How Do Peptide Units, Milligrams, and Syringe Markings Relate?

On a U-100 syringe, units tell you how much liquid you pull. One hundred units equals 1 mL, so 1 unit equals 0.01 mL. Your milligram dose comes from the strength of your vial, and confusion between those numbers led to doses 5 to 10 times the intended amount with compounded semaglutide in reports to the FDA (FDA dosing alert).

What does a unit on the syringe actually mean?

U-100 means the syringe splits 1 mL into 100 equal marks for liquid volume (Rite Aid syringe guide). Ten units equals 0.10 mL, 25 units equals 0.25 mL, and 50 units equals 0.50 mL.

A smaller barrel makes small amounts easier to read. A 0.3 mL barrel holds 30 units, a 0.5 mL barrel holds 50 units, and a 1 mL barrel holds 100 units. Ten units still equals 0.10 mL in any of them.

How do units become a milligram dose?

Milligrams tell you how much drug that liquid holds. You get that number from the concentration printed on your vial as mg per mL.

Divide your units by 100 to get mL, then multiply that mL by the mg per mL. At 2.5 mg per mL, 10 units equals 0.1 mL and holds 0.25 mg, which equals 250 mcg (Rite Aid syringe guide). Mcg means microgram, and you get it by multiplying milligrams by 1,000.

Why does mixing them up cause overdoses?

The FDA described patients told to draw 5 units, or 0.05 mL, who drew 50 units instead and took 10 times the liquid (FDA dosing alert). The agency also described providers who miscalculated milligrams into units. One provider intended 0.25 mg and prescribed 25 units. Patients in these reports received 5 to 10 times the intended dose, and some required hospital care.

Check the mg per mL on your vial and match it to your prescribed mg before you draw. To get a plan with your dose mapped to your syringe, take the quiz.