If you have just given yourself the fourth injection from your Mounjaro pen and can still see liquid through the window, you are not imagining it. This is a common question among people using Mounjaro.
Here is the direct answer. A Mounjaro KwikPen is designed to deliver four doses. It is not designed to provide a fifth dose. Some liquid may remain in the pen after the fourth injection, but the Patient Information Leaflet says not to try to use any medicine that remains.
That answer may be disappointing, so this guide explains why liquid can remain in the pen, why you should not treat it as an extra dose, how to avoid unnecessary medicine loss, and what to do with the pen after your four doses. This page is written for UK patients and is based on UK authorised product information.
Key Takeaways
- A Mounjaro KwikPen is designed to deliver four doses of 0.6 ml.
- Some liquid may remain after the fourth dose. This does not mean that there is a fifth dose available.
- The Patient Information Leaflet advises patients not to try to use any medicine that remains in the pen.
- The amount of liquid left can vary, so it should not be used to work out another dose.
- Following the correct priming and injection instructions can help avoid unnecessary medicine loss.
- Do not try to remove, measure or inject leftover liquid from the pen.
- Your Mounjaro dose should only be changed following advice from your prescriber.
- Mounjaro is a prescription only medicine, and whether it is suitable for you is decided after an individual clinical assessment.
How Many Doses Are in a Mounjaro Pen?
Each Mounjaro KwikPen is a multiple dose, pre filled device designed to deliver four doses. These are usually given once a week according to your prescribed treatment schedule.
The Summary of Product Characteristics states that each multiple dose pre filled pen contains 4 doses of 0.6 ml solution. The Patient Information Leaflet also explains that each KwikPen contains 4 doses of Mounjaro in the available strengths of 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg and 15 mg.
The amount of tirzepatide in each 0.6 ml dose changes depending on the strength of the pen. The number of doses does not.
This means that when people search for how to get a 5th dose out of a Mounjaro pen, they are asking about liquid that may remain after the four intended doses have been given. The pen is not designed or licensed to provide this as an additional dose.
Trying to remove and use the remaining liquid is also not part of the manufacturer's instructions. Doing so can make it difficult to know exactly how much medicine you are taking and may involve handling the medicine and pen in ways that are not intended.
Understanding Accurate Dosing and the Pen Mechanism
The Mounjaro KwikPen is designed to deliver measured doses through its dose knob and dose window. Each prescribed dose is 0.6 ml and is injected under the skin of the abdomen, thigh or back of the upper arm.
The dose knob is turned according to the instructions to set the dose. The pen is designed to deliver four doses. It is not designed to measure or deliver a fifth dose from any liquid that remains afterwards.
You may see leftover liquid after the fourth injection. Some people refer to this online as the "Mounjaro golden dose". However, this is an informal term and does not describe an approved dose of Mounjaro.
Using leftover liquid could result in an uncertain amount of medicine being injected. This is why it should not be treated as an additional dose.
Risks of Using Leftover Medication or Golden Dose
Trying to use leftover liquid as a fifth dose can make it difficult to know how much Mounjaro you are taking. The amount remaining is not a measured dose, so it cannot be relied on to provide a specific amount of tirzepatide.
Taking more medicine than prescribed may increase the risk of side effects, including nausea, vomiting and other stomach or bowel problems. On the other hand, taking less than the prescribed dose may mean you do not receive the amount intended by your prescriber.
Trying to remove the remaining liquid with a syringe or needle is also outside the manufacturer's instructions. Extra handling may introduce contamination or damage the pen.
For these reasons, do not try to extract, measure or inject the leftover liquid. Follow the dosing instructions provided with your Mounjaro pen and speak to your prescriber or pharmacy if you are unsure about your dose.
Why Does Liquid Remain After the Fourth Dose?
It is possible to see some liquid remaining in the pen after the fourth dose. Seeing liquid does not necessarily mean that the pen has failed or that you have received less than your prescribed dose.
The KwikPen requires priming before injection, and some medicine can also remain within parts of the delivery system. The exact amount of liquid left can vary from pen to pen.
It is therefore not appropriate to assume that the remaining liquid is a complete fifth dose or that it contains a particular amount of tirzepatide.
The 2026 Mounjaro Pen Redesign
If you are reading about changes to the Mounjaro KwikPen in 2026, it is important to check which version of the pen and product information applies to your medicine.
The purpose of changes to the device is to support correct use and make the end of the available doses clearer. However, you should still follow the instructions supplied with your own pen.
The available strengths and prescribed dosing schedule should be followed as directed by your healthcare professional. Do not attempt to use extra liquid or remove medicine from the pen to create another dose.
Proper Storage and Disposal
Before first use, store your Mounjaro pen in a refrigerator between 2°C and 8°C. Do not freeze it.
After first use, the KwikPen may be stored at a temperature not above 30°C for up to 30 days. After this time, the pen should be discarded.
The pen should also be discarded after the four intended doses have been given. Do not try to use any medicine that remains in the pen.
Used needles should be disposed of in an appropriate sharps container according to local guidance. Never share your Mounjaro pen with another person, even if a new needle is used.
Consult Your Healthcare Provider for Dose Adjustments
If you think your Mounjaro dose needs to change, speak to your prescriber. Your dose should not be increased, reduced, delayed or extended based on the amount of liquid you can see in the pen.
Trying to use leftover liquid or changing your dosing schedule yourself can make it difficult to know how much medicine you are taking. Your prescriber can review your treatment and advise you on the appropriate dose.
| Question | Answer |
|---|---|
| Does a Mounjaro pen have 4 or 5 doses? | Four |
| How many weeks does one pen cover? | Four weeks, one weekly injection |
| How much solution is in each dose? | 0.6 ml |
| Total volume in the pen | 2.4 ml |
| Available strengths | 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg |
| Is a fifth dose licensed? | No |
| Should leftover medication be used? | No, the Patient Information Leaflet advises not to use medicine that remains |
| Where is Mounjaro injected? | Under the skin of the abdomen, thigh or back of the upper arm |
| Can leftover medication cause side effects? | Taking an uncertain or additional amount may increase the risk of side effects |
| How can I support accurate dosing? | Follow the instructions supplied with your pen and use the prescribed doses only |
Why Is There Liquid Left in Your Mounjaro Pen After Four Doses?
Seeing liquid after the final injection does not necessarily mean that your pen has malfunctioned or that you have received less than your prescribed dose.
The KwikPen is designed to deliver four measured doses. Some liquid may remain because of the way the pen and its delivery system work, including the amount used during priming and liquid that can remain within the delivery system.
It is important not to assume that the remaining liquid is a complete dose. The amount can vary, and the pen is not designed to measure or deliver it as a fifth dose.
Priming needs solution
Before an injection, the KwikPen needs to be primed according to the manufacturer's instructions. This helps prepare the pen for the injection.
Priming uses a small amount of medicine. The Patient Information Leaflet provides specific instructions for priming and injection, so follow those instructions carefully rather than repeating the process unnecessarily.
Some Liquid Can Remain in the Delivery System
Medicine can remain in parts of an injection device after the intended doses have been delivered. This can include areas within the cartridge and needle system.
The amount that remains is not necessarily the same in every pen. This is another reason why visible liquid should not be treated as a measured fifth dose.
Manufacturing and Device Tolerances
Injection devices are manufactured to deliver the labelled doses within specified requirements. There can still be some liquid remaining after the intended doses have been given.
The important point for patients is that this remaining liquid is not a bonus dose. Do not try to measure it, remove it or inject it. Once you have used the four intended doses, follow the product instructions for disposing of the pen.
What Eli Lilly Actually Says About the Leftover Liquid
There is clear guidance on this in the Mounjaro KwikPen Patient Information Leaflet, so it is better to follow the manufacturer's wording rather than rely on information shared online.
The UK Patient Information Leaflet states:
"A small amount of medicine may remain in the pen after all doses have been correctly given. Do not try to use any remaining medicine."
It also states that after the last dose, the pen must be properly discarded.
This is authorised product information for Mounjaro in the UK. If you are unsure whether you have received your full dose or what to do with your pen, speak to your prescriber or pharmacist rather than trying to use the remaining liquid yourself.
Is the 5th Dose From a Mounjaro Pen Safe?
The Mounjaro KwikPen is designed to deliver four doses. The UK Patient Information Leaflet specifically says not to use any medicine that remains after all four doses have been correctly given.
There are several practical reasons why treating the leftover liquid as a fifth dose is not recommended.
You cannot know how much you are getting
The amount of liquid remaining after the four intended doses is not presented as a measured dose. It can vary, so you cannot use the visible amount to work out how much tirzepatide you would receive.
This makes the leftover liquid unsuitable for trying to create another dose.
Taking an unplanned amount can affect your treatment
Mounjaro should be used according to the dose prescribed by your healthcare professional. Taking more or less than prescribed can change the amount of medicine you receive and may affect your treatment.
If you think your prescribed dose is no longer suitable, speak to your prescriber. Do not use leftover medicine to adjust your dose yourself.
Taking more than prescribed may increase side effects
Mounjaro can cause side effects, particularly stomach and bowel problems such as nausea, diarrhoea, vomiting, constipation and abdominal discomfort.
Taking an additional or uncertain amount could increase the risk of side effects. The UK Patient Information Leaflet also warns that taking too much Mounjaro can make you feel sick or be sick.
Do not try to access the cartridge yourself
Trying to remove leftover liquid with a syringe or another needle is not part of the manufacturer's instructions for using the KwikPen. The device is designed to deliver its four intended doses through the pen and compatible pen needles.
Handling the pen in an unintended way may introduce contamination or damage the device. If you believe there is a problem with your pen, contact your pharmacy or healthcare professional instead.
It can make it harder to work out what happened
If you use an unmeasured amount of leftover medicine and then experience a problem, it may be difficult for your healthcare professional to establish exactly how much medicine you received.
If you have a concern about your dose, a faulty pen or the amount of medicine remaining, keep the pen and contact the pharmacy that supplied it. This gives them more information to work with.
If you are considering using leftover medicine because of cost or supply concerns, speak to your prescriber or pharmacy. They may be able to discuss appropriate treatment or supply options with you.
The "Golden Dose": Where the Nickname Came From
"Golden dose" is an informal term used online by some Mounjaro users to describe liquid that remains in a KwikPen after the four intended doses.
It is important to understand that this is not a medical or dosing term. It does not appear as a recognised dose in the UK Mounjaro Patient Information Leaflet or Summary of Product Characteristics.
The current UK product information states that each KwikPen contains 4 doses and that a small amount of medicine may remain after all doses have been correctly given. It also specifically says not to use the remaining medicine.
The nickname has become popular because some people see the remaining liquid and assume it could provide an additional week of treatment. However, visible liquid does not mean that a measured fifth dose is available.
What Changed in the 2026 Mounjaro KwikPen
You may have noticed that some Mounjaro KwikPens supplied in 2026 look different from earlier versions.
The updated device changes the way the pen looks and how the plunger sits within the device. The medicine, available strengths and four dose treatment schedule remain the key points for patients to follow. The current UK product information continues to state that each KwikPen provides 4 doses of 0.6 ml.
The updated design is intended to make the end of the pen easier to recognise and can result in less visible liquid remaining than some earlier pen designs.
| Feature | Earlier KwikPen | Updated KwikPen |
|---|---|---|
| Doses per pen | 4 | 4 |
| Dose volume | 0.6 ml | 0.6 ml |
| Strengths available | 2.5 mg to 15 mg | 2.5 mg to 15 mg |
| Appearance after the final dose | Liquid may remain visible | The end of the pen may look different |
| Plunger position | Depends on the pen design | Updated design may position the plunger differently |
| Clinical treatment schedule | Four prescribed doses | Four prescribed doses |
The important point is that seeing more or less liquid does not change the number of prescribed doses in the pen.
If your pen looks different from an earlier one, check the instructions supplied with your current pen. If you believe the pen is damaged, underfilled or has not delivered a full dose, contact your dispensing pharmacy rather than trying to assess or extract the remaining liquid yourself.
How to Tell How Many Doses Are Left in Your Pen
It is better to keep track of the doses you have taken rather than trying to estimate them from the amount of liquid visible in the pen.
- Keep a simple record. Note the date of each injection so you know which weekly doses you have taken.
- Do not use the liquid level as a dose guide. The visible amount of liquid is not a reliable way to calculate another dose.
- Follow the dose window and Instructions for Use. The manufacturer's instructions explain how to prepare and use the pen correctly.
- Follow the full injection instructions. After setting and injecting the dose, follow the instructions supplied with your pen rather than relying on techniques shared online.
- Do not judge the remaining doses from the plunger alone. The appearance of the plunger can differ between pen designs.
If you think the pen has not delivered the dose correctly, do not try to make up the difference yourself. Contact your pharmacist, prescriber or the manufacturer for advice.
Overpriming: How to Avoid Unnecessary Medicine Loss
Correct priming is part of using the Mounjaro KwikPen. The manufacturer's Instructions for Use explain how to prime the pen and what to do if medicine does not appear from the needle.
It is important to follow those instructions rather than repeatedly priming the pen simply because you do not see a droplet immediately.
The current instructions allow specific additional priming steps if medicine does not appear, so it is not correct to say that every extra priming attempt is automatically harmful or that it will always cause a later dose to be lost.
If you are having difficulty priming the pen, follow the manufacturer's instructions. If the pen still does not work as described, contact your pharmacy or healthcare professional.
What that waste actually costs
Based on the standard per pen prices displayed by EveryDayMeds, the approximate cost per weekly dose can be calculated by dividing the listed pen price by 4.
| Strength | Standard price per pen | Cost per weekly dose | Value of one dose |
|---|---|---|---|
| 2.5 mg | £174.99 | £43.75 | £43.75 |
| 5 mg | £204.99 | £51.25 | £51.25 |
| 7.5 mg | £254.99 | £63.75 | £63.75 |
| 10 mg | £274.99 | £68.75 | £68.75 |
| 12.5 mg | £304.99 | £76.25 | £76.25 |
| 15 mg | £323.99 | £81.00 | £81.00 |
Standard list prices as displayed on the EveryDayMeds Mounjaro product page. Prices are subject to change and exclude any promotional offer.
Rather than trying to recover leftover liquid, the best approach is to follow the Instructions for Use carefully and use the pen as directed. If the priming process is unclear or your pen is not working as expected, ask your pharmacy before attempting anything outside the instructions.
Storing Your Mounjaro Pen Correctly
Correct storage helps protect the medicine during the time you are using it. The current UK product information gives the following storage requirements.
| Condition | Requirement |
|---|---|
| Refrigerated storage | 2°C to 8°C |
| Freezing | Do not freeze. A frozen pen must not be used. |
| Unrefrigerated storage | Up to 30°C for a maximum of 30 days after first use, then discard the pen |
| Light | Keep the pen in its original carton to protect it from light |
| After the final dose | Discard the pen properly |
If your pen has been frozen, do not use it. The Patient Information Leaflet also says not to use Mounjaro if the pen is damaged or if the medicine is cloudy, discoloured or contains particles.
After the final dose, dispose of the pen according to local requirements. Used needles should also be disposed of safely in an appropriate sharps container.
If Your Pen Genuinely Fails: What to Do
If your pen will not work as described, do not try to force it or remove the remaining medicine. The manufacturer's instructions provide specific advice for problems with the pen.
- Stop and check the Instructions for Use. Make sure you have followed the correct steps for your pen.
- Do not force the mechanism or attempt to open the pen.
- Keep the pen and packaging. The batch number and other information on the packaging may help with an investigation.
- Contact your dispensing pharmacy if you believe the pen has not delivered the prescribed dose or is faulty.
- Speak to your prescriber before changing your treatment. Do not skip, repeat, double or improvise a dose unless you have been advised to do so.
- If you suspect a medicine or device problem or experience a side effect, you can report it through the MHRA Yellow Card Scheme. Patients can report suspected side effects directly.
If you are unsure whether you received your full dose, speak to a healthcare professional before taking any additional Mounjaro.
Mounjaro Strengths, Weekly Schedule and Pricing in the UK
Tirzepatide is given as a once weekly injection. The starting dose for adults is 2.5 mg once a week for four weeks, followed by 5 mg once a week. If needed, your doctor may increase the dose in 2.5 mg steps, with at least 4 weeks at the current dose before moving to a higher dose. The maximum adult dose is 15 mg once a week.
Your prescriber will decide whether a dose increase is appropriate for you. Not everyone needs to reach the maximum dose.
| Strength | Typical treatment window | Doses per pen | Standard price per pen | Cost per week |
|---|---|---|---|---|
| 2.5 mg | Weeks 1 to 4 | 4 | £174.99 | £43.75 |
| 5 mg | Weeks 5 to 8 | 4 | £204.99 | £51.25 |
| 7.5 mg | Weeks 9 to 12 | 4 | £254.99 | £63.75 |
| 10 mg | Weeks 13 to 16 | 4 | £274.99 | £68.75 |
| 12.5 mg | Weeks 17 to 20 | 4 | £304.99 | £76.25 |
| 15 mg | Week 21 onwards | 4 | £323.99 | £81.00 |
Standard prices as displayed on the product page at the time of writing. The treatment window column reflects a typical escalation pattern only and is not a dosing recommendation. Prices can change, so check the current product page before ordering.
Questions worth asking before you buy anywhere
- Is the price shown per pen, and does the pen provide four prescribed doses?
- Is the consultation and prescriber review included, or charged separately?
- Are there delivery charges on top of the advertised price?
- Is the medicine supplied through a registered UK pharmacy?
- Are the prescribers appropriately registered and carrying out the required clinical checks?
- What happens if a pen arrives damaged or there is a problem during use?
- Is there a charge for a follow up review before your next pen?
Advertised prices are not always directly comparable. A lower product price may come with separate consultation or delivery charges, so check the total cost before ordering.
You can compare the full range of weight loss treatment options before deciding what may be suitable for you.
Who Can Be Prescribed Mounjaro in the UK
Tirzepatide is a prescription only medicine. Whether Mounjaro is suitable for you depends on your individual circumstances, medical history, current medicines and the reason for treatment.
Meeting a particular BMI or other eligibility criteria does not automatically mean that Mounjaro is suitable. A prescriber needs to assess your circumstances before deciding whether treatment is appropriate.
NHS access
NICE technology appraisal TA1026, published on 23 December 2024, recommends tirzepatide as an option for managing overweight and obesity in adults who have an initial BMI of at least 35 kg/m² and at least one weight related health condition. NICE advises that the BMI threshold is usually reduced by 2.5 kg/m² for people from South Asian, Chinese, other Asian, Middle Eastern, Black African or African Caribbean backgrounds.
NICE also recommends that after 6 months of treatment at the highest tolerated dose, the prescriber should consider whether treatment should continue if the person has lost less than 5% of their initial weight.
NHS England is introducing tirzepatide in phases. This means access can depend on where you live, the local service and your clinical circumstances. NHS availability may therefore be more limited than the wider NICE recommendation during the rollout.
Private access
Private providers have their own clinical assessment criteria. These commonly consider a BMI of 30 or above, or a BMI of 27 or above together with a weight related health condition.
A UK registered independent prescriber will review your medical history, current medicines, BMI and other relevant information before deciding whether Mounjaro is suitable for you. Meeting the provider's criteria does not automatically mean that treatment will be prescribed.
When you should speak to a clinician first
It is important to tell your prescriber about your medical history and current medicines before starting Mounjaro. In particular, speak to a healthcare professional if:
- You are pregnant, planning to become pregnant or breastfeeding
- You have a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2
- You have previously had pancreatitis or have certain digestive conditions
- You take other medicines that may affect your treatment
- You are under 18
Your prescriber can assess your individual circumstances and advise whether Mounjaro is appropriate.
For broader information about medically supervised weight management and the different treatment options, our weight management treatments hub covers the options in more detail.
What the Clinical Evidence Shows
Clinical studies can help explain how tirzepatide performed in research, but the results do not predict exactly what will happen for every person.
SURMOUNT 1 included 2,539 participants and lasted 72 weeks. In the study, average weight reductions were 16.0% with 5 mg, 21.4% with 10 mg and 22.5% with 15 mg, compared with 2.4% with placebo. Between 89% and 96% of participants receiving tirzepatide achieved at least a 5% reduction in body weight, compared with 28% of those receiving placebo.
Gastrointestinal side effects were among the most frequently reported adverse events. Nausea affected approximately 24.6% to 33.3% of participants across the tirzepatide dose groups, compared with 9.5% with placebo. Diarrhoea, constipation and vomiting were also commonly reported. Treatment was stopped because of adverse events by 4.3% to 7.1% of participants receiving tirzepatide, compared with 2.6% receiving placebo.
For UK context, the Health Survey for England 2024 found that 66% of adults aged 16 and over were overweight or living with obesity, while 30% were living with obesity.
These study results are averages from a specific research setting. Individual results can be different, and the study outcomes should not be treated as a promise of how much weight you will lose.
Ordering Mounjaro Online in the UK
If you are considering Mounjaro treatment, a regulated online pathway will usually involve several steps.
- Complete a clinical questionnaire covering your medical history, current medicines, height, weight and other relevant information.
- Independent prescriber review. A UK registered independent prescriber assesses whether treatment is clinically appropriate. Approval is not automatic, and some requests may be declined or referred for further assessment.
- Dispensing from a GPhC registered pharmacy using genuine Mounjaro supplied through the appropriate authorised supply chain.
- Temperature controlled delivery. Mounjaro has specific storage requirements, so the pharmacy should use suitable packaging and handling arrangements when sending the medicine.
- Ongoing clinical review. Your treatment and dose should be reviewed as required, particularly when your dose is being increased.
A practical tip for continuity is to start your reorder process before you need your next pen. Clinical review, prescribing and delivery can take time, so planning ahead may help you avoid an unnecessary gap in treatment.
If you are considering treatment, you can start the process through our Mounjaro injection for weight loss page.
Medical Disclaimer
This article provides general information about Mounjaro and its delivery device. It is not medical advice and does not replace advice from a qualified healthcare professional.
Mounjaro (tirzepatide) is a prescription only medicine and should be used under the supervision of an appropriately qualified prescriber. Whether treatment is suitable for you depends on your individual clinical assessment, medical history and other relevant factors.
Always follow the Instructions for Use supplied with your pen and the advice given by your prescriber or dispensing pharmacy.
Do not use medicine remaining in your pen after the four intended doses have been given. Do not change your dose, skip doses or try to modify the pen without speaking to your prescriber.
Results can vary between individuals, and this article does not guarantee any particular treatment outcome.
If you experience side effects or are concerned about your treatment, speak to your prescriber or pharmacist. You can also contact NHS 111 for advice when appropriate. Serious or severe symptoms may require urgent medical attention.
Suspected side effects can be reported through the MHRA Yellow Card Scheme.
