The company
Penwise is made and published by Version Two s.r.o., a software company registered in Slovakia. We are not a clinic, a pharmacy, a telehealth service or a compounding operation, and we do not sell, prescribe or supply medication. We sell one app, and the only money that changes hands is a subscription or a one-off purchase through the App Store or Google Play.
That matters more than it sounds. A tracker owned by a company that also sells you the drug has an interest in what you log. We do not. There is no advertising business behind Penwise, no data partner, and no third party paying for access to anything you write down.
Why the app has no server
Every design decision in Penwise starts from one constraint: a medication history is one of the most sensitive things a person can write down, and the safest place for it is the phone in their pocket. So there is no account, no sign-in, no sync service, and no Penwise server holding health data. We could not hand your log over, sell it or lose it, because we never receive it.
The honest version of that promise includes its cost. Because there is no server, there is no password reset and no way for us to recover anything. A backup is encrypted on your device with a passphrase only you hold; lose the passphrase and the backup is gone. We would rather say that plainly than quietly keep a copy so support is easier.
Where the numbers in our guides come from
The guides on this site repeat a lot of specific figures: half-lives, click counts, in-use windows, dose ladders. Each of those has a source, and we treat them differently depending on how solid that source is.
Since 2026 each guide also lists its own references at the foot of the page, linking to the product information a regulator publishes or to the trial it draws on, so a figure can be checked against its source rather than taken on trust.
Label and regulator documents
Dose ladders, in-use storage windows, injection intervals and the number of doses in a pen come from the manufacturer leaflet and the clinical-pharmacology sections of the regulator reviews. These are the figures we state flatly, because they are printed on the box.
Published pharmacokinetics
Elimination half-lives – about seven days for semaglutide, about five for tirzepatide, about thirteen hours for liraglutide – come from published clinical pharmacology. Penwise uses them in a one-compartment model with first-order absorption to estimate a level curve.
Device arithmetic
Click counts follow from the pen mechanism: a detent advances a fixed volume, so the milligrams a click delivers depend on the concentration of the pen in your hand. We show the arithmetic rather than a number to memorise, because two pens labelled the same are not the same.
Community practice
Some of what people actually do – counting clicks, using leftover volume – is off-label and manufacturers advise against it. Where we describe it, we label it as community practice, say what the manufacturer says, and never present it as guidance.
When a figure varies by market, product generation or the version of a pen you were dispensed, we say so instead of picking the tidiest number. The redesigned tirzepatide KwikPen is the clearest example: the same brand, the same box, and a materially different device behaviour.
What an estimated level is, and is not
The medication-level curve is the flagship feature of the app and the thing most likely to be misread, so it gets its own paragraph here as well as in the app. It is a model. It takes the doses you logged, applies published absorption and elimination rates for that medication, and draws where the curve would be for an average person on that schedule.
It is not a measurement of anything in your blood. Real people differ in absorption, body composition and clearance. Penwise never presents the curve as a lab value, never labels it with a clinical unit, and never suggests a dose based on it. What it is genuinely good for is shape and timing: seeing that you are on the downslope, or that a level has not yet had time to plateau after a dose increase.
The line we do not cross
Penwise is a tracking and education tool. It is not a medical device, and every part of the product is built to stay on the right side of that line.
- No insight is a clinical finding, and no insight recommends changing a dose.
- Nothing in the app or on this site is a substitute for your prescriber.
- We make no claim about how much weight anyone will lose.
- The dose-splitting calculators are off by default, behind an explicit warning, and deliberately absent from our marketing.
- Insights appear only when there is enough of your own history behind them, so the app stays quiet rather than inventing a pattern.
Corrections
If a figure on this site is wrong, we want to fix it rather than defend it. Write to us with the page and the source and we will correct it, and move the update date on the page so it is visible that it changed.
Trademarks
Ozempic, Wegovy, Rybelsus, Saxenda and Victoza are trademarks of Novo Nordisk A/S. Mounjaro, Zepbound and Trulicity are trademarks of Eli Lilly and Company. We name them because those are the pens people hold and the words people search for. Penwise is not affiliated with, endorsed by, sponsored by or connected to either company, and nothing on this site should be read as their statement.
Getting in touch
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