# Retatrutide tracker for iPhone: units to draw, shot day and what's still active

> Track retatrutide from a vial: reconstitution units, weekly shot countdown, body-map rotation, a 6-day half-life curve and daily check-ins. Peppy is free.

Source: https://peppytracker.com/trackers/retatrutide-tracker/
Last updated: 2026-08-30

Tracking retatrutide means reconstituting a vial, converting your dose to units on an insulin syringe, remembering a weekly shot, rotating sites and logging how you feel, without a product label to lean on. Peppy does the reconstitution math, counts down to shot day, suggests the next site on a body map, draws a half-life curve of what's still active, and ties a daily check-in to every shot.

## What tracking retatrutide actually involves

A retatrutide tracker app has to do the same job as a compounded tirzepatide tracker, with one difference: there is no approved product and no prescribing information. [Retatrutide](https://peppytracker.com/compounds/retatrutide/) (LY3437943) is a triple GIP, GLP-1 and glucagon receptor agonist that Eli Lilly has studied as a once-weekly injection; the phase 2 trial published in the New England Journal of Medicine tested 1 mg, 4 mg, 8 mg and 12 mg once weekly over 48 weeks. Peppy lists it as a research compound in the catalog with a weekly frequency and a half-life, and tracks it without judgement or recommendation.

In practice that means a vial you reconstitute yourself. The dose you were given in mg becomes a number of units on an insulin syringe that depends on how much water you add. Peppy's calculator sits inline in the protocol editor: enter the mg in the vial, the mL of bacteriostatic water, and your dose in mg, and it shows "Draw up N units" on a U-100 syringe, warning if the draw will not fit a 1 mL syringe. Try it for retatrutide:

The dose ladder below is what the Peppy catalog lists for retatrutide, drawn from the doses studied in trials. It is there so the catalog entry has sensible defaults, not as a suggestion; the numbers you use come from whoever is supervising you.

| Retatrutide - catalog dose ladder | Dose |
| --- | --- |
| Step 1 | 1 mg |
| Step 2 | 2 mg |
| Step 3 | 4 mg |
| Step 4 | 8 mg |
| Step 5 | 12 mg |

Dose steps as listed in the Peppy catalog so the picker is fast - **not a recommendation**. Your prescriber sets your dose; Peppy tracks it.

## Shot day, rotation and missed doses

Retatrutide is a weekly subcutaneous shot, and the same 13-site body map applies: four abdomen quadrants, two flanks, two thighs, two upper arms, two glutes, other. Open the log sheet and Peppy marks the suggested site with "last used 7 days ago" under it. If you also run a peptide protocol, rotation is shared across both so two shots never land on one spot in the same week. The [injection site rotation guide](https://peppytracker.com/guides/injection-site-rotation/) explains the order and how to customise it (Pro).

There is no label to quote for a missed retatrutide dose. The GLP-1 pen labels have windows (5 days for semaglutide, 4 days for tirzepatide) and people often ask their supervising clinician what applies; the [missed GLP-1 dose guide](https://peppytracker.com/guides/missed-glp-1-dose/) summarises them. Peppy's part is factual: it computes missed and overdue from your schedule and log, shows the elapsed hours on the Today tab, and lets you log late, skip, or add a past dose from the Calendar without creating duplicates.

## Titration and step-ups

The trial protocols escalated over several weeks, and people using retatrutide typically follow a step-up plan from whoever supervises them. Peppy's titration (Pro) stores that plan as steps with durations. When a step ends the dose advances on the card, in the reminder and on the log sheet, and a marker appears on the weight chart. Because the dose is in units, re-run the calculator whenever you reconstitute a new vial with a different volume of water.

## Side effects and weight

The daily check-in scores nausea, constipation, heartburn, sulfur burps and food noise from 1 to 5 by default, with weight, feelings and a note; add others such as fatigue or injection-site reaction from Settings. Weight can arrive from Apple Health and every weigh-in you enter is written back. The Progress tab (Pro) draws the weight trend with goal and step-up markers, a side-effect heat-map lined up with shot days, and an adherence percentage. The [side-effect tracking guide](https://peppytracker.com/guides/track-glp-1-side-effects-food-noise/) explains how to read the heat-map.

## What's still active

The NEJM phase 2 paper describes retatrutide as having a half-life of about six days, which is why it was dosed weekly. Peppy's catalog uses 144 hours to draw an "Active in your system" curve that decays across the week and steps up with each shot. It is an estimate from the half-life, not a measurement, and it is the quickest way to see what a missed week looks like.

## Frequently asked

### Is there a retatrutide tracker app for iPhone?

Yes. Peppy is a free iPhone retatrutide tracker app. Retatrutide is in the catalog as a weekly vial with a half-life, so you enter the vial, water and dose, get the units to draw, set your shot day and log each shot on a body map.

### How do I calculate retatrutide units?

Enter the vial's mg, the mL of bacteriostatic water you add and your dose in mg. Peppy shows the units on a U-100 syringe and warns if the volume will not fit a 1 mL syringe. It is a unit conversion only; retatrutide is investigational and Peppy makes no dosing suggestion.

### How long does retatrutide stay in your system?

The phase 2 trial in the New England Journal of Medicine describes retatrutide as a once-weekly injection with a half-life of about six days. Peppy's catalog uses 144 hours to draw an 'Active in your system' curve, which is an estimate from the half-life, not a measurement.

### How do I remember my weekly retatrutide shot?

Set the shot day in the protocol and the Today tab counts down. With Pro, Peppy sends a reminder and a missed-dose nudge, and the Next Shot widget logs it from your Lock Screen.

### Can I track retatrutide side effects and weight?

The daily check-in scores nausea, constipation, heartburn, sulfur burps and food noise from 1 to 5 with weight, feelings and a note. The Progress tab (Pro) lines those up against your shot days and step-ups.

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Peppy is a tracking tool, not medical advice. Dose calculations are mathematical conversions only. Always follow your prescriber's instructions and verify every draw-up yourself.

Peppy is a free iPhone app (Pro subscription optional). App Store: https://apps.apple.com/us/app/peptide-tracker-peppy/id6775005514