Six strengths, and why the ladder is slower than it looks
Tirzepatide steps in 2.5 mg increments: 2.5, 5, 7.5, 10, 12.5 and 15 mg, weekly. The usual pattern is four weeks at 2.5 mg as a starting dose, then four weeks at each step you climb. Nobody is required to reach 15 mg, and plenty of people settle at 5, 7.5 or 10 mg because it is doing the job.
Four weeks per step is not a formality. Tirzepatide has an elimination half-life of about five days, so a new dose takes roughly four weeks to settle into a stable weekly rhythm. Climb faster than that and each increase lands on a level that is still rising, which is where a lot of unnecessary nausea comes from.
| Step | Weekly dose | Typical duration |
|---|---|---|
| Starting dose | 2.5 mg | 4 weeks, not a treatment dose |
| First treatment dose | 5 mg | 4 weeks or longer |
| Step up | 7.5 mg | 4 weeks or longer |
| Step up | 10 mg | 4 weeks or longer |
| Step up | 12.5 mg | 4 weeks or longer |
| Maximum | 15 mg | Maintenance, if you get there |
The label schedule. Your prescriber decides the pace, and holding a step for months is normal. Dose schedules and titration covers every product.
KwikPen or single-use, and why it changes your supply maths
Zepbound comes as a four-dose KwikPen and as a single-use pen, and they are not interchangeable when it comes to counting what you have left.
| KwikPen | Single-use pen | |
|---|---|---|
| Doses in the device | 4 | 1 |
| Volume per dose | 0.6 ml | 0.5 ml |
| Days usable once started | 30 | n/a |
| Clicks for a full dose | 60 | no dial |
The KwikPen also changed. The original design finishes with liquid still in it, which is the origin of the “extra dose at the end” conversation. Lilly began shipping a redesigned device in April 2026 that finishes essentially empty, so that leftover is not there any more. Both generations are in circulation and the packaging looks the same, so Penwise asks which one you have rather than guessing on your behalf.
The thirty-day clock, counted for you
A started KwikPen may be used for 30 days, whatever is left in it. Four weekly doses is 28 days, which sounds like plenty of room until the week you shift a shot, hold a dose or run a pen at a reduced strength. Then the discard date arrives before the pen is empty.
Penwise tracks both clocks: how many doses are left at your current strength, how many days that is, and whether that plan outlasts the window the pen is allowed to be used for. It says so before it happens rather than after. More in how long a GLP-1 pen lasts.
Weight, read against the dose
Zepbound is prescribed for weight, so the weight trend is the headline number – and on its own it is close to useless. A trend line only means something laid against the dose you were on, the weeks you were unwell, and the weeks you were late.
Penwise keeps weight, body fat, lean mass, waist and resting heart rate on the same timeline as the dose log, with a goal weight and progress against it. A scale that talks to Apple Health or Health Connect feeds it automatically. When the loss slows, the question “did anything change four weeks ago” has a real answer, which is most of what makes a plateau readable rather than frightening.
Where you are in the cycle
A tirzepatide dose peaks about a day after injection and falls with a five-day half-life. Weekly dosing means the curve never returns to zero, but the trough is real and a lot of people feel it: the appetite comes back, the food noise returns, the last two days before a shot feel different from the first two after it.
Penwise+ models that curve from your logged doses using published pharmacokinetics. It explains the week you are having rather than predicting the next one. The arithmetic is in how long tirzepatide stays in your system, and it is an estimate, not a blood test.
Sites, pain and the rotation nobody remembers
Abdomen, thigh, upper arm, rotating over months. Penwise puts the sites on a body map, suggests the least recently used one, and stores the pain score you recorded for each. After two months you have an actual answer about which site is least unpleasant for you, which is usually not the one you would have guessed. See GLP-1 injection sites.
Private by construction
There is no Penwise account, no sign-in and no server that receives health data. A weight-management history with a drug name attached is exactly the kind of record people are careful about, and the safest architecture is the one where we never receive it. Export is free and unlimited; an exported backup is encrypted on your device with a passphrase we do not hold.
Track Zepbound properly, from 2.5 to 15
Free core tracker, no account, nothing sent anywhere. Fourteen days of Penwise+ included, no card needed.
Common questions
Is Zepbound the same as Mounjaro?
Is there a free Zepbound tracker app?
How long does a Zepbound KwikPen last once started?
Do I have to reach 15 mg?
Can Penwise track compounded tirzepatide?
Is Penwise connected to Eli Lilly?
Sources
Every factual claim on this page traces to the product information a regulator publishes, or to a published trial. Links open on the site of whoever issued the document.
- Zepbound (tirzepatide) prescribing information DailyMed, U.S. National Library of Medicine
- Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1) New England Journal of Medicine, 2022
- Continued Treatment With Tirzepatide for Maintenance of Weight Reduction (SURMOUNT-4) JAMA, 2024
Penwise is a tracking and education tool, not a medical device. Nothing on this page is medical advice, a diagnosis or a recommendation to start, stop or change a dose. Dosing decisions belong to you and your clinician. Ozempic, Wegovy, Rybelsus, Saxenda and Victoza are trademarks of Novo Nordisk; Mounjaro, Zepbound and Trulicity are trademarks of Eli Lilly. Penwise is not affiliated with, endorsed by or connected to either company.