GLP-1 Tracker App for iPhone

By Tessaro Pty Ltd, the maker of Pepti · Reviewed October 2026

This page explains what to track for a weekly GLP-1 — semaglutide, tirzepatide or retatrutide, whether you inject compounded peptide from a vial or a branded prefilled pen — and how to choose a GLP-1 tracker app that fits how you dose. It is written by the maker of Pepti, so read the Pepti-specific parts as a description of our own app; the general advice holds whichever tracker you pick. Nothing here is medical advice, and no dose or schedule is suggested on any page.

What a GLP-1 tracker does

A weekly injection sounds easy to remember and is surprisingly easy to lose track of. Was last week’s shot on Sunday or Monday, which side was it, which vial was it from, and is the scale drifting or holding? A GLP-1 tracker answers those from a record rather than memory: it captures each injection as it happens — the dose you were given, the day, the site, and the vial or pen it came from — and lines your weight and side-effect notes up against the same timeline.

The value is in keeping those jobs together. On paper they drift apart: vial details get lost, rotation becomes a guess, and an expiry date slips past. Pepti is built to be the single log the record, the vial details and the trend all refer back to. None of what it shows is medical advice; it is a record-keeping tool by design.

What to log for a weekly GLP-1

A few fields carry most of the weight, because they are the ones a future question turns on. For a once-weekly GLP-1, these are worth keeping.

Compounded vials vs branded pens

Injectable GLP-1s reach people in two very different forms, and a tracker has to handle both. A branded prefilled pen is premixed to a fixed concentration set by the manufacturer: there is no reconstitution — you confirm the dose, inject, and record the dose delivered. A compounded vial arrives as peptide you reconstitute yourself, which adds a mixing step and some arithmetic before every draw (the free calculator on this site handles the arithmetic), and keeping each vial’s record straight is most of what a vial-based tracker is for. Oral options also now exist: an oral semaglutide tablet was approved by the US FDA for chronic weight management in December 2025 (FDA approval letter), and orforglipron, an oral small-molecule GLP-1 receptor agonist, in April 2026 (FDA announcement); a trial of orforglipron reports a mean body-weight reduction of 11.2 percent at 72 weeks in the highest-dose group against 2.1 percent with placebo (Wharton et al., NEJM 2025). Tablets involve no reconstitution and no injection site; this page is about the injectable forms.

Sources (3)

1. US Food and Drug Administration — approval letter for oral semaglutide tablets for chronic weight management, NDA 218316, December 2025. FDA approval letter
2. US Food and Drug Administration, press announcement, 1 April 2026 — approval of orforglipron for chronic weight management. Read on FDA.gov
3. Wharton S, et al., New England Journal of Medicine, 2025 — orforglipron in adults with obesity (ATTAIN-1). PubMed

The reconstitution maths is a couple of divisions, easier to trust as variables than as a worked example with someone else’s numbers. The concentration of a reconstituted vial is the peptide in it divided by the millilitres of water you added; the volume to draw is the figure you are working to divided by that concentration; the last step converts millilitres to units on a U-100 syringe.

U-100 syringes are the common at-home type, marked zero to one hundred units where the full millilitre is one hundred units. Illustrative conversions only: a draw of 0.1 mL is 10 units; 0.25 mL is 25 units; half a millilitre is 50 units. The figures that matter are yours, off your own vial and the amount you were given, not from this page. The trap worth naming is that changing how much water you add makes every memorised unit count wrong, because the vial has not changed but the concentration has. The free reconstitution calculator on this site does both divisions and the unit conversion in your browser (the Pepti app does not); the longer walk-through of what to draw sets out the same steps. The rule holds throughout: you supply a figure you already have, and the calculator on this site converts it — it never chooses it.

Weekly 12-site rotation

Injecting repeatedly into the same spot is the habit rotation exists to break, and the only way to rotate reliably is to know where the last one went — and with a once-weekly GLP-1, the long gap between shots makes memory a poor guide. Pepti tracks a twelve-site scheme: six body regions — abdomen, thigh, deltoid, glute, love handle and tricep — each split left and right. It remembers your recent sites, shows which are due a rest, and points you at the next one, so rotation is something the record enforces rather than something you hold in your head. The standalone injection site rotation guide explains it in full.

Weight trend and vial records

Weight is the number most people on a GLP-1 are watching, and it reads very differently as a trend than as a scatter of weigh-ins. Logged on the same timeline as your injections, a plateau or a steady decline is visible in context rather than in isolation. Pepti keeps weight, side-effect notes and the injection log on one timeline for that reason — it depicts what you recorded, and makes no prediction about what the scale will do next.

A vial also carries dates a record needs: when it was reconstituted, when it expires and what it cost. Pepti keeps those against each vial and links every injection to the vial it came from; it records what you type and does not work out how much is left or when a vial will run out.

For the dates a pen or vial record should hold, see storage and expiry logging, and before a trip, travelling with a weekly injection.

Half-life: why a GLP-1 is dosed weekly

A once-weekly cadence is possible because these compounds are long-acting. Semaglutide has an elimination half-life of about a week and tirzepatide about five days, each per its FDA label — the figures and their sources are on our semaglutide and tirzepatide pages, with retatrutide alongside them. The app does not chart levels. To see the rise-and-fall pattern, the free half-life decay calculator on this site plots a curve from a half-life you enter, and the compound reference pages gather published figures. The curve depicts timing, not a prediction of how you will respond.

Privacy: no account, on-device

Most trackers are built around an account and a server; your routine lives with the company, and the promise about it takes the form of a privacy policy. For GLP-1 data, which is health data people often would rather not have sitting on someone else’s server, that is worth weighing before you commit. Pepti takes the other approach by construction: there is no account and no sign-up, and your protocol and health data stay on the device. 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. With both off, none of it is held server-side for anyone to lose, sell or hand over. We would rather state those exceptions plainly than imply there are none. For the full account of what stays on the phone and what leaves it, see the private peptide tracker page.

How to choose a GLP-1 tracker

There is no universally best tracker. The honest way to choose a GLP-1 tracker is to decide which few things matter for how you dose, then pick the tool that gets those right. The axis that divides most of the field is supply form: if you inject from branded prefilled pens, a pen-oriented tracker will fit you better than ours; if you reconstitute compounded peptide from vials, you need a record that ties each injection to its vial and keeps the dates for each vial, which is what Pepti is built around. After that it comes down to platform (Pepti is iOS only, iOS 17.2 or later), privacy model (on-device versus account-and-cloud), and whether the app suggests amounts or only records yours.

For the field itself, we keep a disclosed comparison of peptide tracker apps covering which need an account, where data is stored, and each app’s dosing stance, platforms and price. The pen-versus-vial question has its own head-to-head in Pepti vs Shotsy. Every claim about another app there is dated and tied to a public source; this page names no competitor, so nothing here goes stale.

For a single compound, the semaglutide tracker app and tirzepatide tracker app pages cover setup and the weekly entry in more detail. If hair shedding is one of the things you are noting, what the evidence says about hair shedding on GLP-1s is set out on its own page.

Common questions

Is there an app to track GLP-1 injections privately?

Yes. Pepti – Peptide Tracker logs each GLP-1 injection on your iPhone with no account, no sign-up and no cloud sync. Your protocol and health data stays on the device unless you turn on the AI coach or lab-report import, both behind one consent switch; then your coach messages with the app context they need, or the report you import, are sent to Pepti's server and processed by Anthropic. It costs US$12.99 a month or US$49.99 a year and never tells you what dose to take.

What is a GLP-1 tracker app?

A GLP-1 tracker app is a record-keeping tool for a weekly injectable routine. It stores what you did and when - the dose you were given, the day, the injection site, and whether it came from a compounded vial or a prefilled pen - so the history lives in one place instead of in your memory. Pepti also rotates injection sites across 12 zones and keeps the lot and expiry dates for each vial or pen. It never decides anything medical for you.

Can I track compounded semaglutide or tirzepatide from vials?

Yes. This is what Pepti is built for. For a compounded vial you record what it holds, the water you added, the lot and the date you reconstituted it, and each injection you log is linked to that vial. You supply the figure you already have; the app records it and never suggests what the figure should be. Pepti does not calculate concentrations, draw volumes or syringe units; the free reconstitution calculator on this site does that arithmetic.

What should I log for each weekly GLP-1 injection?

At minimum, log the dose you were given, the day, and the injection site. Recording whether it came from a vial or a pen, and for a vial the date you reconstituted it, keeps the record complete. Many people also log weight and any side effects as plain notes on the same timeline, so a trend is readable later instead of reconstructed from memory. Pepti keeps all of this as one sequence rather than scattered notes.

Does Pepti tell me what GLP-1 dose to take?

No, nowhere, by design. You enter a figure you already have and Pepti records it with the date, time, injection site and vial. It never suggests, recommends, or calculates what that figure should be. That is a decision for you and whoever directs your care, and Pepti stays on the record-keeping side of that line.

Does it work with prefilled pens as well as compounded vials?

Yes. A prefilled pen is premixed to a fixed concentration, so there is no reconstitution step - you record the dose it delivered and the day, and rotation and weight tracking work the same way. A compounded vial adds a reconstitution step and its date on top. Pepti is built around vials but logs pens too, so you can switch supply form without starting a new record.

Is my GLP-1 data private, and does it need an account?

There is no account and no sign-up, and your routine and health data stay on the device. 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. With both off, none of it is held on a server for anyone to lose, sell, or hand over.

Is there a free GLP-1 tracker app?

Some GLP-1 trackers are free to start; our comparison page lists which, with the date each was checked. Pepti is paid: $12.99 per month or $49.99 per year in USD, with no free trial. The reconstitution calculator on this site is free to use in a browser.

Can a GLP-1 tracker tell me my exact medication level?

No. An app cannot measure what is in your body, and Pepti does not chart medication levels. The free half-life decay calculator on this site plots a curve from a half-life you enter, which shows timing only. It is not a measurement of your level and not a prediction of how you will respond.

What is the best GLP-1 tracker app?

It depends on how you dose. If you inject from prefilled pens, a pen-oriented tracker will fit you better than ours. If you reconstitute compounded peptide from vials, you need a record that ties each injection to its vial and keeps the dates for each vial, which is what Pepti is built around. Platform and privacy model decide the rest. Our comparison page sets out the trade-offs with dated sources.

If you draw compounded semaglutide or tirzepatide from vials, track on iPhone, and want each injection tied to its vial and your data on the device, Pepti is built for exactly that. If you are on pens or Android, the comparison pages above will point you somewhere that fits better — that is the honest use of this page.

This page describes record-keeping. It does not recommend any compound, dose, or schedule, and Pepti provides no dosing guidance on any page.

Not medical advice. Pepti is a record-keeping tool, not a medical device.

Pepti – Peptide Tracker · Guides · Reviewed October 2026 · Editorial policy · About