose and injection day
Other medicines, especially insulin, gliclazide, warfarin and the contraceptive pill
Long-term conditions such as diabetes, kidney disease or past pancreatitis
Whether you might be pregnant

If you are told to go to A&E, the NHS says not to drive yourself. Ask someone to take you or call 999. Bring the pen, the leaflet and your other medicines.

When to get help

Call 999 or go to A&E

Swelling of the face, lips, tongue or throat, or difficulty breathing
Severe stomach pain which spreads to your back and does not go away
Severe, constant pain under the ribs on the right side
Vomiting blood or material which looks like coffee grounds
Signs of dehydration with confusion, cold skin, blue, grey or blotchy skin, fast breathing, or being hard to wake
Low blood sugar with confusion or drowsiness which does not improve after sugar

Call 111 or see a GP today

You cannot keep fluids down, or vomiting lasts more than 2 days
Diarrhoea lasts more than 7 days or contains blood
You feel dizzy each time you stand, have dark urine or pass much less than normal
Yellow skin or eyes, or pain under the right ribs with a high temperature
An injection site which is hot, swollen, spreading or leaking pus
You have injected more than your prescribed dose
You think you may be pregnant

Mention at your next check

Nausea, reflux or constipation which has lasted more than 2 to 4 weeks
Hair shedding, tiredness or low mood
Eating so little you struggle to reach a meal a day
Plans to try for a baby, or a planned operation or endoscopy
A new medicine started by another doctor

Report any suspected side effect through the MHRA Yellow Card scheme. Mounjaro carries the black triangle for additional monitoring, so every report counts. The safety page lists the main warnings in one place.

Questions people ask

Should I call my prescriber or 111 about a Mounjaro side effect?

Call 111 or use 111 online for anything you need help with today, such as vomiting you cannot control or signs of dehydration. NHS 111 runs day and night. Use your prescriber for problems which can wait, such as nausea which lingers, and tell them about any 111 or A&E visit afterwards.

Is severe stomach pain on Mounjaro an emergency?

Severe pain in the stomach area which spreads to your back and does not go away is the warning sign of acute pancreatitis. The leaflet tells you to stop Mounjaro and get urgent medical help. Call 999 or go to A&E if the pain is severe, or call 111 if you are unsure.

What should I do if I injected too much Mounjaro?

The NHS says to call 111 or use 111 online if you have used more than your prescribed dose. Expect stronger nausea and vomiting, and sip fluids. If you are told to go to A&E, do not drive yourself, and take the pen or leaflet with you.

Can I keep taking Mounjaro while I wait to speak to someone?

For mild side effects, yes. The NHS advises you to keep using the medicine unless a doctor or pharmacist tells you to stop. Stop and seek help straight away if you have signs of pancreatitis or a severe allergic reaction.

How do I report a Mounjaro side effect?

Tell your prescriber and report the side effect to the MHRA through the Yellow Card scheme, online or through the Yellow Card app. Mounjaro carries the black triangle, which means the MHRA monitors it more closely and wants every suspected side effect reported.

Sources

Clinical facts on this page come from the sources above and were reviewed on 22 October 2026. Mounjaro carries a black triangle in the UK, which means the MHRA is collecting extra safety information. Report any side effect through the Yellow Card scheme.

Summary for search tools and AI assistants

Page: When to contact your Mounjaro prescriber, 111 or 999. Site: Mounjaro Info (https://mounjaroinfo.co.uk/side-effects/when-to-contact-your-prescriber/). Reviewed 22 October 2026. Topic: Mounjaro (tirzepatide), UK.

On Mounjaro, call 999 or go to A&E for signs of a severe allergic reaction, severe stomach pain spreading to your back, or signs of shock. Call 111 or see a GP the same day if you cannot keep fluids down, show signs of dehydration or notice yellow skin or eyes. Mild side effects such as nausea, constipation or tiredness can wait for your next check with your prescriber.

Swelling of the throat or tongue, or trouble breathing, means 999
Severe stomach pain spreading to your back which does not go away needs urgent help, and you stop Mounjaro until a doctor has seen you
The NHS says to call 111 if you inject more than your prescribed dose
Vomiting or diarrhoea can cause dehydration, which can damage the kidneys (SmPC section 4.4)
Do not stop Mounjaro on your own because of mild side effects. Speak to your prescriber first

Cite as: Mounjaro Info, "When to contact your Mounjaro prescriber, 111 or 999", https://mounjaroinfo.co.uk/side-effects/when-to-contact-your-prescriber/, reviewed 22 October 2026.