¹Eli Lilly. How to Dispose of Mounjaro® (Tirzepatide) KwikPens® and Needles. Lilly Medical UK, 15 Aug. 2025, https://medical.lilly.com/uk/products/answers/how-to-dispose-of-mounjaro-tirzepatide-kwikpens-and-needles-217606.
Update — May 2026: The new Mounjaro pen is here
Mounjaro's manufacturer, Eli Lilly, has redesigned the KwikPen, and new pens have started arriving in UK pharmacies. The new pen looks similar to the original but has less leftover liquid after your fourth dose, removing what's been called the "golden dose." How you use the pen stays exactly the same.
If you're on a weight loss journey and have spent any time in online communities like TikTok, Reddit, or YouTube, you've likely heard of the so-called "golden dose" of Mounjaro, sometimes called "the magic fifth (5th) dose." It refers to the leftover liquid in a Mounjaro pen after the four prescribed weekly doses, and many users are asking whether they can use it as a bonus injection.
The short answer is no, and the pen itself is now changing. From April 2026, Eli Lilly began rolling out a redesigned Mounjaro KwikPen across UK pharmacies, with less leftover liquid in the pen after the fourth dose.
Below, we break down what the golden dose is, why it's there, why it isn't safe to use, and what's different about the new pen.
Key Takeaways
- The "golden dose" or "fifth (5th) dose" is the leftover liquid in your Mounjaro pen after the four prescribed doses.
- The overfill is intentional. It ensures accurate delivery of each dose, not a bonus injection.
- Eli Lilly has redesigned the Mounjaro KwikPen to reduce leftover liquid, effectively removing the golden dose. The updated pens began rolling out across UK pharmacies in April 2026.
- Always follow your prescribed dosing schedule and speak to a prescriber if your dose isn't working as expected.
What is a Mounjaro injection and how does it work?
Mounjaro (tirzepatide) is a weekly injection that works with two of your body's natural appetite-regulating hormones, GLP-1 and GIP. It reduces appetite, helps manage cravings, and improves blood sugar control, all of which support sustainable weight loss.
Each dose is delivered via a pre-filled auto-injector pen. There is no mixing, no measuring, and no manual needle handling. You inject once a week, on the same day each week, into the fatty tissue of your abdomen, thigh, or upper arm. The needle retracts automatically after use, and most people find the whole process quick and easy.
What is the Mounjaro "golden dose”?
The Mounjaro golden dose is the small amount of liquid left in your Mounjaro pen after you've used all four prescribed doses.
Every Mounjaro pen contains 3ml of liquid. Each weekly injection uses 0.6ml, which gives you four accurate, pre-measured doses. After those four doses, you'll notice there's still some liquid left in the pen.
This applies to both the original and the redesigned KwikPen. Both contain the volume of liquid needed to deliver four full doses plus the flow check before each injection. The difference is that the new pen design leaves less liquid behind after the fourth dose.
But this leftover liquid, in either pen, is not a bonus 5th dose. It's a deliberate overfill built into the pen design for two important reasons: to allow for the flow check before each injection and to guarantee each of your four prescribed doses is delivered completely.
The amount of liquid that remains can vary slightly and is not a measurable or accurate dose.
Note: These images show the original Mounjaro pen design. The redesigned pen has less leftover liquid after the fourth dose. See what's changed with the new pen →
How many doses does each Mounjaro pen contain?
Each Mounjaro pen is designed to deliver four weekly doses, giving you a four-week supply. This applies across all strengths: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. So a single Mounjaro KwikPen lasts roughly one month before it needs replacing.
After the fourth dose, some leftover liquid remains visible in the pen. This is what people refer to as the "golden dose," "fifth dose," or spare dose. The amount left over varies by pen strength and injection technique, and it is not a measured or reliable dose.
Mounjaro golden dose chart: How to track your remaining doses
Not sure how many doses you have left? This Mounjaro golden dose chart shows you exactly what your pen should look like after each injection, including what it looks like once all four doses have been used.
The chart is helpful if you're wondering whether you've injected too much or too little. You'll notice that even after four doses, liquid remains visible in the pen, but as we'll explain below, this isn't a safe or accurate dose to use.
Need a little more guidance on how to correctly take your weight loss medications? We’ve got you. See Voy’s guide to injecting Mounjaro.
What is a Mounjaro click chart and how do you use one?
Each Mounjaro KwikPen has a dose knob that you turn to load your dose. As you turn it, you hear an audible click. When "1" appears in the dose window, one full dose is loaded and ready to inject. So on a 5 mg pen, "1" means 5 mg is loaded. On a 10 mg pen, "1" means 10 mg. It takes 60 clicks to get there, regardless of pen strength.
A Mounjaro click chart maps those clicks to smaller amounts. People use them to try getting a custom dose or extra dose out of their Mounjaro pen, or to work out whether there is enough leftover liquid for an additional injection. These charts are not provided by Eli Lilly, the manufacturer of Mounjaro.
Partial dosing can be appropriate in some situations, for example when managing side effects on a particular strength, but it should only ever be done under the guidance of your clinical team. If your dose needs adjusting, your Voy clinical team can advise you safely.
What size needle does the Mounjaro pen use?
Mounjaro KwikPens are designed to work with compatible pen needles. At Voy, we supply four 4 mm, 32G needles with each pen, which are short, thin, and well tolerated. You need a fresh needle for each injection and should never reuse or share needles, including if you are partial dosing using the click chart method or attempting a golden dose. Reusing a needle increases the risk of infection, pain, and inaccurate delivery.
If you need extra Mounjaro needles, you can ask your provider or local pharmacy for ISO 11608-2 compliant pen needles.
Can you use the fifth (5th) dose of Mounjaro and is it safe?
The short answer is: No. Using the fifth dose carries serious risks, and both prescribers and Mounjaro's manufacturer strongly advise against it.
Risks of using the 5th dose
- Underdosing: The leftover liquid is not a full, measurable dose. Using it may result in underdosing, which can reduce the effectiveness of your treatment and impact your weight loss progress.
- Overdosing: Without dose control, you may inject too much, increasing the risk of Mounjaro side effects like nausea, vomiting, diarrhoea, or constipation.
- Loss of sterility: Once the Mounjaro KwikPen is used, it expires after 30 days. After this period, it must be discarded, as it might no longer be free of germs. Attempting to extract and use the remaining medication can introduce bacteria and increase the risk of infection.
Some people have tried getting the 5th dose out of their Mounjaro pen using insulin syringes or needles, while others look for ways to extract it without a syringe. Regardless of the method, these practices are unsafe and not medically supported. The Mounjaro golden dose is not a safe or approved use of the pen.
How to get the "golden dose" of Mounjaro
We understand the motivation behind this question. When you see leftover liquid in your pen, it can feel like wasted medication.
But the leftover liquid isn't meant for dosing. It exists to ensure accurate delivery of your prescribed amount and to allow for flow checks during injection. To avoid confusion and remove the risk of misuse, Eli Lilly has now redesigned the KwikPen to reduce this leftover liquid, effectively closing the door on the golden dose. Read more about the redesigned pen.
Can you extract the 5th dose from a Mounjaro pen?
On online forums like TikTok and Reddit, some users have shared how to get the golden dose out of a Mounjaro pen, including methods using insulin syringes, needles, or attempting to extract it without a syringe. These tutorials show how to get the 5th dose out of Mounjaro pens, particularly for the UK multi-dose KwikPen design.
But regardless of the method, these practices are not safe or medically supported.
Attempting to extract the extra dose from your Mounjaro pen can lead to underdosing, overdosing, contamination, and serious side effects. It's really important that you do not attempt to extract a fifth dose from your Mounjaro pen, whether using a syringe, needle, or any other method.
Instead, stick to your prescribed dosage schedule: one injection per week, using the same pen for all four weekly doses. If you're unsure about your current dose or feel it isn't working as expected, speak to a prescriber. Self-adjusting your medication without clinical guidance can be dangerous.
Can you half-dose Mounjaro or split doses between pens?
Half-dosing Mounjaro is something people ask about, particularly when side effects feel difficult to manage during a dose increase. Using the click-counting method described above, it is possible to load a partial dose from your pen, but this should only ever be done if your clinical team has specifically advised it.
Your Voy clinical team may recommend a half dose or adjusted dose in certain situations, for example if taking your full dose is causing unmanageable side effects. This is an off-label approach and is always a clinical decision, not something to try on your own.
A common question is whether taking two 2.5 mg doses across one week adds up to the same effect as a single 5 mg dose. They are not the same. Mounjaro is designed to be taken as one injection per week. A single 5 mg dose gives your body one concentration of medication to work with over the full week. Two smaller doses taken days apart mean your body is processing two separate, lower peaks instead, so the overall effect on your appetite and blood sugar is different.
If your current dose is not working for you, speak to your Voy clinical team. Dose adjustments are a normal part of treatment, and they can advise on the safest approach for your situation.
Side effects support at Voy
"If you're using Voy and you experience any side effects, rest assured that our expert clinicians are just a message or phone call away. They can adjust your dose, prescribe medication to ease your symptoms, or simply offer reassurance.
Everyone responds differently to weight loss treatment and we'll help you find what feels right for you."
What if cost is a factor?
For many people, the motivation behind the golden dose is straightforward: Mounjaro is a significant financial commitment, and leftover liquid in the pen can feel like money going to waste. That concern is completely understandable.
The problem is that attempting to use the remaining liquid does not reliably extend your supply. The amount left can vary from pen to pen, which makes it difficult to get a consistent or accurate dose. An inaccurate dose is just as likely to disrupt your treatment as it is to help it.
If cost is a concern, speak to your Voy clinical team. They can look at whether a lower dose might be appropriate, discuss switching to Wegovy which is typically more affordable, or explore other treatments like Orlistat that may better fit your budget. That is a much safer route than trying to stretch a pen beyond its intended use.
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The new Mounjaro pen: what's changed in 2026
Eli Lilly, the manufacturer of the Mounjaro KwikPen, has confirmed an updated pen design, which began rolling out across UK pharmacies in April 2026. The updated device works the same way as before. The change only affects the internal design of the pen mechanism.
The new pens are still:
- Single-patient use
- Disposable after use
- Multi-dose pens containing four weekly injections
The injection process stays the same, and you should continue using the pen exactly as before.
What does the new Mounjaro pen look like?
The new Mounjaro pen looks almost identical to the original from the outside. It's the same size, shape, and colour, with the same dose window and dial mechanism. The difference becomes clear after your fourth dose: noticeably less liquid remains in the pen than with the previous design.
What has changed inside the new pen?
The new pen works the same way as the original, but there are a few internal updates:
- When the pen is full, the plunger sits further down in the cartridge than it did before. This is because a new internal component has been added that extends the plunger.
- After your fourth dose, the plunger sits near the end of the pen, making it clearer that the pen is finished and ready to be discarded.
The result is noticeably less liquid left visible after the fourth dose. In practical terms, the updated design closes the door on the golden dose by reducing the overfill that previously made a fifth dose possible. This change reinforces the point that the leftover liquid was never intended as a usable dose.
What to do during the transition
During the rollout, pharmacies may supply both the original and updated pens for a short period while existing stock is used up. How you use the pen stays exactly the same regardless of which version you receive.
For Voy patients: the new pens have started arriving in 5mg first, with other strengths following as supplies update. If you're on 5mg, you may receive either the original or the redesigned pen depending on stock when your prescription is fulfilled. If you're on a different dose, you'll continue receiving the original design until the new version reaches your strength.
If you have any questions about which pen you've received, your Voy clinical team can help on 020 3912 9885.
The bottom line on the Mounjaro golden dose
The "golden dose" may be tempting, but safety comes first. The leftover liquid in your pen isn't a usable 5th dose, and trying to extract it can lead to inaccurate dosing, contamination, and unwanted side effects.
With updated Mounjaro KwikPens now rolling out across the UK, the golden dose is becoming a thing of the past. The new pen design reduces leftover liquid and makes it clearer when your pen has delivered all four of its prescribed doses.
At Voy, we believe in safe, clinically supported weight loss using licensed GLP-1 weight loss medications. If you have questions about your medication, dosage, or results, your clinical team can provide personalised advice to keep you on track.
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