A Mounjaro KwikPen is designed to deliver four full weekly doses. Dialling each dose to the stop uses 60 clicks, so a pen holds 240 usable clicks in total. If you take the pen's full labelled dose once a week, that's four weeks per pen.
Why some pens last longer than four weeks
Many people don't use the pen's full labelled dose. For example, while easing into treatment you might dial 2.5mg from a 5mg pen — that's only 30 clicks, so the same pen gives eight 2.5mg doses instead of four 5mg ones, lasting eight weeks at a weekly cadence.
Spacing injections further apart also stretches a pen. Dosing every ten days instead of weekly means each pen covers more calendar time, though the number of doses stays the same.
The 'golden dose'
Original KwikPens were slightly overfilled. Beyond the four labelled doses there was roughly 0.6ml left — about 60 extra clicks — that some people drew out with a syringe as a fifth dose. This is off-label, isn't endorsed by the manufacturer, and carries sterility and accuracy risks, so only consider it with professional guidance.
Important: from April 2026 Eli Lilly began rolling out a redesigned KwikPen whose plunger reaches the tip of the cartridge, removing most of this overfill — so the 'golden dose' is largely unavailable on newer pens. The medicine, its strength and the four labelled doses are unchanged; only the leftover is reduced.
Work out your own pen
To see exactly how long your pen will last at your dose and frequency, use the calculator — it shows doses per pen and weeks per pen. If you've already taken a few different-sized doses, the pen tracker tells you how much is left.