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Using GLP-1s

U-100 insulin syringe (units)

The small syringe most compounded GLP-1 doses are drawn with — its "units" markings are a volume scale (100 units = 1 mL), not a measure of medication, so converting a mg dose depends entirely on the vial's concentration.

By the glp1.how editorial teamReviewed

A U-100 insulin syringe is the small, fine-needled syringe designed for insulin at a concentration of 100 units per mL. Its barrel is marked in "units," and that scale is really a volume: 100 units = 1 mL, 50 units = 0.5 mL, 10 units = 0.1 mL. The markings say nothing about how much medication is in that volume.

That distinction is a common source of compounded GLP-1 dosing errors. A prescribed dose in milligrams has to be converted to units using the concentration printed on your specific vial (for example, 2.5 mg/mL versus 5 mg/mL), and the same mg dose means a different number of units on each. The FDA has received reports of overdoses, some needing hospital care, that may be tied to people confusing units, mL, and mg (FDA (external link)). If you use a vial and syringe, have your pharmacist confirm the unit count for your dose and concentration. See reading an insulin syringe: units, mL, and mg for compounded GLP-1 doses.

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Updated 1 time since Sep 2, 2026 · show changes
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Related guides

  • Reading an insulin syringe: units, mL, and mg for compounded GLP-1 doses · On a U-100 insulin syringe, "units" measure volume: 100 units make 1 mL. Your vial's concentration is what turns a prescribed mg dose into a unit count. This walkthrough teaches the arithmetic with worked examples at different concentrations, explains the dosing errors the FDA has documented, and gives a checklist to go through with your pharmacist. It teaches you to read the syringe. It does not prescribe doses.
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Related terms

  • GLP-1 · A gut hormone (glucagon-like peptide-1) that stimulates insulin release, slows digestion, and reduces appetite; the target of drugs like semaglutide and liraglutide.

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