First Month on Microdose Tirzepatide: What 57 Patients Reported

Last updated: September 17, 2026

Written by: Jay Hastings, CEO of PlexusDx, and Jayden Lee, PharmD, EMBA, PlexusDx Medical Director

Jay Hastings is the CEO of PlexusDx, a precision health company focused on genetic testing, blood biomarker insights, and personalized wellness recommendations. He has more than 20 years of experience across healthcare innovation, genomics, laboratory operations, healthcare investing, and strategic finance.

Medically reviewed by: Jayden Lee, PharmD, EMBA

Jayden Lee, PharmD, EMBA, is the PlexusDx Medical Director, with a PharmD and MBA specializing in pharmacogenomics and clinical product development, with a proven ability to bridge the gap between genomic research and practical patient outcomes. Dr. Lee has more than 10 years of professional experience in clinical pharmacy, academia, and research.

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“Average weight loss on tirzepatide first month” is a fair question with a messy answer. Most numbers online come from trials of the FDA-approved product at 2.5 mg and up. This article reports something different: what 57 real patients on a much lower dose reported in their first weeks. Microdosing is not a medical term. In the PlexusDx study it meant a total weekly dose of 1 or 2 mg of injectable tirzepatide, below the usual 2.5 mg starting dose.

What “first month” means here

The study did not weigh people on day 30. It used a window: the latest self-reported weight taken 14 to 35 days after the first dose. The median patient in that window had been on treatment for 21 days, or three weeks. So “first month” is a label of convenience. The honest label is “the 14–35-day window.” Please keep that in mind.

The numbers

Fifty-seven of the 60 patients had a qualifying weight in the 14–35-day window. Their mean weight loss was 2.18% (95% CI 1.61–2.76; n=57; median exposure 21 days), and 6 of 57 lost nothing or gained. The median loss was 1.96%. In pounds, the study’s own mean was 4.4 lb. Twelve of 57 (21.1%) had lost 3% or more. Five of 57 (8.8%) had lost 5% or more.

For scale, the group’s mean starting weight was 205.7 lb (SD 47.6), and the mean starting BMI was 33.3 kg/m² (SD 6.1). All were on compounded injectable tirzepatide with vitamin B12 at a total weekly dose of 1 to 2 mg. Fifty-three of the 60 started at 1 mg a week in total; 7 started at 2 mg a week in total.

Six of 57 did not lose weight

Six of 57 patients (10.5%) had no loss or gained weight in this window. One was at exactly 0% change. Five gained. That is worth saying plainly. An average of 2.18% across 57 people does not mean everyone lost about 2%. Some lost more, some lost less, and some gained.

Checking the number another way

The study also asked: what if we use each person’s first eligible weight instead of their latest? The 14–35-day mean was then 2.03% (n=57). Similar, but not identical. Changing the rule changes the number a little. That is normal in a study built from care records, and it is one reason the authors call the results hypothesis-generating rather than proven.

What happened after the first month

Fewer patients had weights in later windows: 19 in the 36–59-day window and 8 in the 60–89-day window. Their mean losses were larger, but they are smaller groups, and the same person can appear in more than one window. Those results are in microdose tirzepatide results at 3, 7 and 9 weeks.

What this does not mean

It does not mean you will lose 4.4 lb in a month. It does not mean a 1 to 2 mg dose works like a 2.5 mg or higher dose; no higher dose was studied. It does not compare to any trial of the FDA-approved product, and it should not be set next to one. It is a description of 57 people in one program, with self-reported weights and no comparison group. Side effects those patients reported at their first check-in are in side effects people reported at 1 to 2 mg.

About the PlexusDx study

A retrospective, single-organization observational study of adults documented as new to GLP-1 medicines with BMI ≥27 kg/m²; no comparison group; self-reported weights; not a clinical trial; preprint not yet peer reviewed. The records came from the commercial care program that PlexusDx operates. Care was delivered by an independent network of U.S.-licensed clinicians through a state-licensed telehealth platform. The medication was compounded injectable tirzepatide with vitamin B12 at a total weekly dose of 1 to 2 mg, prepared by state-licensed compounding pharmacies operating in FDA-registered facilities. The study was written by Jay Hastings (PlexusDx CEO) and Jayden Lee, PharmD, EMBA (PlexusDx Medical Director). See the PlexusDx microdose tirzepatide study (60 patients, 2026).

The authors’ conclusion, in their words: “Weight loss was observed within the 14–35-, 36–59-, and 60–89-day observation windows among evaluable adults initiating compounded injectable tirzepatide at 1–2 mg/week. These hypothesis-generating observations support prospective comparative study, not conclusions about causality, equivalent dosing, or long-term safety.”

To our knowledge (as of September 2026), the first published patient cohort reporting outcomes for injectable tirzepatide started at 1 to 2 mg a week. The full preprint is on medRxiv: Weight Loss With Microdose Tirzepatide: Real-World Outcomes in Patients Initiating Treatment Below 2.5 mg Weekly (doi:10.64898/2026.09.15.26363172; posted September 17, 2026; CC BY 4.0). It has not yet been peer reviewed.

Competing interests, as stated in the preprint: “Jay Hastings is Chief Executive Officer of PlexusDx. Jayden Lee, PharmD, EMBA, is Medical Director of PlexusDx. PlexusDx operates the commercial care program from which the records analyzed in this study arose. The authors’ roles with PlexusDx constitute potential competing interests. The authors retained responsibility for the study design, analysis, interpretation of results, manuscript preparation, and decision to submit the work for publication. The authors and PlexusDx received no payments or services from any third party related to the submitted work.”

Where PlexusDx fits

PlexusDx offers compounded tirzepatide through its Weight Management Protocols, including the entry-tier Microdose GLP-1 Protocol. You fill out a short intake. A licensed clinician reviews it and decides what, if anything, fits you. The study described here looked back at records. It is not a promise of any result.

This article is educational. PlexusDx offers compounded tirzepatide through its Weight Management Protocols. The GLP-1 & Peptide Pathways Genetic Test analyzes how your genes influence peptide-related biological pathways. It does not recommend, prescribe, or determine which peptides you should use. Consult a qualified healthcare provider before beginning any peptide protocol. Compounded tirzepatide is not an FDA-approved drug product. It is prepared by state-licensed compounding pharmacies under federal compounding rules and is not the same as Zepbound® or Mounjaro®. Zepbound® and Mounjaro® are registered trademarks of Eli Lilly and Company. PlexusDx is not affiliated with or endorsed by Eli Lilly and Company.

Frequently Asked Questions

What is the average weight loss on tirzepatide in the first month at a microdose?

In the PlexusDx study, the mean loss in the 14–35-day window was 2.18% (95% CI 1.61–2.76; n=57; median exposure 21 days), or 4.4 lb by the study’s own mean. The median was 1.96%. This describes one group of 57 patients on 1 to 2 mg a week.

How many patients lost nothing in the first month?

Six of 57 (10.5%) had no loss or gained weight in the 14–35-day window. One stayed at exactly 0% change and five gained. The average hides this spread, which is why the study reports the no-loss count right alongside the mean for every window.

How many lost 5% of their weight in the first month?

Five of 57 (8.8%) had lost 5% or more by their latest weight in the 14–35-day window. Twelve of 57 (21.1%) had lost 3% or more. Most patients in this early window had lost less than 3% of their starting weight at that point.

Is this a 30-day result?

No. The window covers days 14 to 35 after the first dose, and the median patient had been on treatment 21 days. Calling it “the first month” is shorthand. Weights were self-reported at routine care check-ins, not measured on a fixed study day.

Can I compare this to clinical trial results for the FDA-approved product?

No. Trials of the FDA-approved product used measured weights, placebo groups, higher doses and much longer follow-up. The PlexusDx study is a retrospective observational study with self-reported weights and no comparison group. Setting the two side by side would mislead you about both.

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Medical and Editorial Standards

Medical review process: This article was reviewed for medical accuracy, scientific clarity, evidence alignment, and appropriate discussion of genetics, medications, supplements, biomarkers, and health-related claims.

Sources and evidence: PlexusDx educational content is developed using peer-reviewed research, clinical literature, reputable medical references, and, where applicable, public health or regulatory guidance.

Commercial transparency: PlexusDx offers genetic testing, blood biomarker testing, personalized supplement recommendations, and related precision wellness services. Product mentions are intended to help readers understand available options and should not be interpreted as medical advice.

Important disclaimer: PlexusDx educational content is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about medications, supplements, genetic testing, lab testing, or health-related care.