Each Mounjaro KwikPen contains 4 weekly doses, with every injection delivering the same 0.6ml volume of solution regardless of the pen's strength. That holds across all six strengths, from 2.5mg to 15mg — so one pen covers four weeks of once-weekly treatment at its labelled dose.
What changes between strengths is the concentration of tirzepatide, not the volume you inject: a 2.5mg pen and a 15mg pen both deliver 0.6ml per dose (2.4ml across the four doses); the higher-strength pens are simply more concentrated. In clicks, every full dose is 60 clicks — see the clicks chart for every dose × pen combination.
Whichever strength you use, the pen must be discarded after the four doses are used or 30 days after first use, whichever comes first.
The dosing schedule and titration
Mounjaro follows a structured titration plan so your body adjusts gradually. Per the official prescribing information, treatment starts at 2.5mg once weekly for four weeks, then increases to 5mg; further increases can be made in 2.5mg increments after a minimum of four weeks at the current dose, up to a maximum of 15mg.
The recommended maintenance doses are 5mg, 10mg and 15mg weekly — 2.5mg, 7.5mg and 12.5mg are stepping-stone doses used during titration. Your prescriber decides when and whether to increase, based on how well you tolerate the current dose. The titration planner maps the full schedule in clicks and weeks.
- Start at 2.5mg weekly for the first 4 weeks
- Increase to 5mg weekly after that initial period
- Further increases in 2.5mg increments, after at least 4 weeks at each step
- Never combine two lower-strength doses to substitute for a higher one
- All dose changes should be agreed with your prescriber
Is there a fifth dose?
The "fifth dose" (or "golden dose") question comes up constantly. The official position is clear: the pen is designed to deliver four doses, and any residual solution exists to ensure those four doses are delivered accurately — it is not a bonus dose. The dial mechanism won't let you select a full fifth dose, and using leftover solution with a syringe is off-label, with real accuracy and sterility risks.
Original pens did contain a meaningful overfill, which is where the community folklore comes from — but from April 2026 Lilly rolled out a redesigned KwikPen whose plunger reaches the tip of the cartridge, removing most of that leftover. For the full story, see how long does a Mounjaro pen last?
Storage and handling
Before each injection, check the pen label to confirm you have the right strength — an easy mistake when you're holding two strengths mid-titration — and check the solution is clear and colourless.
- Keep unused pens refrigerated (2–8°C) and protected from light
- After first use: store below 30°C and discard after 30 days, even if doses remain
- Never freeze the pen; keep it away from direct heat and sunlight
- Attach a new needle for each injection and never reuse or share needles
- Rotate injection sites — see where and how to inject
- Dispose of used pens and needles in a sharps bin, not household waste
Missed a dose?
The official rule: take a missed dose as soon as possible within 4 days (96 hours) of when it was due. If more than 4 days have passed, skip it and take your next dose on the regular day. Never take two doses close together to catch up. If you want to permanently shift your injection day, keep at least 3 days between doses — the full detail is in what to do if you miss a dose.
Work out your own pen
If you dial partial doses by click-counting, the maths changes — a 2.5mg dose from a 10mg pen is 15 clicks, so one pen stretches to more, smaller doses. The clicks calculator converts any dose to clicks for your pen strength, and the pen tracker keeps a running total of what's left after mixed doses.