Semaglutide Tracker App
A semaglutide tracker keeps a once-weekly injection routine honest: the day and time of each injection, the site, whether it came from a prefilled pen or a compounded vial, the lot and expiry dates of that supply, and the weight trend alongside it. Pepti does that on your iPhone with no account. It records the figure you already have; it never tells you what dose to take.
By Tessaro Pty Ltd, the maker of Pepti · Reviewed
This page covers the app side of tracking semaglutide: what to set up once, what to log each week, and how pen and vial records differ. For the compound itself — trials, half-life, and why we publish no dosing — see the semaglutide reference page; its sources are listed below. It is written by the maker of Pepti, so read the Pepti-specific parts as a description of our own app.
Get Pepti on the App StoreWhy a weekly injection is easy to lose track of
Semaglutide is given as a once-weekly subcutaneous injection, per its US label; a once-daily oral tablet is also approved, including for chronic weight management in the US since December 2025 (US FDA, NDA 218316). This page is about the weekly injection. One entry a week sounds easy to remember, and that is the problem: with seven days between injections there is nothing daily to anchor it. Was it Sunday evening or Monday morning? Left side or right? A daily habit corrects itself through repetition; a weekly one relies on a week-old memory.
A tracker swaps that memory for a record. A semaglutide log is short by nature — one entry a week — so completeness matters more than volume: a single missing week leaves a visible hole, and a vague entry blurs the weeks around it.
Setting up semaglutide in Pepti
Setup happens once. Add semaglutide, set the schedule to weekly, and choose the weekday and time you inject; Pepti reminds you then, repeating your own figure in your own unit. It never supplies one.
Then add your supply. The approved product is a prefilled pen of solution; compounded material is commonly a powder that needs reconstituting, as the reference page sets out. Pepti handles both, but differently.
| In the app | Prefilled pen | Compounded vial |
|---|---|---|
| What arrives | Solution at the strength printed on the label | Commonly a powder you reconstitute yourself |
| One-time setup | Enter the label strength; there is no mixing step | Enter the peptide in the vial, the water you add and the date you mix it |
| Each week | Day, time, site and the figure you were given | The same, linked to the vial it came from |
| Dates kept | The expiry printed on the pen | The mixing date and the expiry or use-by date you enter |
The app does not do reconstitution arithmetic; for that, the free reconstitution calculator on this site works out the concentration, the volume to draw and the U-100 syringe units in your browser. Concentration varies between compounded preparations, so each new vial gets its own record rather than inheriting the last one’s.
What to log each week
- Day and clock time — weekly drift happens a few hours at a time and only shows up in the record.
- The figure you were given — in the unit you think in. Pepti records it; it never calculates or suggests what it should be.
- Which pen or vial — so a fresh pen or newly mixed vial is never confused with the last.
- Injection site — one of twelve, chosen with the record of where recent injections went.
- What you noticed — a short note or a side-effect entry. Pepti stores these; it does not score or interpret them.
- Weight — ideally the same morning each week, so readings are comparable.
If a week is missed or moved, log that too; a recorded gap is worth more later than a tidy record that hides it. What to do about it is a question for whoever directs your use.
Rotation over a weekly cadence
Rotation is the one area where weekly is harder than daily. Pepti uses twelve sites — abdomen, thigh, deltoid, glute, love handle and tricep, each left and right — and at one injection a week, using all twelve would take around three months. Nobody remembers that far back, so rotation by memory settles on whichever spots are convenient. When you log, Pepti suggests a site you have not used recently, on the opposite side from the last one, and its site view shows which areas you have been favouring. The injection site rotation guide explains the scheme in full.
Pen and vial dates, and what each one cost
Every pen and vial has dates that matter to the record. Pepti records the expiry you enter and, for a compounded vial, the day you mixed it, and warns as the expiry approaches; how long mixed material stays usable is set by your material’s source, and this page supplies no figure for it.
You can also record what each pen or vial cost. The prices are yours; the app keeps them with the vial and does not work out a cost per injection.
Weight trend: reading a slow line
If weight is the number you are watching, it is also the easiest to misread. Single weigh-ins vary from day to day; readings taken the same way each week are what make the line comparable. Pepti plots weight on the same timeline as the injection log, so a plateau or a steady change sits in context, next to any weeks that were missed or moved.
Keep the scale of the evidence in mind. The trial results quoted for semaglutide are group averages over more than a year (Wilding et al., NEJM 2021, summarised on the reference page); one person’s line over a few weeks is not comparable. The chart shows what you recorded and predicts nothing.
Half-life, and why a missed week shows up
The US label reports an elimination half-life of approximately one week for semaglutide (FDA label, section 12.3), the value our semaglutide page cites. At that length, weekly injections overlap rather than clearing in between. The app does not chart levels; in Pepti a moved or skipped week shows in the dated log itself. The free half-life decay calculator on this site draws a reference curve from a value you enter; it depicts timing, not a measurement of what is in your body or a prediction of response.
Privacy: no account, on your iPhone
A semaglutide record is health data — what you inject, how often, what you weigh — and most trackers keep it on a company server behind an account. Pepti has no account and no sign-up; the log, supply records and weight trend stay on your iPhone. There is no cloud sync. That data leaves your phone only if you turn on the AI coach or lab-report import, both behind one consent switch, and then only your coach messages with the app context they need, or the report you import, are sent to Pepti’s server and processed by Anthropic.
Is Pepti the right semaglutide tracker for you?
Pepti is built around vials: if you reconstitute compounded semaglutide, the vial records and the link from each injection to its vial are its core. If you only inject from prefilled pens, it logs them properly, but a pen-first tracker may suit you better; Pepti vs Shotsy covers that trade-off. Pepti is iOS only, on iOS 17.2 or later; pricing is in the questions below. The wider field is compared, with dated sources, in our peptide tracker comparison; for other weekly compounds see the tirzepatide tracker and GLP-1 tracker pages, and for the basics the peptide tracking app guide.
Sources (3)
- Semaglutide — the US FDA label (section 12.3) states an elimination half-life of approximately 1 week. FDA label (DailyMed)
- Wilding et al., New England Journal of Medicine, 2021 — semaglutide (STEP 1 trial), the group-average result cited on our reference page. PubMed 33567185
- US FDA — approval of oral semaglutide tablets for chronic weight management, NDA 218316, December 2025. FDA approval letter
Common questions
What is a semaglutide tracker app?
A semaglutide tracker app is a record-keeping tool for a weekly injection routine. It stores the day and time of each injection, the site, whether it came from a prefilled pen or a compounded vial, and what you noticed, so the history does not depend on a week-old memory. Pepti also keeps each pen or vial's lot, reconstitution and expiry dates. It never decides anything medical for you.
Can Pepti remind me on my injection day?
Yes. Set the schedule to weekly and pick the weekday and time, and Pepti reminds you then, showing the figure you entered. It never supplies or changes that figure. It also alerts you as the expiry or use-by date you entered approaches.
What is semaglutide's half-life, and does Pepti use it?
The US FDA label reports an elimination half-life of approximately one week. Pepti does not chart levels; the free half-life decay calculator on this site draws a reference curve from a value you enter. The curve shows timing only, not levels in your body or a prediction of response.
Does Pepti tell me what semaglutide dose to take?
No, nowhere, by design. You enter the figure you were given by whoever directs your use, and Pepti records it with the date, time, injection site and vial. It never suggests, recommends or changes that figure, and this page contains none.
Is my semaglutide data private?
Pepti has no account and no sign-up, and your log, supply records and weight trend stay on your iPhone. There is no cloud sync. That data leaves your phone only if you turn on the AI coach or lab-report import, both behind one consent switch, and then only your coach messages with the app context they need, or the report you import, are sent to Pepti's server and processed by Anthropic.
How much does Pepti cost?
Pepti is $12.99 per month or $49.99 per year in USD, with no free trial; you can cancel anytime. There is one tier and no free version: every feature is included, with nothing gated behind an upgrade, and there are no ads in the app. Your protocol and health logs are not used for advertising; install attribution uses Apple's tracking permission prompt.
Does semaglutide need to be refrigerated?
The US label for semaglutide injection says the pen should be stored in a refrigerator before first use, and that after first use it can be kept at controlled room temperature or in a refrigerator for a stated period. It also says not to use it if it has been frozen. Compounded material follows the instruction from the pharmacy that prepared it. Log the storage statement for whatever you hold.
Can Pepti track compounded semaglutide?
Yes. For a compounded vial you record the peptide in the vial, the water you added, the lot and the date you mixed it; for a vial or pen that arrives in solution, you record the strength printed on its label instead. Each vial is set up on its own, and each injection you log is linked to it. Pepti does not calculate concentrations, draw volumes or syringe units.
If you inject semaglutide weekly on an iPhone and want the vial records, the rotation and the weight trend in one private record, Pepti is built for that. If you are on Android, or a pen-only routine suits a simpler tool, the comparison pages above will point you somewhere better.
Get Pepti on the App StoreThis page describes record-keeping. It does not recommend semaglutide or any other substance, and it provides no dose figure and no schedule. Approved-product dosing is a matter for the product label and for whoever directs your use.
Not medical advice. Pepti is a record-keeping tool, not a medical device.
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