The Best Retatrutide Tracker Apps

I write this one differently from the rest of the series, because the honest answer to “what should I track retatrutide with” starts with a question about where you got it.

Where things actually stand

Retatrutide is a triple agonist — it activates the receptors for GIP, GLP-1 and glucagon. The glucagon component is the genuinely new part, and it is the reason the drug has attracted so much attention.

Its phase 2 obesity trial, published in the New England Journal of Medicine in 2023, reported mean weight reduction over 48 weeks larger than anything previously seen in this class. That is a striking result and it deserves the interest it got.

It is also a phase 2 result, in a development programme that is still running. As of this writing there is no approved retatrutide product. Which means one of two things is true if you are taking it.

If you are in a clinical trial

Then you already have a tracking system, and it is not an app.

The study’s own diary is the record that counts. Whether that is an eCOA system, a paper form, or a device the site gave you, it is what the investigators analyse and what the regulatory submission rests on. Complete it exactly as instructed, on the schedule you were given.

A personal log alongside it is reasonable, and I think often genuinely useful — it helps you notice your own patterns and makes your conversations with the study team more precise. Two rules if you keep one:

• Tell the study team you are keeping it. They will not mind. They may want to see it.
• Never let a discrepancy go unreported. If your personal log and the study diary disagree, the study team needs to know, because the trial record has to reflect what actually happened.

The trial protocol will also have you monitoring things a weight-loss app would never prompt for. The glucagon component is associated with increases in heart rate and with effects on hepatic glucose handling that the dual and single agonists do not share in the same way, and trials monitor accordingly. That is exactly why the study’s instruments take priority over anything you download.

If you bought it online

I am going to be plain, and then I am going to stop.

Material sold as retatrutide outside a trial is typically labelled a research chemical and not for human use. Its identity, concentration, purity and sterility have been verified by nobody. There is no way for you to confirm any of them.

We already know what happens when people inject GLP-1 molecules from unlabelled vials at concentrations they have to calculate themselves: units-versus-milligram confusion has put people in emergency departments, with approved molecules of known concentration. Retatrutide bought online has neither.

I would not advise using it, and no tracking app changes that assessment. A meticulous log of an unverified substance is a meticulous log.

If you are going to do it anyway — and people do, and I would rather they were less unsafe than more — then at absolute minimum, do it under the supervision of a clinician who knows, and record the stated concentration and the exact volume drawn every single time, so that if something goes wrong the emergency department has something to work with.

The ranking

With all of the above stated, if you are keeping a personal log:

1. Zenday App

Best overall. (zenday.health)

The one I use — disclosure at the top of the page.

It ranks first here for the same reason as everywhere in this series: the dose is the organising event, so dose, symptoms, food and measurements share one timeline, and your post-dose pattern becomes visible within about two cycles instead of having to be reconstructed from memory. Dose is recorded in milligrams, which is the unit that matters when nothing else about the product is standardised. Protein is the headline number rather than calories.

Where it falls short. Web-based by design, which is good for privacy and costs you native widgets. Smaller food database than MyFitnessPal. And — worth saying explicitly on this page — it is built for approved GLP-1 treatment. It has no trial-protocol features, and it is not a substitute for a study diary.

2. Shotsy

Best minimal injection log.

Fast and focused: dose, date, site, weight. Low friction, which is what keeps a log honest.

Where it falls short. A record rather than an interpreter, and thin on nutrition.

3. Meagain

Best for the adjustment.

Mood and motivation during rapid change. Given the effect sizes reported in the retatrutide trials, anyone in that programme is likely navigating a faster physical change than most people around them will understand.

Where it falls short. Light clinical scaffolding.

4. Cronometer

Best for micronutrients.

Rigorous micronutrient database. On any drug producing a large reduction in food volume, the arithmetic is the same: intake halves, requirements do not.

Where it falls short. No dose or side-effect tracking; high effort per meal.

Summary

None of these are trial instruments. If you are in a study, the study’s diary is the record.

The summary I would give a friend

Retatrutide looks genuinely promising and I am watching the phase 3 programme closely — when it reads out, it will change the trial table and I will update it.

Until then: if you are in a trial, use the study’s system and keep a personal log as a supplement. If you are not in a trial, there is no verified product to take, and I would wait. There are two highly effective approved drugs available now, with years of outcome data behind them, and no version of this is worth injecting something nobody has checked.

Two things to record with dates: every dose in mg, and how many days each symptom lasted after the injection. As orientation, escalation intervals in this class run about 4 weeks, symptoms usually peak in the 1–2 weeks after a step up, protein wants 1.2–1.6 g/kg a day, and a dose is rarely judged fairly before 28 days. With an investigational agent the log is doing something extra: it is your own safety record, in the absence of the post-marketing data that exists for approved drugs. Record symptoms with dates even when they resolve, and read them against the side effects nobody preps you for so the red flags are recognisable rather than retrospective.