GLP-1 Dose Conversion Chart: mg to Units

To convert a weekly GLP-1 dose into syringe units, divide your milligram dose by the vial concentration in mg/mL to get the volume in mL, then multiply that volume by 100 because a U-100 insulin syringe holds 100 units per mL. For example, a 0.5 mg semaglutide dose from a 2.5 mg/mL vial is 0.5 ÷ 2.5 = 0.2 mL = 20 units.

TL;DR — the one rule that covers every dose

• The formula is always the same: mg ÷ (mg/mL) × 100 = units. It does not change between semaglutide and tirzepatide — only the numbers do.
• Units depend on the vial, not the drug. The same 5 mg tirzepatide dose is 50 units from a 10 mg/mL vial but 25 units from a 20 mg/mL vial.
• A U-100 syringe = 100 units per mL. So 1 mL is 100 units, 0.5 mL is 50 units, 0.1 mL is 10 units. That single fact is what turns mL into the line you read.
• Always confirm against your own label. Compounded concentrations vary by pharmacy; a chart is a sanity check, never a substitute for your vial's stated mg/mL.

Why a milligram dose is not a syringe reading

Prescriptions for semaglutide and tirzepatide are written in milligrams per week — 0.25 mg, 2.5 mg, 5 mg, and so on. But an insulin syringe is not marked in milligrams. It is marked in units, and units measure volume, not mass. A unit on a U-100 syringe is one-hundredth of a millilitre. That mismatch is the entire problem this chart solves: your dose is a mass, your syringe reads a volume, and the bridge between them is the vial's concentration.

Concentration tells you how many milligrams are packed into each millilitre of liquid. A pen or branded auto-injector hides this from you because the device meters the dose. A compounded vial does not — you draw the liquid yourself, so you have to do the conversion yourself. Get the concentration wrong and every unit reading is wrong, which is why the first thing to read is never the dose, but the mg/mL printed on the vial.

How this is calculated

There are only two facts behind every number on this page, and neither is specific to GLP-1 drugs:

1. Concentration is dose per volume. Volume needed (mL) = dose (mg) ÷ concentration (mg/mL).
2. A U-100 syringe is 100 units per mL. Units = volume (mL) × 100.

Chain those together and you get the single rule:

units = mg ÷ (mg/mL) × 100

There is no drug-specific constant, no fudge factor, and no difference between semaglutide and tirzepatide in the maths. The molecules behave differently in your body, but on the syringe they are just a mass dissolved in a volume. Everything below is this one line applied to common doses and concentrations.

Reading units on a U-100 syringe

Before the chart, it helps to see what the units actually look like on the barrel. On a 1 mL U-100 syringe the scale runs 0 to 100; the major numbered marks are usually every 10 units, with a fine line every 1 or 2 units.

The shaded portion above marks a 50-unit (0.5 mL) draw — half the barrel. Most GLP-1 doses sit in the lower half of the syringe, between 5 and 50 units, which is why fine gradations near the start of the scale matter.

Worked examples: dose × concentration → units

Each example below is a distinct combination. Follow the same two steps every time: dose ÷ concentration = mL, then mL × 100 = units.

GLP-1 dose-to-units conversion chart

Common weekly doses for semaglutide and tirzepatide, shown as U-100 syringe units at three concentrations you will actually see on compounded vials. A dash means the draw exceeds 1 mL at that concentration. Confirm every figure against your own vial label.

The cascade of dashes on the right shows why higher tirzepatide doses need higher-concentration vials: 12.5 mg and 15 mg both exceed 1 mL even at 10 mg/mL, so they are typically dispensed at 20 mg/mL or higher (15 mg → 75 units, as in Example 9). If your calculated draw is more than 100 units, your vial is too dilute for that dose — ask your pharmacy, do not split the dose across two jabs.

Common conversion mistakes

The maths is simple, but three errors account for most of the wrong draws people report:

• Reading mg as units. A 2.5 mg dose is not 2.5 units. Milligrams and units are different quantities — you must run the conversion.
• Using the wrong concentration. If you reconstituted the vial yourself with a different amount of water than the label assumed, the mg/mL changed, and so did every unit reading. See the related guide on why the water amount changes your units.
• Forgetting the syringe is U-100. The ×100 step only holds for U-100 syringes. U-40 or U-50 syringes use different scales and are uncommon for these drugs, but if you have one, the multiplier changes.

Frequently asked questions