Read your vial · units vs mg · concentration · BUD

GLP-1 Vial Label Reader

Your first compounded semaglutide or tirzepatide vial can be confusing — and getting it wrong is dangerous. Tap any field on the label below to see exactly what it means in plain English, then use the calculator to turn your own vial's numbers into the exact units to draw on a U-100 insulin syringe.

Read your label first

Compounded GLP-1 medications are not FDA-approved, and the single most common dosing error reported in patient communities is confusing syringe units with milligrams. Tap any part of the label below to see exactly what it means. This tool is educational and does not replace your pharmacy's labeled instructions.

Your vial label — tap a field

Prescribed dose → units

What it is: Your weekly dose in mg, and the matching units to draw on a U-100 insulin syringe. 100 units = 1 mL, so 1 unit = 0.01 mL.

Why it matters: ⚠️ The #1 reported error is treating syringe units as milligrams. '12.5 units' is NOT '12.5 mg.' Always convert mg → units using your vial's concentration (use the calculator below).

Decode your own vial

Enter the numbers from your label to see your concentration, the units to draw, and how many doses your vial holds.

DrugVial peptide content (mg)Bacteriostatic water added (mL)Your prescribed dose (mg)

Concentration

2.00 mg/mL

Draw to this mark

12.5 units

Doses per vial

Always verify your vial label and concentration with your prescribing clinician and compounding pharmacy. This calculator is educational and does not replace pharmacy-supplied dosing instructions.
Use only PCAB-accredited or state-regulated compounding pharmacies. As of February 2025 (tirzepatide) and April 2025 (semaglutide), FDA enforcement discretion for compounded GLP-1s has ended; verify your pharmacy's legal status.

12.5 units ≠ 0.25 mg. You draw to the 12.5-unit mark on a U-100 insulin syringe to deliver your 0.25 mg dose. Always confirm against your pharmacy's instructions.

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The one mistake that sends people to the ER

The single most common — and most dangerous — error with compounded GLP-1s is confusing units with milligrams. Your prescribed dose is in milligrams (e.g., 0.25 mg). The markings on a U-100 insulin syringe are units of volume, not milligrams of drug. Because 100 units = 1 mL, a 0.25 mg dose from a 2 mg/mL vial is only 12.5 units — not “25 units” and definitely not “0.25 of the syringe.” The ISMP flagged this exact confusion in its December 2024 advisory, and the FDA has logged hundreds of dosing-error reports, including documented 5–20× overdoses [1][2].

How to read your vial, field by field

Vial strength (mg) is the total drug in the whole vial, not your dose. A 5 mg vial usually holds many weeks of doses.
Concentration (mg/mL) = vial mg ÷ the bacteriostatic water added. This is the number you use to convert mg to units.
Units to draw = (your mg dose ÷ concentration) × 100. The calculator above does this for you.
Beyond-Use Date (BUD) [3] is when to discard the vial — follow the date printed on your label.
Pharmacy & lot should name a licensed 503A or FDA-registered 503B pharmacy and your batch. No pharmacy or patient name is a red flag [4].

Before you draw any dose

Compounded GLP-1 medications are not FDA-approved, and this tool is educational — it does not replace your pharmacy's labeled instructions or your prescriber's directions. Always verify the concentration on your specific vial, confirm your dose with your provider, and never use a vial past its beyond-use date. Patients with a personal or family history of medullary thyroid carcinoma (MTC) or MEN 2 should not use these medications.

Related tools and guides

GLP-1 reconstitution calculator — full BAC-water + concentration + units math with safety guards
What's in the box? GLP-1 starter kit decoded — every item in your kit, explained
Do you need an ID to buy a GLP-1 online? — how legitimate platforms verify you
Compounded GLP-1 reconstitution & mixing guide — step-by-step walkthrough
Can you still get compounded semaglutide in 2026?
Pharmacy legitimacy lookup — vet the pharmacy that filled your vial
Best compounded semaglutide providers and where to buy semaglutide safely

References

1.Institute for Safe Medication Practices (ISMP). Compounded GLP-1s require extra vigilance — units-vs-milligrams dosing errors (December 2024 advisory). ISMP / ECRI. 2024. https://home.ecri.org/blogs/ismp-news/compounded-glp-1s-require-extra-vigilance
2.U.S. Food and Drug Administration. FDA's concerns with unapproved GLP-1 drugs used for weight loss — dosing-error reports and compounded-product warnings. FDA.gov — Postmarket Drug Safety Information. 2025. https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss
3.United States Pharmacopeia. USP <797> Pharmaceutical Compounding — Sterile Preparations (2023 revision; beyond-use dating). USP General Chapters. 2023. https://www.usp.org/compounding/general-chapter-797
4.Pharmacy Compounding Accreditation Board (PCAB). PCAB Accreditation Standards for Sterile Compounding Pharmacies — how to verify a compounding pharmacy. Accreditation Commission for Health Care. 2024. https://www.achc.org/pharmacy/pcab/