How to Use Mounjaro KwikPen UK: Step-by-Step Injection Guide
Mounjaro KwikPen is a once-weekly injectable medicine used for weight management where clinically appropriate. Correct injection technique helps ensure you receive your prescribed dose safely and confidently.
This UK guide explains how to prepare your Mounjaro KwikPen, where to inject, how to use a new needle, how to dispose of sharps, what to do if you miss a dose, and when to seek medical advice.
This guide supports, but does not replace, the patient information leaflet or advice from your prescriber, pharmacist or nurse.
Last reviewed: June 2026
Next review due: September 2026
Once weekly
Mounjaro is injected once a week, on the same day each week where possible.
Doses per pen
The UK Mounjaro KwikPen contains 4 fixed doses, one dose taken weekly.
Injection areas
You can inject into the abdomen, thigh, or upper arm.
Days after first use
After first use, the pen can be kept below 30°C for up to 30 days.
Before you use Mounjaro KwikPen
Before injecting, read the patient information leaflet and the instructions for use supplied with your pen. Follow the instructions from your prescriber, pharmacist or nurse.
Mounjaro is a prescription-only medicine. It should only be used by the person it was prescribed for. Do not share your pen with anyone else, even if the needle has been changed.
Do not use Mounjaro if: the medicine name or strength does not match your prescription, the pen is expired, damaged, frozen, cloudy, discoloured, or contains particles. Contact your pharmacy or clinical team for advice.
If you are considering treatment but have not started yet, you can read more on our Mounjaro treatment information page or start a clinical assessment.
What you need before injecting Mounjaro
Prepare everything before you start. This makes the injection easier and reduces the chance of mistakes.
Mounjaro KwikPen
Check the label, dose strength, expiry date and appearance of the solution.
New pen needle
Use a new compatible needle for every injection. Never reuse needles.
Alcohol wipe or swab
Use this to clean the red inner seal and, where advised, the injection site.
Sharps container
Used needles should go into a sharps bin or suitable sharps disposal container.
Gauze or cotton wool
Useful if there is a small drop of blood or liquid after injection.
Your dose schedule
Know your weekly injection day and the dose prescribed for you.
Where do you inject Mounjaro?
Mounjaro is injected under the skin, called a subcutaneous injection. Do not inject into a vein or muscle.
| Injection site | How to use it | Practical tip |
|---|---|---|
| Abdomen | Inject into the stomach area, avoiding the area close to the belly button. | Often easy for self-injection. Avoid scars, bruises, moles or irritated skin. |
| Thigh | Use the front of the thigh. | A good option if you prefer not to inject into your abdomen. |
| Upper arm | Use the back of the upper arm. | This is usually easier if someone else gives the injection. |
Rotate your injection site. You can use the same general area, such as the abdomen, but choose a different spot each week to reduce soreness, irritation or skin changes.
How to inject Mounjaro KwikPen: step-by-step
The exact pen instructions must come from the leaflet supplied with your medicine. The steps below are a patient-friendly summary for the UK Mounjaro KwikPen.
Wash your hands
Wash your hands with soap and water. Choose a clean, well-lit area where you can sit or stand comfortably.
Check the pen
Pull the pen cap straight off. Check that the medicine name and strength match your prescription. Check the expiry date and make sure the liquid is clear and colourless to slightly yellow.
Do not use the pen if it looks damaged, frozen, cloudy, discoloured or contains particles.
Clean the red inner seal
Wipe the red inner seal with a swab before attaching the needle.
Attach a new needle
Use a new compatible pen needle for each injection. Pull off the paper tab, push the capped needle straight onto the pen and twist until it is tight.
Remove the outer needle shield and keep it. Remove the inner needle shield and place it in the household bin.
Prime the pen as instructed
Follow the leaflet instructions for priming. This step helps check that medicine flows from the needle. If you are unsure how to prime your pen, contact your pharmacist or clinical team before injecting.
Select your dose
Turn the dose knob as shown in the instructions for use until the correct dose indicator is displayed. Do not use the small cartridge marks as dose indicators.
Choose and clean the injection site
Select your abdomen, thigh or upper arm. Avoid skin that is sore, bruised, red, hard, scarred or irritated. Clean the area if advised, then allow it to dry.
Insert the needle
Insert the needle into the skin as shown in the leaflet. Keep the pen steady during the injection.
Inject the dose
Press the dose knob in until it stops. Keep holding the dose knob in and count slowly as instructed in the leaflet to make sure the full dose is delivered.
Remove the needle from your skin
Pull the needle straight out. If you see a small drop of blood or liquid, gently press the area with gauze or cotton wool. Do not rub the injection site.
Remove and dispose of the needle
Carefully replace the outer needle shield, unscrew the needle and place it into a sharps container. Do not store the pen with a needle attached.
Put the pen cap back on
Replace the pen cap and store the pen safely for your next weekly dose, unless it was your fourth dose and the pen is now finished.
Not confident? Do not guess. If you are unsure about any step, ask your pharmacist, prescriber or nurse before injecting. You can also contact the Live Well Weight Loss team if your treatment was supplied through us.
After your Mounjaro injection
After injecting, take a moment to check the injection site and safely dispose of the needle.
- A tiny drop of blood or liquid can be normal.
- Do not rub or massage the area after injecting.
- Never reuse the same needle.
- Never leave a needle attached to the pen between doses.
- Record your dose and injection day if this helps you stay on track.
- Dispose of the pen after 4 weekly doses.
Sharps bin advice
Used needles should go into a sharps bin or suitable sharps disposal container. Do not put loose needles into household rubbish or recycling.
When your sharps bin is full, follow your local council or pharmacy advice for disposal. Do not try to empty a sharps bin yourself.
How to store Mounjaro KwikPen
Correct storage helps protect the medicine.
| Storage situation | What to do |
|---|---|
| Before first use | Store in a refrigerator between 2°C and 8°C. Do not freeze. |
| After first use | The pen can be stored unrefrigerated below 30°C for up to 30 days, then it must be discarded. |
| If frozen | Do not use the pen if it has been frozen. |
| Between injections | Remove the needle, replace the pen cap and keep the pen out of sight and reach of children. |
| After 4 doses | Dispose of the pen safely, following local advice. |
Do not use the pen if it is expired, damaged, cloudy, discoloured, contains particles, or has been frozen.
What if you miss a Mounjaro dose?
If you miss a dose, follow the patient leaflet or advice from your prescriber.
| How late are you? | What to do |
|---|---|
| 4 days or less since the missed dose | Use Mounjaro as soon as you remember. Then continue with your next dose on your usual scheduled day. |
| More than 4 days since the missed dose | Skip the missed dose. Take your next dose on your usual scheduled day. |
| Thinking of doubling up? | Do not use a double dose to make up for a missed dose. |
| Changing injection day | There should be at least 3 days between doses. |
If you have missed several doses or had a longer treatment gap, speak to your prescriber before restarting. You may need dose review to reduce the risk of side effects.
Side effects and warning signs after injecting Mounjaro
Some people experience side effects, especially when starting treatment or increasing dose. Common side effects can include nausea, vomiting, diarrhoea, constipation, indigestion, reduced appetite and injection site reactions.
Tips that may help mild side effects
- Eat smaller meals.
- Avoid greasy, fried or very rich foods.
- Drink fluids regularly.
- Try bland foods if you feel nauseous.
- Do not increase dose without prescriber approval.
For more practical lifestyle support, read our Mounjaro lifestyle advice guide.
Seek urgent medical advice if you develop:
- Severe or persistent abdominal pain, especially if it spreads to your back
- Repeated vomiting or inability to keep fluids down
- Signs of dehydration, such as dizziness, confusion or passing very little urine
- Swelling of the face, lips, tongue or throat
- Difficulty breathing or swallowing
- Fainting or severe dizziness
- Sudden changes in vision
- Symptoms of low blood sugar if you also use insulin or sulfonylureas
You can report suspected side effects through the MHRA Yellow Card Scheme.
Common Mounjaro injection mistakes to avoid
Reusing needles
Always use a new needle for each injection. Reusing needles can increase pain, infection risk and blocked needle problems.
Storing with the needle attached
Remove the needle after each injection. Do not keep the pen stored with a needle attached.
Injecting into the same exact spot
Rotate injection sites to reduce irritation and skin changes.
Using the wrong dose
Check the dose strength on the label and follow your prescribed schedule.
Using a damaged or frozen pen
Do not use if the pen has been frozen, damaged, cloudy or discoloured.
Doubling up missed doses
Do not double your dose to make up for a missed injection.
Mounjaro injection FAQs
How often do I inject Mounjaro?
Mounjaro is injected once weekly. Try to inject on the same day each week. If you need to change your injection day, make sure there are at least 3 days between doses.
Where is the best place to inject Mounjaro?
Mounjaro can be injected into the abdomen, thigh or upper arm. Many people find the abdomen or thigh easiest for self-injection. Rotate sites each week.
Does the Mounjaro injection hurt?
Most people find the injection manageable. You may feel a small pinch or sting. Letting the pen reach room temperature before injecting may reduce discomfort, but always keep within the storage instructions.
Do I need to use a new needle every time?
Yes. Use a new compatible needle for every injection. Never reuse needles.
How many doses are in a Mounjaro KwikPen?
The UK Mounjaro KwikPen contains 4 fixed doses. One dose is injected weekly. After 4 doses, the pen should be disposed of.
Can I share my Mounjaro pen?
No. Do not share your Mounjaro KwikPen with anyone else, even if the needle has been changed.
What should I do if I miss a dose?
If it has been 4 days or less since the missed dose, use it as soon as you remember. If it has been more than 4 days, skip the missed dose and continue on your usual day. Do not use a double dose.
Can I inject Mounjaro cold from the fridge?
Follow the leaflet instructions. Some people find injections more comfortable if the pen is not very cold, but do not use heat to warm it and do not leave it outside the permitted storage conditions.
What should I do if the liquid looks cloudy?
Do not use the pen if the liquid is cloudy, discoloured or contains particles. Contact your pharmacy or clinical team.
When should I seek medical help after Mounjaro?
Seek urgent advice for severe abdominal pain, repeated vomiting, dehydration, allergic symptoms, breathing difficulty, fainting, or sudden vision changes.
References
- electronic Medicines Compendium. Mounjaro KwikPen Instructions for Use. Available at: medicines.org.uk
- electronic Medicines Compendium. Mounjaro Patient Information Leaflet. Available at: medicines.org.uk
- MHRA. Mounjaro tirzepatide authorised for weight management and weight loss. Available at: gov.uk
- MHRA Yellow Card Scheme. Report suspected side effects. Available at: yellowcard.mhra.gov.uk
This article is for general information only and does not replace the patient information leaflet or advice from a healthcare professional. Mounjaro is a prescription-only medicine. Suitability, dosing, injection technique, side effects, missed doses and treatment continuation should be reviewed with an appropriate healthcare professional.
