Detection and Excretion Profile of Retatrutide in Human Plasma and Urine by LC-HRMS: Implications for Antidoping Analysis.

Carneiro GRA, da Costa Nunes IK, Dos Santos Cardoso GR, Dos Santos PF, Padilha MC, Nogueira FCS, Pereira HMG

Rapid communications in mass spectrometry : RCM1 Dec 2026

PMID42745421PMCIDPMC13578828DOI10.1002/rcm.70179PepBankPUB-42745421

Summary

RationaleRetatrutide (LY3437943) is a novel long-acting triple incretin receptor agonist that targets the glucagon-like peptide-1 receptor (GLP-1R), glucose-dependent insulinotropic polypeptide receptor (GIPR), and glucagon receptor (GCGR). Its pronounced effects on body composition and metabolic health, combined with increasing off-label use among physically active populations, raise concerns about potential misuse in sport. Despite growing clinical interest and anecdotal reports about use among amateur athletes, information on the detection and elimination profile of retatrutide in humans remains unexplored.MethodsA method based on liquid chromatography-high-resolution mass spectrometry (LC-HRMS) dedicated to monitor retatrutide was developed and validated in human plasma and urine in accordance with World Anti-Doping Agency (WADA) criteria. Detection was based on the [M + 3H]³⁺ precursor ion by targeted selected-ion monitoring (t-SIM), with confirmatory analysis via parallel reaction monitoring (PRM) of structurally diagnostic fragment ions. From four retatrutide users who self-administered 2 mg subcutaneously on Days 1 and 7, blood and urine samples were collected at predefined time points following self-administration.ResultsThe method was proved fit-for-purpose regarding selectivity, reliability, robustness, and stability. Limits of detection (LOD) were evaluated using both empirical ≥ 95% detection rate criteria and sigmoidal logistic regression modeling, yielding 6.14 ng/mL in plasma and 2.44 ng/mL in urine. Neither intact retatrutide nor metabolite-derived signals were detected in urine samples throughout the entire collection period, despite systematic application of multiple extraction strategies. Plasma concentration-time profiles exhibited nonmonotonic behavior, consistent with prolonged subcutaneous absorption and depot-like release kinetics following repeated dosing.ConclusionThese findings suggest that plasma represents the appropriate matrix for intact retatrutide detection compared with urine. The extended plasma detection window, approximately 56 days after the first dose, supports plasma-based testing as a suitable analytical strategy for this and related long-acting therapeutic peptides in antidoping testing context.

CC BYText from Europe PMC. Highlighted sentences are the source of results.

Results from this study6

3 results from studies that gave the peptide. 3 results from people.

01HumanObservational studyPharmacokinetics
In four users who self-administered retatrutide, neither intact retatrutide nor metabolite-derived signals were detected in urine during the whole collection period.
In plain wordsIn four people who injected retatrutide themselves, no retatrutide or breakdown signals were found in urine.
Peptide
Retatrutide
Outcome
No significant changeUrinary excretion of intact retatrutide and metabolites
Study
n = 4
Outcome group
Pharmacokinetics · Pharmacology
Studied dose
2 mg · subcutaneous · Days 1 and 7As given in this study (human).
Source sentences
Summary
Neither intact retatrutide nor metabolite-derived signals were detected in urine samples throughout the entire collection period, despite systematic application of multiple extraction strategies.
1 context sentence(design, population, supporting numbers)
Summary · context
A method based on liquid chromatography-high-resolution mass spectrometry (LC-HRMS) dedicated to monitor retatrutide was developed and validated in human plasma and urine in accordance with World Anti-Doping Agency (WADA) criteria.
Show in the study text Report a problemFND-4274542104
02HumanObservational studyPharmacokinetics
In four users who self-administered retatrutide, plasma concentration-time profiles were nonmonotonic, consistent with prolonged absorption and depot-like release after repeated dosing.
In plain wordsIn four people who injected retatrutide themselves, blood levels rose and fell unevenly, in line with slow release after repeated doses.
Peptide
Retatrutide
Outcome
MixedPlasma concentration-time profile
Study
n = 4
Outcome group
Pharmacokinetics · Pharmacology
Studied dose
2 mg · subcutaneous · Days 1 and 7As given in this study (human).
Source sentences
Summary
Plasma concentration-time profiles exhibited nonmonotonic behavior, consistent with prolonged subcutaneous absorption and depot-like release kinetics following repeated dosing.
1 context sentence(design, population, supporting numbers)
Summary · context
A method based on liquid chromatography-high-resolution mass spectrometry (LC-HRMS) dedicated to monitor retatrutide was developed and validated in human plasma and urine in accordance with World Anti-Doping Agency (WADA) criteria.
Show in the study text Report a problemFND-4274542105
03HumanObservational studyPharmacokinetics
In users who self-administered retatrutide, the plasma detection window extended to approximately 56 days after the first dose.
In plain wordsIn people who injected retatrutide themselves, it could be detected in blood for about 56 days after the first dose.
Peptide
Retatrutide
Outcome
Not applicablePlasma detection window
Study
n = 4
Outcome group
Pharmacokinetics · Pharmacology
Studied dose
2 mg · subcutaneous · Days 1 and 7As given in this study (human).
Measurements
Plasma detection window
≈ 56 days
after first dose
Source sentences
Summary
The extended plasma detection window, approximately 56 days after the first dose, supports plasma-based testing as a suitable analytical strategy for this and related long-acting therapeutic peptides in antidoping testing context.
1 context sentence(design, population, supporting numbers)
Summary · context
A method based on liquid chromatography-high-resolution mass spectrometry (LC-HRMS) dedicated to monitor retatrutide was developed and validated in human plasma and urine in accordance with World Anti-Doping Agency (WADA) criteria.
Show in the study text Report a problemFND-4274542106

Studies that did not test the peptide alone3

In this study, Retatrutide was a lab tool or a carrier, part of a mix, or the subject of a lab method. These results are not evidence about taking Retatrutide.

04HumanNot a test of Retatrutide aloneObservational studyOther
An LC-HRMS method for retatrutide in human plasma and urine was fit-for-purpose for selectivity, reliability, robustness and stability.
In plain wordsA lab method to detect retatrutide in human plasma and urine met its quality checks.
Peptide
Retatrutide
Outcome
Not applicableLC-HRMS method validation
Study
n: not reported in source
Outcome group
Analytical methods and detection · Pharmacology
Source sentences
Summary
The method was proved fit-for-purpose regarding selectivity, reliability, robustness, and stability.
1 context sentence(design, population, supporting numbers)
Summary · context
A method based on liquid chromatography-high-resolution mass spectrometry (LC-HRMS) dedicated to monitor retatrutide was developed and validated in human plasma and urine in accordance with World Anti-Doping Agency (WADA) criteria.
In this study, Retatrutide was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Retatrutide.
Show in the study text Report a problemFND-4274542101
05HumanNot a test of Retatrutide aloneObservational studyOther
The LC-HRMS method had a limit of detection of 6.14 ng/mL for retatrutide in plasma.
In plain wordsThe lab method could detect retatrutide in plasma at 6.14 ng/mL.
Peptide
Retatrutide
Outcome
Not applicableLimit of detection in plasma
Study
n: not reported in source
Outcome group
Analytical methods and detection · Pharmacology
Measurements
Limit of detection
6.14 ng/mL
plasma
Source sentences
Summary
Limits of detection (LOD) were evaluated using both empirical ≥ 95% detection rate criteria and sigmoidal logistic regression modeling, yielding 6.14 ng/mL in plasma and 2.44 ng/mL in urine.
1 context sentence(design, population, supporting numbers)
Summary · context
A method based on liquid chromatography-high-resolution mass spectrometry (LC-HRMS) dedicated to monitor retatrutide was developed and validated in human plasma and urine in accordance with World Anti-Doping Agency (WADA) criteria.
In this study, Retatrutide was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Retatrutide.
Show in the study text Report a problemFND-4274542102
06HumanNot a test of Retatrutide aloneObservational studyOther
The LC-HRMS method had a limit of detection of 2.44 ng/mL for retatrutide in urine.
In plain wordsThe lab method could detect retatrutide in urine at 2.44 ng/mL.
Peptide
Retatrutide
Outcome
Not applicableLimit of detection in urine
Study
n: not reported in source
Outcome group
Analytical methods and detection · Pharmacology
Measurements
Limit of detection
2.44 ng/mL
urine
Source sentences
Summary
Limits of detection (LOD) were evaluated using both empirical ≥ 95% detection rate criteria and sigmoidal logistic regression modeling, yielding 6.14 ng/mL in plasma and 2.44 ng/mL in urine.
1 context sentence(design, population, supporting numbers)
Summary · context
A method based on liquid chromatography-high-resolution mass spectrometry (LC-HRMS) dedicated to monitor retatrutide was developed and validated in human plasma and urine in accordance with World Anti-Doping Agency (WADA) criteria.
In this study, Retatrutide was a lab tool or a carrier, part of a mix, or the subject of a lab method. This result is not evidence about taking Retatrutide.
Show in the study text Report a problemFND-4274542103

AI wrote and checked these results. AI can make mistakes, so check important results against the source.

Version history

PepBank keeps every version of the data on this study. Status changes from Retraction Watch, Europe PMC and Crossref are listed with their source.

Version 2Current
9 Oct 2026, 18:17 UTC
Study results updated
Version 1
9 Oct 2026, 03:04 UTC
First added · source update from Europe PMC

Subjects

Terms as the source lists them.

PepBank is a research reference. Talk to a doctor before you use any peptide.