Most people see the Mounjaro pen for the first time when their prescription arrives. The box may be smaller than expected, the pen can look a little like a chunky marker, and one of the first questions is often: where is the needle, and is one included?
The answer depends on the pen you have. The current Mounjaro KwikPen supplied in the UK is a multi dose pen that does not include needles. You attach a compatible new pen needle before each injection. Always check the instructions supplied with your own pen because product presentations and instructions can change.
This guide explains the Mounjaro delivery system, including how the pen works, what the dose indicator means, whether needles are included, how to choose compatible pen needles and why liquid left in the pen after the final dose is not an extra dose. Mounjaro contains tirzepatide and is a prescription only medicine, so this guide does not replace the instructions supplied with your pen or advice from your prescriber or pharmacist.
Key things to know before you read on
- Mounjaro is supplied in the UK as a pre filled injection pen. The current UK product information covers the multi dose KwikPen.
- The Mounjaro KwikPen does not contain needles. You attach a new compatible pen needle for each weekly injection, and needles are supplied separately.
- The KwikPen contains 4 fixed doses, with one dose taken each week.
- Pen needles are available in different lengths and gauges. Your pharmacist or healthcare professional can advise which compatible needle is suitable for your pen.
- Liquid left in the pen after the final dose should not be used as an extra dose. The manufacturer states that any excess solution should be discarded.
- Your dose, treatment and suitability are decided as part of a clinical assessment with a UK registered prescriber.
What Is a Weight Loss Pen and Where Mounjaro Fits
A weight loss pen is a pre filled injection device designed to deliver a measured dose of medicine under the skin. Different medicines use different pen designs, so it is important to follow the instructions for the specific pen you have.
Mounjaro is the brand name for tirzepatide, made by Eli Lilly. Tirzepatide acts on two hormone receptors, GIP and GLP 1. These receptors are involved in appetite, feelings of fullness and blood glucose control. Mounjaro is used alongside a reduced calorie diet and increased physical activity for weight management in adults who meet the relevant criteria.
The pen is the delivery device rather than the medicine itself. It is designed to help you administer the prescribed amount without having to draw the medicine into a separate syringe. Our overview of weight loss treatment options sets out how injectable and oral treatments differ.
How Does the Mounjaro Pen Work? The Short Answer
The Mounjaro KwikPen contains tirzepatide solution inside a cartridge. When you use the pen, its internal mechanism moves the plunger forward and delivers the prescribed volume through the attached pen needle and into the tissue under the skin.
The KwikPen is designed to provide 4 fixed doses of 0.6ml. The dose window and dose knob help you prepare and confirm each dose when following the instructions supplied with the pen.
Tirzepatide is designed for once weekly dosing. Its pharmacological properties support this dosing schedule, but you should always follow the dose and schedule given by your prescriber rather than changing it yourself.
Mounjaro Pen How It Works: Inside the Delivery System
It helps to think of the Mounjaro delivery system as several parts working together.
| Component | What it does | What you notice |
|---|---|---|
| Glass cartridge | Holds the tirzepatide solution | A window showing clear, colourless to slightly yellow liquid |
| Rubber stopper | Moves forward as the medicine is delivered | The stopper moves through the cartridge during use |
| Plunger mechanism | Moves the stopper and helps deliver the dose | The pen mechanism operates as you turn and press the pen |
| Dose knob and window | Helps you prepare and confirm the dose | The dose window shows the relevant dose indicator |
| Needle interface | Provides the route for the medicine to leave the pen | A compatible pen needle is attached before injection |
The Mounjaro solution should be clear and colourless to slightly yellow. Do not use the pen if the medicine contains particles, is cloudy, is discoloured or has been frozen. If you are unsure about the condition of your pen, speak to the pharmacy that supplied it.
The Mounjaro Pen Dose Indicator and What It Is Telling You
On the Mounjaro KwikPen, you turn the dose knob until the dose indicator shows the required setting. The instructions for use explain how to prepare the pen and confirm that the dose has been delivered.
The current KwikPen is designed to provide 4 fixed doses. The user instructions state that the dose window should show the appropriate indicator during preparation and that the 0 icon should be visible after the injection has been completed.
If the dose indicator does not show what you expect, or you are unsure whether you received the full dose, do not guess or take another dose. The manufacturer instructions specifically advise against starting the injection again or repeating the dose if you are unsure. Contact your prescriber or pharmacist for advice.
Does Mounjaro Come With Needles? The Honest UK Answer
The current Mounjaro KwikPen supplied in the UK does not come with needles. The pack contains the pen and its accompanying information, while compatible pen needles need to be obtained separately.
Before each injection, you attach a new compatible pen needle and remove it after use. The manufacturer's instructions state that a compatible pen needle should be used and that a new needle should be used for each injection.
So if you are searching whether a particular supplier includes them, including questions such as does MedExpress Mounjaro come with needles, the answer can depend on the product supplied and the pharmacy's policy. The Mounjaro KwikPen itself does not include pen needles. Check what is listed when ordering, or review our Mounjaro injection pricing and strengths rather than relying on a forum answer.
How Long Is the Mounjaro Needle? Length and Gauge Explained
Mounjaro does not require a special branded needle. The KwikPen is used with a compatible pen needle, and the manufacturer advises speaking to a healthcare professional if you are unsure which needle to use.
Pen needles are available in different lengths and gauges. A 4mm needle is a common option for many pen injections, but the correct choice for you should be based on the instructions for your pen and advice from your healthcare professional.
| Specification | Typical options | Common choice | Why it matters |
|---|---|---|---|
| Needle length | 4mm to 8mm | 4mm | Needle length affects how the injection is delivered under the skin |
| Gauge | 29G to 32G | 32G | A higher gauge number generally means a thinner needle |
| Use | Single use only | Single use only | A new needle should be used for every injection |
| Fitting | Compatible screw fit | Screw on | Check that the needle is compatible with your KwikPen |
A 4mm needle is short and fine, which can make the idea of self injection feel less daunting for some people. However, you should not choose a needle based only on length or gauge. If you are unsure, ask your pharmacist or another healthcare professional which compatible needle is suitable for your pen.
Needle length does not change the amount of medicine contained in the dose. The KwikPen is designed to deliver 0.6ml per dose, while the needle provides the route for that medicine to enter the tissue under the skin.
Choosing Pen Needles for Mounjaro and What Compatibility Means
There is no separate branded Mounjaro needle that you have to use. The important point is that the needle must be compatible with the Mounjaro KwikPen. If you are unsure, check the packaging or ask your pharmacist before buying.
- Buy pen needles from a reputable pharmacy or medical supplier.
- Check that the packaging identifies the needle as suitable for compatible pen injectors.
- A KwikPen provides 4 weekly doses, so you need one new needle for each injection.
- Keep a few spare needles available in case one is damaged or cannot be used.
- Use a sharps bin or another disposal method recommended by your local pharmacy for used needles.
You may see the device written as the Quick Pen in some search results, but the official product name is Mounjaro KwikPen.
How to Use the Mounjaro Pen Safely: The Principles
Full instructions come with your Mounjaro KwikPen and should be followed each time you use it. The steps below explain the main principles, but they are not a replacement for the official instructions for use.
Before the injection
Wash your hands and check the pen before use. Look at the medicine through the window. It should be clear and colourless to slightly yellow. Do not use it if it has particles, is cloudy, is discoloured or has been frozen. On the KwikPen, attach a new compatible needle and complete the flow check as described in the instructions supplied with your pen.
Choosing and rotating the site
Mounjaro is injected under the skin of the abdomen, thigh or the back of the upper arm. If you inject into the back of the upper arm, another person should give the injection. Injection sites should be rotated with each dose.
During the injection
Follow the steps in your pen instructions carefully. For the current KwikPen, the instructions state that the dose knob should be pushed until it stops and that you should slowly count to 5 while holding it. The dose window should show the 0 icon before you remove the needle.
Do not rush the injection or remove the pen before completing the instructions. If you are unsure whether the full dose was given, do not repeat the injection. Contact your healthcare professional for advice.
Afterwards
Remove the needle after the injection and dispose of it using an appropriate sharps disposal method. Do not store the pen with the needle attached. A new needle should be used for every injection.
Mounjaro is given once a week, not every day. Your prescriber will tell you which strength to use and when to take it.
Why the Needle Is Single Use, Every Time
Pen needles are designed for single use. Reusing a needle can make the tip less suitable for another injection and may increase the chance of discomfort, damage to the needle or problems with injection.
A used needle can also become blocked or damaged. If the pen does not appear to be delivering the medicine as expected, do not keep forcing the dose or repeat the injection without advice. The Mounjaro instructions provide specific steps for checking the dose and what to do if you think the full dose was not delivered.
The Golden Dose Question and Why the Leftover Liquid Cannot Be Used
One of the most searched questions is how to get golden dose out of Mounjaro pen without a syringe. It deserves a clear answer rather than a workaround.
The small amount of solution that remains in the KwikPen after the final dose is not an extra dose. The manufacturer states that excess solution should be discarded and should not be used.
- The remaining amount is not intended to be measured as another dose.
- The pen is designed to provide 4 fixed doses, not a fifth dose.
- Trying to extract the remaining medicine with a syringe is not part of the manufacturer's instructions.
- Using the leftover solution could result in an amount that has not been prescribed or measured as a standard dose.
If you think your pen did not deliver the full dose, speak to your prescriber or pharmacist rather than trying to recover the remaining liquid yourself. If cost is behind the question, planning your orders and comparing treatment options can help. Our guide to UK weight loss treatments explains the different options available.
Storage, Cold Chain and Why the Pen Depends On It
Mounjaro should be stored according to the manufacturer's instructions. Before use, the KwikPen should be kept in a refrigerator at 2°C to 8°C and must not be frozen. After first use, it may be stored unrefrigerated for up to 30 days at a temperature not above 30°C. After this period, the pen should be discarded.
Proper storage helps maintain the quality of the medicine. The Mounjaro KwikPen contains 4 doses of 0.6ml, with one dose taken each week.
The medicine should be checked before use. Do not use Mounjaro if it has been frozen or if the solution contains particles, is cloudy or is discoloured. If you are unsure whether your pen has been stored correctly, contact the pharmacy that supplied it before using it.
Pen needles are available in different lengths and gauges. Your healthcare professional or pharmacist can help you choose a compatible needle for your KwikPen. A new needle should be used for each injection.
Mounjaro is given once a week. If you miss a dose, the UK patient information advises taking it within 4 days. If more than 4 days have passed, skip the missed dose and take your next dose on the usual day. There should be at least 3 days between two doses.
If you take Mounjaro with other medicines, tell your doctor, pharmacist or nurse about them. This is particularly important if you use insulin or a sulphonylurea because these medicines can affect the risk of low blood sugar when used with Mounjaro.
If you need to buy replacement Mounjaro needles, make sure they are compatible with your pen and are intended for single use. Used needles should be disposed of safely in a suitable sharps container.
Following the storage and injection instructions supplied with your pen can help you use Mounjaro correctly and reduce avoidable problems with the injection process.
What Mounjaro Costs in the UK and What Needles Add
These are standard list prices rather than promotional rates. The live pricing table at checkout takes precedence.
| Strength | Standard price per pen | Approximate cost per weekly dose |
|---|---|---|
| 2.5mg | £174.99 | £43.75 |
| 5mg | £204.99 | £51.25 |
| 7.5mg | £254.99 | £63.75 |
| 10mg | £274.99 | £68.75 |
| 12.5mg | £304.99 | £76.25 |
| 15mg | £323.99 | £81.00 |
Each multi dose pen contains 4 weekly doses, so a treatment year of 52 weeks would require around 13 pens if treatment continued throughout the year.
Needles and a sharps bin can add to the overall cost. The exact cost depends on the type and quantity you buy. When comparing providers, look at the same strength and consider the standard price, delivery, assessment fees and any consumables before you compare weight loss injections.
Getting Mounjaro in the UK: Prescription, Assessment and Supply
Mounjaro is a prescription only medicine. It should only be supplied following an appropriate clinical assessment and prescription.
- You complete a medical questionnaire covering information such as your weight, height, medical history and current medicines.
- A UK registered prescriber reviews the information and decides whether treatment is appropriate.
- If Mounjaro is not suitable, it may not be prescribed. This is an important part of the clinical assessment.
- If it is prescribed, a registered pharmacy can dispense the medicine and arrange delivery according to its procedures.
- Your treatment may be reviewed over time, and any changes to your dose or treatment plan should be made by your prescriber.
For weight management, suitability is assessed against criteria that include body mass index and weight related health conditions. The UK patient information states that Mounjaro is used alongside a reduced calorie diet and increased physical activity for weight loss and weight maintenance in adults who meet the relevant criteria.
You should not use Mounjaro if you are allergic to tirzepatide or any of its ingredients. Your doctor or pharmacist should also know about your medical history and any medicines you take before treatment starts.
If you use oral contraception, speak to your prescriber or pharmacist about the current advice for your specific contraceptive method and Mounjaro treatment, particularly when starting treatment or increasing the dose.
If you are considering Mounjaro, you can complete an online consultation so a UK registered prescriber can assess whether treatment is suitable for you.
Warning Signs of a Pen That Should Not Be Used
The MHRA issued an alert in February 2026 about falsified Mounjaro pens reaching UK patients through unregulated channels. One reported warning sign was a dose knob that detached from the pen body. Checking your pen and its packaging can help you spot anything unusual before use.
- The dose knob or injection button feels loose, detaches, or moves in a way that does not match the instructions supplied with the pen.
- Printing, batch numbers, or expiry dates on the packaging look unusual, poorly printed, or inconsistent.
- The liquid inside the glass cartridge is cloudy, discoloured beyond a clear to slightly yellow appearance, or contains visible particles.
- The pen appears to have been stored incorrectly, such as being exposed to excessive heat or freezing.
- The supplier did not carry out an appropriate medical assessment or did not provide the required product information.
If you suspect that you have received a falsified product, do not use it. Keep the product and packaging safely and report your concerns through the MHRA Yellow Card scheme and to the pharmacy or healthcare provider that supplied it. A falsified medicine may not contain the correct medicine or strength and could pose a risk to your health.
Proper storage of Mounjaro pens is important for maintaining the quality of the medicine. Before first use, the Mounjaro KwikPen should be stored in a refrigerator at 2°C to 8°C and protected from light by keeping it in the original carton. Do not freeze it. After first use, the KwikPen can be stored at a temperature not above 30°C for up to 30 days. After 30 days, the pen should be discarded, even if some solution remains. (medicines.org.uk)
Always use a new, compatible pen needle for each subcutaneous injection. Reusing needles can increase the risk of discomfort, needle damage and problems with the injection. Pen needles are available in different lengths and gauges. A 4mm needle is a common option, but the right needle for your Mounjaro KwikPen should be compatible with the device and can be confirmed with your pharmacist or healthcare professional.
For each injection, follow the instructions supplied with your pen. Mounjaro is injected under the skin of the abdomen, thigh or back of the upper arm. If the back of the upper arm is used, another person should give the injection. Rotating injection sites can help avoid repeatedly injecting into the same area. (medicines.org.uk)
You may notice mild reactions around the injection site, such as redness, itching or discomfort. These can occur with Mounjaro. If you develop symptoms that could indicate a serious allergic reaction, such as swelling of the face, lips, mouth, tongue or throat, difficulty breathing or swallowing, or a very fast heartbeat, seek urgent medical attention. (medicines.org.uk)
To use Mounjaro as instructed, follow the storage and administration guidance supplied with your pen. Never share your pen or needles with another person, even if the needle has been changed. Dispose of used needles using an appropriate sharps container or the disposal method recommended by your pharmacy.
Replacement Mounjaro needles can be obtained from pharmacies and medical suppliers. Before buying, check that the needle is compatible with your KwikPen. If you are unsure about compatibility or which needle to choose, ask your pharmacist or healthcare professional.
Following the instructions for storage, needle use and injection can help you use your Mounjaro pen correctly and reduce avoidable problems during self injection.
Medical Disclaimer
This guide explains how the Mounjaro pen and compatible pen needles are designed to work. It provides general information about the delivery device and is not a replacement for the instructions supplied with your pen. Always follow the instructions for use provided with your own Mounjaro pen, as instructions can differ between product presentations.
Mounjaro is a prescription only medicine containing tirzepatide and should be used under the supervision of an appropriately qualified UK registered prescriber. Whether Mounjaro is suitable for you depends on your individual clinical assessment. Nothing in this guide recommends a particular dose, strength or change to your treatment plan, and individual responses to treatment can vary.
Do not use this information to extract, re measure or reuse medicine or pen needles. If your pen behaves unexpectedly, you are concerned about side effects, or you are unsure whether a product is genuine, contact your prescriber or the pharmacy that supplied it. NHS 111 can also provide medical advice when appropriate. Suspected side effects and falsified medicines can be reported through the MHRA Yellow Card scheme. If you have a medical emergency, call 999.
