How Much Is Left in a 5mg Mounjaro Pen? (October 2026)

01 · The short answer

How much is left in a 5mg Mounjaro pen?

The amount left in a 5mg pen is simply four doses minus the injections you have already taken. Each KwikPen contains four weekly doses, so after one injection three remain, after two injections two remain, and so on.¹

The pen is built so you do not need to measure anything. You turn the dose knob until the number in the window shows your dose. If the pen holds enough medicine for a full dose, it dials. If it does not, it stops.¹³

The simplest way to track it is to write the date of each injection on the box or in a notes app. Our companion app GLPTrackr is free for iOS and Android and logs each injection for you.

If you are reading this because you can see liquid in the pen after your fourth dose, our guides on why there is so much left in the pen and Mounjaro left over in the pen go through it in more detail.

02 · Cost and ordering

What a 5mg pen costs and how to order the next one

A 5mg pen is four weeks of treatment and costs £189.99 at the standard price, which works out at £47.50 per week. You can see all six strengths and current availability on the Mounjaro pen product page, where all doses are in stock.

New customers save £40 on their first order at any dose with code FIRST40, including people moving to us from another provider on 5mg. An automatic £25 reorder discount applies to every future order (code DOSE25).

If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £879.96 at standard prices. A first year costs £2,399.88 if you stay on 5mg after your 2.5mg starting pen, up to £3,279.88 if you step up through every dose to 15mg. A new customer's first order is £40 less and every later order £25 less.

Ordering works in three steps. First, complete the free online consultation, which has no charge and no obligation, and is reviewed by a GPhC-registered prescriber. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full. Then our registered pharmacy dispenses it, with same-day dispatch when you order by 3pm and free next-day tracked delivery in temperature-controlled packaging. You can start your free consultation whenever you are ready.

03 · Dose window, not clicks

How many clicks does the Mounjaro pen make?

The number of clicks does not tell you your dose, and you should not count them. You set the Mounjaro KwikPen by turning the dose knob until the dose indicator shows the correct dose in the window.

This is why questions such as "how many clicks is 2.5 on a 5mg pen?" have no safe answer. Each pen is a fixed-dose device for its strength: a 5mg pen delivers 5mg doses, and the window is the only check you should rely on.

Before each injection, follow the preparation steps in the patient information leaflet, which is in every box.¹³ Our guide to preparing your Mounjaro pen walks through them in plain language.

04 · Does the pen lock?

Does the Mounjaro pen lock after four doses?

Each pen contains four weekly doses.¹

Do not try to top up from a second pen or combine the remains of two pens to make one dose. That is not a use the pen is designed for.

If the pen feels stuck before your fourth dose, that is a different problem. See how to unjam a Mounjaro pen, and contact the pharmacy or your prescriber rather than forcing the knob.

05 · Splitting or stretching doses

Can I take 2.5mg from a 5mg pen, or half of a 5mg dose?

No. That covers taking 2.5mg out of a 5mg pen, taking half of a 5mg dose, and splitting a 15mg pen into 5mg doses.

The reason is accuracy. Altering doses outside the licence means unknown dosing accuracy and no safety data.

Tell the prescribing team how you feel; that is what the monthly reviews are for.

06 · Using leftover Mounjaro

Can I use leftover Mounjaro?

The licensed course is one dose a week, with four doses in each pen, and the pen will not dial a full dose once those are used.¹

Our related guides cover the same question from different angles: what happens at the end of a Mounjaro pen and medicine left in a Mounjaro pen.

A part-used pen between doses is normal, because each pen covers four weeks. Keep it with the cap on to protect it from light. Once in use, a pen can be kept out of the fridge at a temperature not above 30°C for up to 30 days after first use, and must then be thrown away. Do not use a pen that has been above 30°C or frozen.¹

Never share a pen with anyone else, even if it still holds doses. Pens are dispensed for one named person; see why sharing a Mounjaro pen is unsafe.

07 · Twice-weekly and missed doses

Can I take 2.5mg twice a week?

No. Mounjaro is licensed as a once-weekly injection, taken on the same day each week.¹

The licensed rules for timing are clear. 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 and take the next one on your normal day. Never take two doses within 3 days of each other.¹

You can change your injection day if at least 3 days (72 hours) have passed since your last dose. A missed dose does not add a dose to the pen: it still holds four. Once the pen is in use, keep it not above 30°C and throw it away after 30 days.

08 · Why 5mg is not the finish line

Where 5mg fits in the dose ladder

5mg is the first step up from the starting dose, and for many people it is where they stay. Everyone starts on 2.5mg once a week. After at least 4 weeks the dose rises to 5mg, and it can then step up by 2.5mg at minimum 4-week intervals to a maximum of 15mg. Many people settle at a maintenance dose of 5mg, 10mg or 15mg; higher is not automatically better, and your prescriber will guide the right pace.¹¹

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 over 72 weeks, compared with 3.1% with lifestyle changes alone. At 72 weeks, 85% of participants on 5mg had lost at least 5% of their body weight. These are trial averages, and individual results vary.² For someone starting at 100 kg, 15% is about 15 kg.

Treatment is used alongside a reduced-calorie diet and increased physical activity. Your prescriber reviews your response: if you have lost less than 5% of your starting weight after 6 months on the highest dose you can tolerate, they will discuss whether continuing or stopping is right for you.¹¹

If you are weighing up your next step, see the Mounjaro starting-dose price guide or browse all weight loss treatments. For a table covering every strength, read how much is left in a Mounjaro pen at all doses.