Mounjaro Golden dose

Mounjaro ‘Golden dose’ or ‘Fifth dose’ is used to refer to the liquid that is left in the Mounjaro pen once you have finished your 4 fixed doses prescribed by your doctor. Not using the remaining liquid may feel wasteful, but it’s in fact more wasteful for your long-term treatment effectiveness if you do try to use it.

In this guide, you can find more out about the ‘Golden dose’ idea that has been circling the weight loss social communities, why people are trying to use it, and why it’s less ‘golden’ than it seems. We’re here to break down the risks of using the ‘Fifth dose’, and discuss manufacturer recommendations, so that you can feel informed and confident in using your pen properly.

The small amount of liquid left in the Mounjaro pen after the 4 doses have been injected are being referred to on social media as the ‘5th dose’ or ‘Golden dose’.

The manufacturer increased the price of Mounjaro in September 2025, making it an expensive treatment, so it might appear wasteful to leave the leftover liquid and dispose of it. However, this amount is not enough to make up for a safe full dose to take.

Each pen contains 4 doses of 0.6ml liquid. The remaining liquid is to make sure that these full doses are complete and that patients have the right amount of liquid to prime their pens before dosing. The remaining liquid is not a full 0.6ml dose and is not tested for patients to take.

Yes, it is unsafe and you also risk reducing the effectiveness of your treatment too. The ‘5th dose’ is an inaccurate dose of your treatment and can cause an inconsistency in your doses. Mounjaro pens are designed so that you can administer the clinically correct fixed amount of medication as prescribed by your doctor. There is no such thing as a ‘5th dose’ in a 4 dose pen.

If you use medication incorrectly by injecting the ‘5th dose’ this could lead to:

Underdosing or overdosing

Underdosing or overdosing can happen when you do not take the correct and prescribed amount of medication that is safe. In this case, if you used up the remaining fluid in your injection. This can limit how effective your treatment is.

Tirzepatide (Mounjaro) requires once-weekly dosing, which is delivered through 1 dose of your Kwikpen, to achieve its full benefits and help you lose weight. Clinical studies have shown that the effectiveness of tirzepatide is directly dependent on accurate, measured doses – this is why your dosage is slowly increased when you begin Mounjaro.

The dosage schedule does not include the unmeasured leftover fluid after the 4th dose.

Side effects

Medications like Mounjaro that contain a glucagon-like peptide-1 (GLP-1) receptor agonist are most effective when they are taken steadily and with predictable, prescribed doses. If you take your doses inconsistently, this includes taking a ‘5th dose’, it can potentially worsen or cause other Mounjaro side effects, commonly gastrointestinal ones like feeling or being sick (nausea and vomiting).

Contamination

The Mounjaro pen is intended for you to use 4 measured doses. The residual fluid in your pen is for safety and to allow you to prime your pen. Once you have used your pen 4 times, the leftover fluid has been in the cartridge for 4 weeks (28 days) and is only safe up until day 30 of opening it. This increases contamination risk from the time you have previously injected your pen as it has come into contact with the air, as well as the liquid potentially being past its expiration date of opening.

Taking a 5th dose of Mounjaro comes with a risk of side effects because you will be taking a clinically unknown and untested dosage amount, as a result, managing side effects becomes harder.

Glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 are natural hormones that Mounjaro mimics when injected. They work with your blood sugar (to produce more insulin), your appetite (to signal fullness to help you lose weight) and your digestion (to slow it down, helping your appetite and blood sugar stay under control). These medications are safe to use in the way that they have been clinically tested to be used to be effective.

Not following the Mounjaro dosage schedule, taking too much, or too little of a GIP/GLP-1 receptor agonist like tirzepatide can be dangerous, and can lead to side effects like:

In some cases, these can be severe and increase your risk of dehydration. If you’ve taken too much Mounjaro, speak to your doctor straight away.

The manufacturer of Mounjaro, Eli Lilly, advises against using the KwikPen after the 4th dose of Mounjaro has been taken. Eli Lilly states that the KwikPen is designed in a way that only allows patients to inject 4 fixed and measured doses. Leftover fluid (the ‘Golden dose’) cannot be dialled so is not recommended or safe to inject. Instead, it must be discarded.

Remaining fluid in your Mounjaro pen is for priming, which is a process that allows you to check if your pen is safe to use the first time you use it. Priming removes air from your injection cartridge, which makes sure your pen is working properly before you inject. Priming is an important part of the process of injecting your medication.

If you are unsure how to prime your pen, follow these steps:

1. Wash your hands with soap and water.
2. Pull the pen cap off, check – the pen label to ensure you have the right dose and it has not expired, it is not broken or damaged, the medication is not frozen, cloudy, or has particles, or the liquid is colourless or slightly yellow.
3. Wipe the red inner seal with a swab.
4. Select a new pen needle, always use a new pen needle for each injection to prevent infections or blocked needles. Pull off the paper tab from the outer needle shield.
5. Push the capped pen needle onto the pen and twist the needle on tightly.
6. Pull off the outer needle shield and keep it (this will be reused), and pull off the inner needle shield, you can put this in your household bin.
7. Slowly turn the dose knob until you hear 2 clicks and an extended line is shown in the dose window. This is the prime position.
8. Hold your pen with the needle pointing up, tap the cartridge holder so that it collects the air bubbles at the top.
9. Release medication into the air by pushing the dose knob in until it stops, count to 5 as you hold the dose knob. The ‘0’ icon must be showing in the dose window. Do not inject this into your body.
10. You should see a small amount of medication come out of the tip of the pen needle. This means your pen has been primed.

If you do not see medicine, repeat steps 7 to 9 no more than 2 times. If you still do not see medication, repeat steps 7 to 9 with a new needle, and only repeat up to 1 more time. If you do not see medication after this stage, you should contact your doctor or medication supplier.

Once you have safely injected your 4 doses of Mounjaro, you must dispose of your:

• needles in a sharps container (not in household waste)
• KwikPen in household bin or sharps disposal container after removing the needle

We understand why patients taking Mounjaro may want to explore whether they can get a 5th dose out of their pen. Weight loss treatment is expensive, and seeing remaining liquid may feel wasteful.

However, this remaining liquid is not intended by the manufacturer to be an extra dose, it’s designed to have extra fluid to make sure you can inject your 4 doses safely by allowing you to do flow checks and priming.

In online forums or on social media, some people say they are trying to inject the ‘5th dose’ by withdrawing leftover fluid with a syringe. This is dangerous and it is not medically supported. It can expose the medication to non-sterile surfaces, or contaminated air. Even small amounts of bacteria can cause infection. By trying to extract a 5th dose you risk contamination.

Instead, you should follow the Mounjaro dosage schedule, and only inject doses that are safe and measured to take. Any dose taken outside of these are not prescribed or measured.

No. It may feel wasteful to not use the remaining liquid in your Mounjaro pen, otherwise known as the ‘Golden’ or ‘5th dose’. However, we do not recommend injecting any fluid left in your pen after your 4 fixed doses have been injected as it is not safe to do so, and this dose would be unmeasured.

By injecting the remaining liquid in your Mounjaro pen you risk:

• reducing long-term effectiveness – tirzepatide is effective at measured doses and unmeasured doses may disrupt treatment
• overdosing or underdosing – leading to side effects or ineffective treatment long term
• increased side effects – such as nausea, vomiting, and diarrhoea
• contamination and infection – risk of repeated air exposure or using the liquid after its expiration date (after 30 days of opening)

You must only inject the 4 fixed doses of Mounjaro prescribed by your doctor and follow the Mounjaro dosing schedule. We recommend keeping any remaining or excess fluid to check and prime your pen to ensure it is safe to use before injecting.

• Dose-Dependent Efficacy and Safety of Tirzepatide for Weight Loss in Non-diabetic Adults With Obesity: A Systematic Review and Meta-analysis of Randomized Controlled Trials, Cureus [accessed 20 October 2025]
• How many doses of Mounjaro are there in the KwikPen?, Eli Lilly [accessed 20 October 2025]
• Mounjaro KwikPen, Eli Lilly [accessed 20 October 2025]
• Mounjaro KwikPen 2.5mg solution for injection in pre-filled pen, emc [accessed 20 October 2025]
• Tirzepatide, BNF [accessed 20 October 2025]