What Is a Microdose of Tirzepatide? 1 to 2 mg, Explained

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.

This article is part of the PlexusDx Education Hub — your resource for evidence-based guidance on Peptides & GLP-1. Browse all Peptides & GLP-1 education

People search “what is considered a microdose of tirzepatide” more than almost any other microdose question. The honest answer is short. 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. This article explains where the 2.5 mg number comes from, what a 1 to 2 mg dose is and is not, and who decides.

The short answer

A microdose of tirzepatide is any total weekly dose below the labeled 2.5 mg starting dose. There is no official cutoff. Different clinics use the word differently. Some mean 1.25 mg. Some mean 1 mg. Some mean staying at 2.5 mg for a long time. When you read the word, ask what number the writer means.

In the PlexusDx study the number was clear. Patients started at a total of 1 or 2 mg per week. Nothing above 2 mg per week counted as microdose exposure in the analysis.

Where 2.5 mg comes from

Tirzepatide is the active ingredient in Zepbound® and Mounjaro®. Per the FDA-approved labels, both start at 2.5 mg once a week. The label calls 2.5 mg a starting dose meant to help the body adjust, not a treatment dose. After four weeks the label steps up to 5 mg, then in 2.5 mg steps as needed, to a maximum of 15 mg a week. Zepbound® and Mounjaro® are registered trademarks of Eli Lilly and Company. PlexusDx is not affiliated with or endorsed by Eli Lilly and Company.

So 2.5 mg is the lowest dose the FDA-approved products come in. A 1 or 2 mg weekly dose is below that. It is not on the label. It only exists through a compounding pharmacy, and only when a licensed prescriber writes for it.

What a 1 to 2 mg dose is not

It is not a different drug. It is the same molecule at a smaller amount. It is not a “weaker version” made by a different process. It is not FDA-approved at that dose, because no company has run the trials the FDA requires at 1 or 2 mg. And it is not a dose you pick yourself. In the PlexusDx program, an independent network of U.S.-licensed clinicians through a state-licensed telehealth platform decided every dose.

It is also not defined by how often you inject. A microdose is about the total for the week. In the PlexusDx study, 53 of 60 patients started at 1 mg once a week. Seven of 60 started at 2 mg a week: four of those took 1 mg twice a week, and three took 2 mg once a week. Read what happens if you take tirzepatide twice a week for more on schedule versus total dose.

Why people ask about it

Most people asking about a microdose want one of three things. They want fewer stomach side effects. They want a lower cost. Or they want to see how their body reacts before taking more. Those are reasonable questions to bring to a prescriber. The prescriber weighs them against your health history, your BMI, and your goals.

What a lower dose does for weight is a separate question. PlexusDx looked back at its own records to describe what happened to 60 patients over 14 to 89 days. That report is on the study page linked below. This article does not repeat those numbers, because a definition should not be mixed up with a result.

Related articles

How the studied program was set up: how the microdose tirzepatide protocol works. Who the study included and who decides: who a microdose start is for. Two older PlexusDx articles also cover this question: Decoding Tirzepatide Dosing and Understanding Tirzepatide Microdosing.

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: “These hypothesis-generating observations support prospective comparative study, not conclusions about causality, equivalent dosing, or long-term safety.” 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.

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 considered a microdose of tirzepatide?

There is no official cutoff. A microdose usually means any total weekly dose below the labeled 2.5 mg starting dose. In the PlexusDx study it meant 1 or 2 mg of injectable tirzepatide per week in total. Always ask what number a clinic means when it uses the word.

Is 1.25 mg of tirzepatide a microdose?

Yes, by the common meaning, because 1.25 mg is below the 2.5 mg starting dose. The PlexusDx study did not test 1.25 mg as its own group, so it cannot say what 1.25 mg does. Patients in that study started at a total of 1 or 2 mg per week.

Is a microdose the same as splitting a dose?

No. A microdose describes the total amount for the week. Splitting describes how many injections deliver it. In the PlexusDx study, four patients took 1 mg twice a week, which is 2 mg a week in total. The study did not compare once-weekly with twice-weekly schedules.

Is a microdose of tirzepatide FDA-approved?

No. The FDA-approved tirzepatide products, Zepbound® and Mounjaro®, start at 2.5 mg a week. Doses below that are not on the label. They are prepared by state-licensed compounding pharmacies when a licensed prescriber writes for them. Compounded drugs are not FDA-approved products.

Who decides if I get a microdose?

A licensed prescriber does. In the PlexusDx program, an independent network of U.S.-licensed clinicians reviews each intake through a state-licensed telehealth platform and chooses the dose, if any. You can ask about a lower start. The clinician weighs your history, BMI, and goals before deciding.

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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.