Second Obesity commentary flags evidence gaps in microdosing tirzepatide from multi-dose pens

The journal Obesity has published a second commentary on microdosing tirzepatide, the molecule sold as Mounjaro and Zepbound, from multi-dose pens. The new letter, "Microdosing Tirzepatide in Multi-Dose Pens: Clinical Individualization, Safety, and Evidence Gaps," appeared online on August 9, 2026 ^[1] and follows an earlier commentary in the same journal, "Micro Doses, Macro Potential? Considerations for Microdosing Tirzepatide in Multi-Dose Pens" ^[2].

The letter is by Fernando Vidal-Ostos De Lara, an endocrinologist in the Department of Endocrinology and Nutrition at Hospital Universitario Príncipe de Asturias, Universidad de Alcalá, in Madrid, Spain ^[1]. Obesity lists it as a letter to the editor. It carries no abstract, and it states that no datasets were generated or analyzed for it ^[1]. The journal's publication record shows the manuscript was received and revised on June 11, 2026, accepted June 22, 2026, and posted online August 9, 2026 ^[1].

The earlier commentary runs three pages in Obesity and is by A. B. Lodrigues, A. V. Russell, S. Tungate Lopez and A. M. Komé ^[1][2]. The new letter cites that piece directly, and its reference list points to the Zepbound (tirzepatide) prescribing information, two large trials of the drug at its labeled doses in adults with obesity, a trial of tirzepatide in obstructive sleep apnea, and a published review of off-label prescribing and patient harms ^[1].

Taken together, the two pieces center on what the new letter's title calls "evidence gaps." Multi-dose pens make off-label dose manipulation physically easier to carry out, some patients will do it regardless of guidance, and there is no trial evidence on whether below-label dosing preserves any of the benefits tirzepatide has shown at the doses in its prescribing information ^[1][2].

What is not yet known

The new letter reports no new patient data ^[1]. It contains no figures on how many people split or reduce tirzepatide doses, which doses they use, or what results they see ^[1]. Whether the two commentaries have prompted a clinical trial, a labeling change or any regulatory action has not been reported ^[1][2].

Why it matters for patients

Taking less than the labeled dose of tirzepatide sits outside FDA-approved labeling. The evidence cited in the new letter describes the drug's performance at the doses studied in trials and listed in the prescribing information, not at reduced doses ^[1]. Because below-label dosing has not been tested in trials, patients and their clinicians cannot know from the published record whether a reduced dose delivers part of the weight-loss, blood sugar or sleep apnea benefits seen at labeled doses, none of them, or a different set of side effects ^[1].

Both commentaries also point to a practical shift: pen designs that hold multiple doses make it easier for a patient to take a partial dose without any change in prescription. That means the choice to microdose may happen outside a clinical visit, where no one is tracking it.

The new letter is an opinion and analysis piece, not a study, so it does not add evidence for or against the practice on its own ^[1]. Its contribution is to lay out what is and is not established: the trials of tirzepatide enrolled patients at labeled doses, and no trial in either commentary compared lower doses against those doses ^[1][2].

Anyone weighing a lower-than-labeled dose is making that decision without trial data on whether the benefits carry over at that level ^[1].