Mounjaro Dose Between the 2.5mg Pen and 5mg (October 2026)

01 · The decision

What to do instead of an in-between dose

Stay on 2.5mg for longer, or move to 5mg when your prescriber agrees. Those are the two licensed routes. Everyone starts on 2.5mg once a week, and the dose can increase to 5mg after at least 4 weeks.¹ The 2.5mg starting dose is about letting your body adjust, not about weight loss itself.¹¹

Our guide to moving from 2.5mg to 5mg covers what the first weeks at the higher dose can feel like.

02 · Cost

What the two pens cost

A Mounjaro pen at 2.5mg costs £169.99 per month and 5mg costs £218.99. Your first 2.5mg pen costs £129.99 with code FIRST40. Every later order is £25 off the standard price, and all six doses are in stock. If you step up after 4 weeks on each dose, your first four pens (2.5mg to 10mg) cost £959.96 at standard prices; a new customer's first order is £40 less and every later order £25 less.

Our free consultation is reviewed by a GPhC-registered prescriber, so you can start your consultation and ask about pacing your dose. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full.

03 · How the pen works

How the KwikPen dial works

You set the dose by turning the knob until the correct dose shows in the window. Our page on Mounjaro clicks explains this in more detail.

A 2.5mg pen is designed to deliver 2.5mg doses and nothing else. You can read about the pen itself in our KwikPen guide.

04 · Why not microdose

Why you should not make your own dose

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

The licensed ladder already starts low for tolerability. Your prescriber can adjust the pace within it, which is the safe way to get a gentler step.

05 · Why doses increase

Why Mounjaro doses step up

Doses increase gradually so your body can adjust, and the dose can then step up by 2.5mg at a minimum of 4-week intervals, to a maximum of 15mg weekly.¹ Many people settle at 5mg, 10mg or 15mg. Higher is not automatically better, and your prescriber guides the pace.¹¹

In the SURMOUNT-1 trial of 2,539 adults, average weight loss at 72 weeks was 15% on 5mg, 19.5% on 10mg and 20.9% on 15mg, against 3.1% with lifestyle changes alone. These are trial averages, and individual results vary.²

06 · Injecting and timing

Injecting, missed doses and storage

Mounjaro is injected under the skin once a week, on the same day each week, at any time of day, with or without food. Licensed 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 injects. Rotate the site each dose.¹ Our guide on injecting the 2.5mg pen goes step by step.

If you miss a dose, take it as soon as you can within 4 days (96 hours) of the scheduled time. After that, skip it and take the next one on your normal day, and never take two doses within 3 days of each other.¹

Keep pens in the fridge at 2–8°C and never freeze them. An in-use pen can stay out of the fridge not above 30°C for up to 30 days, then it should be discarded.¹³

07 · Getting a prescription

Getting a prescription and the next dose

Mounjaro is prescription-only, supplied after an online consultation reviewed by a GPhC-registered prescriber. We supply genuine KwikPens through official LillyDirect supply, with free next-day tracked delivery in temperature-controlled packaging and same-day dispatch when ordered by 3pm. See our online prescription guide and our page on lowest prices. For the starting pen, see Mounjaro 2.5mg and our 2.5mg injection price page.

Across the UK pharmacies we track, starting pens range from £143.96 to £179.99 (checked 10 October 2026). Browse all weight loss treatments if you are comparing options.