Compounded tirzepatide and Zepbound are the same molecule measured two different ways. Zepbound's label fixes every dose as a whole device volume, so nothing is read on a syringe scale. A compounded vial is dosed in syringe units at whatever concentration the pharmacy chose, and the reader converts. The milligrams can match; the arithmetic between them is where FDA's dosing-error reports begin. This page sets the two side by side on concentration, ladder and vial rules, and states no preference between them.
The label's ladder is on the Zepbound dose chart, and tirzepatide's label doses on tirzepatide dosage. Medibact's Tirzepatide guide covers the molecule.
Status, as FDA states it
Zepbound is approved under NDA 217806 (Drugs@FDA, original approval 2023-11-08). FDA's page on unapproved GLP-1 drugs, content current as of 2026-10-01, says of compounded versions that "compounded drugs are not FDA approved", that the agency "does not review compounded drugs for safety, effectiveness or quality before they are marketed", and that compounded drugs "should only be used in patients whose medical needs cannot be met by an FDA-approved drug". The same page separately warns about products sold "for research purposes" or "not for human consumption", naming tirzepatide among them.
The two dose systems side by side
| Zepbound (label) | Compounded tirzepatide | |
|---|---|---|
| Who sets the amount | the label: 2.5 mg × 4 weeks, then +2.5 mg steps after ≥4 weeks | the prescription |
| Allowed amounts | 2.5, 5, 7.5, 10, 12.5, 15 mg | any figure written |
| Maximum | 15 mg once weekly | none set by a label |
| How the dose is measured | whole device volume, 0.5 or 0.6 mL | syringe units at the vial's concentration |
| Concentration | 5–30 mg/mL (single-dose), 4.17–25 mg/mL (multi-dose, KwikPen) | set by the pharmacy; 5–20 mg/mL on the charts read |
| Multi-dose vial window | 30 days after first use or 4 doses | FDA generally recommends within 28 days of first use |
| Additives | none in the label | some formulations add B vitamins or other ingredients |
The label column is from the Zepbound prescribing information (openFDA version 40, effective 2026-08-28). The compounded column is the absence of a label plus what FDA states; the concentration range is from two compounding-pharmacy chart pages this site read on 2026-10-06 for tirzepatide in units. Formulations with added ingredients are worked through on semaglutide or tirzepatide with B12.
The same milligrams, in units
The label's six strengths converted to U-100 units at the compounded concentrations in circulation, against the fixed volume each Zepbound device uses:
| Amount | Zepbound single-dose | Zepbound multi-dose / KwikPen | 5 mg/mL | 10 mg/mL | 15 mg/mL | 20 mg/mL |
|---|---|---|---|---|---|---|
| 2.5 mg | 0.5 mL (50) | 0.6 mL (60) | 50 | 25 | 16.7 | 12.5 |
| 5 mg | 0.5 mL (50) | 0.6 mL (60) | 100 | 50 | 33.3 | 25 |
| 7.5 mg | 0.5 mL (50) | 0.6 mL (60) | 150 (>1 syringe) | 75 | 50 | 37.5 |
| 10 mg | 0.5 mL (50) | 0.6 mL (60) | 200 (>1 syringe) | 100 | 66.7 | 50 |
| 12.5 mg | 0.5 mL (50) | 0.6 mL (60) | 250 (>1 syringe) | 125 (>1 syringe) | 83.3 | 62.5 |
| 15 mg | 0.5 mL (50) | 0.6 mL (60) | 300 (>1 syringe) | 150 (>1 syringe) | 100 | 75 |
All unit figures are arithmetic by this site (units = mg ÷ mg/mL × 100). Two readings of the table. First, on Zepbound the unit equivalent never changes — 50 or 60 — because the label changes the concentration, not the volume; on a compounded vial the unit count changes with every step. Second, "50 units" means 2.5 mg, 5 mg, 7.5 mg or 10 mg depending on which compounded vial it is read against: the same syringe mark spans a fourfold range in milligrams. A reader moving between the two systems, or between two compounded vials, carries a unit count across at their peril; the milligram figure and the concentration are what transfer. The full two-way chart is on tirzepatide in units, and the general method on mg to units.
What FDA reports about compounded doses
FDA's page describes three kinds of problem that bear on dosing, each in its own words:
- Measurement errors. Reports of adverse events, "some requiring hospitalization", that may be related to dosing errors with compounded injectable semaglutide, resulting from "patients measuring and self-administering incorrect doses" and "in some cases, health care professionals miscalculating doses".
- Doses above the label. Adverse event reports "that may be related to patients prescribed compounded semaglutide or tirzepatide products in doses beyond what is in the FDA-approved drug label", with symptoms including nausea, vomiting, diarrhoea, abdominal pain and constipation.
- Counts. As of 31 May 2026, "more than 730 reports of adverse events associated with compounded tirzepatide" and 990 for compounded semaglutide. FDA adds that pharmacies that are not outsourcing facilities are not required to report, so the counts are "likely" underreported, and that it is not always possible to tell whether an event was caused by the drug.
The page's advice to prescribers is to "be vigilant" when "determining appropriate doses and titration and dosing schedules", and to patients to ask the prescriber or compounder "how to measure and administer the intended dose". FDA's MedWatch programme takes reports from patients and professionals alike.
The multi-dose vial rules compared
Both systems include a vial used across weeks. The Zepbound multi-dose vial is discarded after four weekly doses, 30 days after first use or 30 days at room temperature, whichever comes first, "even if there is medicine left in it". For compounded multi-dose vials FDA states that it "generally recommends that vials containing multiple doses of sterile medications be used within 28 days after the first use because there is an increased risk of contamination", and that a new sterile needle and syringe is used for each dose. How weekly doses divide into a vial of a given size is on doses per vial; how the Zepbound vials are drawn is on the Zepbound vial page.
What this page does not establish
It compares how doses are defined and measured. It does not compare efficacy or safety — no trial has compared a compounded tirzepatide product with Zepbound, and FDA's adverse-event counts are reports, not rates. It does not recommend either, an amount, a concentration or a schedule. Price and access are outside this site's subject.
Sources and dates
Opened 2026-10-14: the ZEPBOUND (tirzepatide) prescribing information via the openFDA drug label API (Eli Lilly, version 40, effective 2026-08-28), sections 2.1, 2.2, 3 and 16; the Drugs@FDA record for NDA 217806; FDA's page FDA's concerns with unapproved GLP-1 drugs used for weight loss (content current as of 2026-10-01). Compounded concentrations as read by this site on 2026-10-06 (two pharmacy chart pages, cited on the tirzepatide units page). Unit figures are arithmetic by this site. Corrections go to the contact page.