How to Get 5mg Out of a 10mg Mounjaro Pen: The Safe Answer (October 2026)

01 · Your options

What to do if you need 5mg and hold a 10mg pen

The safe answer is to use the pen only at the dose it is made for, and to ask a prescriber for the strength you actually need. It is not a 5mg pen with extra in it, and nothing about its design supports halving a dose.

Three situations lead most people to this question, and each has a licensed answer:

• 10mg feels too strong. Stepping down means a 5mg pen, not a divided 10mg one.
• You want to save money. It is tempting to stretch one pen across two doses, but that is unlicensed and has no safety data.
• You are switching provider. If you are moving to us on 10mg, we can supply that strength; a new customer's first order at any dose is £40 less with code FIRST40, and a prescriber reviews you first.

You can see the current Mounjaro pen prices for every strength. All six doses (2.5mg to 15mg) are in stock, so there is no need to improvise with the wrong pen.

02 · Cost

What the right pen costs compared with a 'split' pen

A 5mg pen currently costs £218.99 and a 10mg pen £290.99 at standard price, per month (one 4-week pen). Those are the live prices as of October 2026, and a new customer's first order is £40 less, with every later order £25 less than the standard price.

If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £959.96 at standard price. A first year costs £2,711.88 if you stay on 5mg after your 2.5mg starting pen, up to £3,599.88 if you step up through every dose to 15mg, again before discounts.

03 · Ordering

How getting the right strength works

Getting the right pen takes three steps, and the consultation is free with no obligation.

• Free online consultation. A short health questionnaire; start through our free weight loss consultation.
• Prescriber review. A GPhC-registered prescriber reviews your answers. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.
• Dispatch and delivery. Our registered pharmacy dispenses it, with same-day dispatch when ordered by 3pm and free next-day tracked delivery in temperature-controlled packaging.

Needles, a sharps bin and injection guidance come with every order, so there is no reason to reuse equipment or find workarounds. Our team is available Monday to Friday, 9am to 5pm, on 0333 207 0413 or support@everydaymeds.co.uk if you are unsure which strength your prescription covers.

Related guides: How to get 2.5mg out of a 10mg mounjaro pen and How to get 5mg out of 15mg mounjaro pen and How to get 2.5mg out of a 5mg mounjaro pen.

04 · Why the pen can't be split

Why a 10mg pen can't give you 5mg doses

A 10mg Mounjaro pen cannot be turned into two 5mg doses because it is a pre-filled, multi-dose pen made to deliver a fixed number of whole doses at its labelled strength. Mounjaro is supplied as a KwikPen in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg, and each pen contains four weekly doses.¹ The strength on the label is the strength each of those four injections is meant to deliver.

That is why advice to 'count a certain number of clicks to get 5mg' is unreliable: the pen is not calibrated for you to measure fractions that way, and the window is the only confirmation the pen provides.

There is also a practical safety logic. Any attempt to alter doses outside the licence means unknown dosing accuracy and no safety data.¹ Tirzepatide has a half-life of about five days, so a dose that is too high takes a long time to clear, roughly 4 to 5 weeks after a final dose, and nothing can speed that up.¹ Getting a dose wrong is therefore not something you can quickly undo.

If you came here looking for a loophole, there is a more useful route: tell your prescriber what is not working at your current dose. They can do something a pen cannot, which is change the plan itself. Our related guide on splitting a 10mg pen covers the same question from another angle.

05 · Stepping down within the licence

The licensed way to move from 10mg to 5mg

If you want to be on 5mg instead of 10mg, the licensed way is a prescriber-led change of dose and a 5mg pen. The dose ladder is built around this flexibility. Everyone starts on 2.5mg once a week; after at least 4 weeks the dose increases to 5mg, and can then step up by 2.5mg at minimum 4-week intervals (7.5mg, 10mg, 12.5mg) up to a maximum of 15mg weekly, depending on how you respond and tolerate it.¹¹¹

Higher is not automatically better. Many people settle at a maintenance dose of 5mg, 10mg or 15mg, and your prescriber guides the right pace.¹ That means 5mg is a recognised maintenance dose in its own right, not a lesser fallback.

So the conversation to have is not 'how do I get half a dose', it is 'I am struggling on 10mg, what are my options?' Useful details to bring include:

• Which day of the week the symptoms hit hardest and how long they last.
• How long you have been on 10mg and what dose came before.
• Any new medicines, illness or change in eating habits.
• Whether your appetite is now so low that eating enough is difficult.

With us, ongoing monthly reviews, dose-titration and follow-up assessments are handled by the prescribing team, with side-effect support, and repeat orders re-check suitability. There is no auto-shipping, so you will not be sent a pen at a strength you have moved away from.

If you already hold a 10mg pen you no longer want, speak to the pharmacy or your prescriber rather than attempting to use part of it. The 5mg pen costs £218.99 at standard price, and your Mounjaro pen order can be changed to the strength you are prescribed. Our hub on the Mounjaro starting-dose price also explains how the first pens are priced.

06 · Pen storage and 30-day life

Storage and how long a pen lasts

A Mounjaro pen in use can be kept out of the fridge not above 30°C for up to 30 days, after which it should be discarded.¹ Four weekly doses take 28 days, so a pen used on schedule finishes within that 30-day window.

Storage basics from the product information:

• Keep pens in a fridge at 2 to 8°C and never freeze them.
• Keep the pen cap on to protect it from light.
• Never use a pen that has been frozen.
• Once in use, not above 30°C for up to 30 days, then discard.

Unopened pens should be kept in the fridge and keep until the expiry date printed on the box. If an unopened pen has been out of the fridge, check with the pharmacy before using it rather than relying on a remembered day limit, because figures circulating online often come from other countries' labels.¹

Travelling? You can fly with Mounjaro. Carry pens in hand luggage, because hold luggage can fall below freezing, ideally in a cool bag with the prescription label or a copy of your prescription. In-use pens tolerate up to 30 days not above 30°C, so most holidays need no special arrangements; for hot climates use an insulated pouch. Check destination rules for travelling with prescription injectables before you fly.

If your pen was left somewhere warm or may have frozen, do not take a chance. Phone the pharmacy; we can advise on whether to replace it. Our support team is available Monday to Friday, 9am to 5pm.

07 · Results on 5mg versus 10mg

What results to expect on 5mg and 10mg

Both 5mg and 10mg are effective maintenance doses, and the trial figures show benefit at each. In the SURMOUNT-1 trial of 2,539 adults, people taking tirzepatide alongside diet and exercise lost on average 15% of their body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.² These are trial averages and individual results vary.

As a worked example only: for someone starting at 100 kg, 15% is about 15 kg and 19.5% is about 19.5 kg. Trial averages do not predict your own result, and treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.

At 72 weeks, 85% of participants on 5mg, 89% on 10mg and 91% on 15mg had lost at least 5% of their body weight. Half of participants on 10mg and 57% on 15mg lost at least 20% of their body weight.² So the great majority on 5mg still lost at least 5%, which is relevant if you are weighing up whether stepping down would cost you the benefit.

Pace is another reason not to chase a precise dose. Weight loss on Mounjaro is gradual by design. The first weeks on 2.5mg are an adjustment phase and losses are usually modest; most measurable progress builds from 5mg onward, month by month. Trials measured results at 72 weeks, so think in months, not days, and judge progress by trend, not individual weigh-ins.¹

Review points also exist. If you have lost less than 5% of your starting weight after 6 months on the highest dose you can tolerate, your prescriber will discuss whether continuing or stopping is right for you. If 10mg is not tolerated, the highest tolerated dose may well be 5mg or 7.5mg, and that is a legitimate plan.

Early weeks differ widely. Some people notice appetite change and early loss in week one, others feel little until a higher dose, and both are normal. Early loss includes water weight, so the trend over weeks matters more than any single weigh-in. Mild nausea, altered appetite and tiredness in the first days after each injection are the commonest early effects and usually settle.

08 · Injection routine and missed doses

Injection day, time and missed doses

Mounjaro is injected under the skin once a week, on the same day each week, at any time of day, with or without food.¹ There is no 'best' time of day: it works the same morning or evening. What matters is the same day each week, so pick a day and time you will remember. Many people choose a weekend morning so early side effects fall on days off.

Licensed injection sites are the stomach area (at least 5cm from the belly button), the front of the thigh, or the back of the upper arm if someone else gives the injection. Rotate the site with each dose. Follow the pen's instructions for the injection itself.

Missed doses have a clear rule. If you miss a dose, take it as soon as you can within 4 days (96 hours) of the scheduled time, then carry on with your usual day. If more than 4 days have passed, skip the missed dose entirely and take the next one on your normal day. Never take two doses within 3 days of each other.¹

You can also change your injection day if needed, as long as at least 3 days (72 hours) have passed since your last dose.¹

A simple routine that avoids mistakes:

• Take the pen out of the fridge per the leaflet and check the label shows your prescribed strength.
• Attach a new needle and set the dose by turning the knob until your dose shows in the window.
• Confirm the number, not any clicking sound.
• Inject in a rotated site and dispose of the needle in the sharps bin.
• Note the date in a tracker. The free GLPTrackr companion app, for iOS and Android, can log doses and sites.

If at any point the number in the window is not the dose on your prescription, stop and ask. Being 'close enough' is not a safe standard with a medicine that clears slowly.

09 · Serious side effects

Serious side effects: when to get help straight away

Serious side effects are uncommon but need urgent attention. Seek immediate medical help for: severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing. If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion) — your prescriber may need to adjust those medicines.¹

10 · Eligibility, NHS and private care

Who it is for, and NHS versus private access

Mounjaro is licensed for weight management in adults with a BMI of 30 or above, or a BMI between 27 and 30 with at least one weight-related condition such as high blood pressure, high cholesterol, obstructive sleep apnoea, cardiovascular disease, prediabetes or type 2 diabetes.¹ It must be used alongside a reduced-calorie diet and increased physical activity. A prescriber assesses your BMI, medical history and current medicines before deciding whether it is suitable for you.

On the NHS, Mounjaro is available, but access is being phased in over several years. NICE recommends it for adults with a BMI of at least 35 plus at least one weight-related condition, and the NHS primary-care rollout began in June 2025 with the highest-need groups first, initially BMI 40+ with four or more qualifying conditions.⁴⁶ Full rollout is expected to take years, which is why many people who meet the licensed criteria choose regulated private treatment rather than waiting.

Whichever route you use, the dose you are prescribed is the dose the pen should deliver. If you are on NHS-supplied pens and your dose needs to change, your NHS prescriber arranges the new strength. If you are private, the prescribing team at your pharmacy does.

Supply matters too. Our Mounjaro comes through official LillyDirect supply, direct from Eli Lilly's UK distribution, as genuine KwikPens. That is relevant to anyone tempted by unofficial sellers offering pens, vials or 'pre-split' doses: offering to supply without a consultation or prescription is a warning sign, and counterfeit medicine alerts are published by the MHRA.⁷ A prescription-only medicine should only be supplied after a consultation reviewed by a GPhC-registered prescriber. You can check our registration (GPhC 9012878) on the GPhC register.

If you want to see everything we offer beyond Mounjaro, our page of weight loss treatments sets them out, and payment can be by Visa, Mastercard, Klarna or pay-monthly options, with no subscriptions.

Mounjaro (tirzepatide) is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber. Individual results vary. This page is information, not a substitute for medical advice.