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GLP-1 Dosage Calculator

Turn a prescribed semaglutide or tirzepatide dose in mg into the exact line on a U-100 insulin syringe, with the syringe drawn to scale.

Updated · By Niraj Kumar · 3 sources

Medication

What do you want to work out?What do you want to work out?

Vial strength

What does your vial say?What does your vial say?
mg/mL

Printed on the vial label, e.g. "2.5 mg/mL". Common semaglutide strengths: 1, 2.5, 5 mg/mL.

Your dose

mg

Exactly as written on your prescription. 1 mg is 1,000 mcg.

Dose unitDose unit
Draw to10 units0.1 mL on a U-100 insulin syringe
Dose
0.25 mg
250 mcg
Concentration
2.5 mg/mL
Exact volume
0.1 mL
10 units (1 unit = 0.01 mL on a U-100 syringe)
05101520253010 units
Draw 0.25 mg to the 10 units line of a 0.3 mL (30 units) U-100 syringe.
Semaglutide label doses at 2.5 mg/mLThe FDA-label titration for Wegovy and Ozempic, converted for your vial. Follow the schedule your prescriber gave you.
Weekly doseWhenUnitsmL
0.25 mgWeeks 1–410 units0.1 mL
0.5 mgWeeks 5–820 units0.2 mL
1 mgWeeks 9–1240 units (over capacity)0.4 mL
1.7 mgWeeks 13–1668 units (over capacity)0.68 mL
2.4 mgWeek 17 on (usual maintenance)96 units (over capacity)0.96 mL
7.2 mgOnly if prescribed after 4+ weeks at 2.4 mg288 units (over capacity)2.88 mL

How do you convert mg to units?

Divide your dose in mg by the vial's concentration in mg/mL and multiply by 100. That gives the units to draw on a U-100 insulin syringe. For example, 0.25 mg of semaglutide from a 2.5 mg/mL vial is 0.1 mL, the 10-unit line. If you mixed the vial, its concentration is mg of powder ÷ mL of water.

Dividing the dose by the vial's concentration gives the volume to inject in millilitres. A U-100 insulin syringe has 100 units in every millilitre, so multiplying by 100 turns that volume into the units marked on the barrel. If you mixed the vial yourself, the concentration is the powder's mg divided by the mL of bacteriostatic water you added.

units = dose (mg) ÷ concentration (mg/mL) × 100
dose
Your prescribed dose in mg; 1 mg = 1,000 mcg
concentration
mg of drug per mL of liquid, from the vial label or vial mg ÷ water mL
100
Units per mL on a U-100 insulin syringe
units
The line on the syringe barrel to draw to

Worked example

A 0.5 mg semaglutide dose from a vial labelled 2.5 mg/mL.

  1. 1Volume: 0.5 mg ÷ 2.5 mg/mL = 0.2 mL
  2. 2Units: 0.2 mL × 100 = 20 units

Draw to the 20 units line, on a 0.3 mL (30 units) U-100 insulin syringe.

Frequently asked questions

How do I convert mg to units on an insulin syringe?

Divide your dose in mg by the vial's concentration in mg/mL, then multiply by 100. A 0.5 mg dose from a 2.5 mg/mL vial is 0.5 ÷ 2.5 = 0.2 mL, which is 20 units on a U-100 syringe. The concentration is the number that changes the answer, so check it on every new vial.

Are syringe units the same as mg?

No. Units on an insulin syringe measure volume: on a U-100 syringe, 1 unit is 0.01 mL. How many mg that volume holds depends on the vial's concentration. 20 units of a 2.5 mg/mL vial is 0.5 mg, but 20 units of a 5 mg/mL vial is 1 mg. Mixing these up is the most common cause of reported compounded GLP-1 dosing errors.

What if my dose falls between two lines on the syringe?

Draw to the nearest line; the calculator shows what that line actually delivers. A 1 mL syringe is marked every 2 units, while 0.3 mL and 0.5 mL syringes are marked every unit, so a smaller syringe measures small doses more precisely. If the nearest line is more than 5% off your dose, ask your pharmacy about a smaller syringe or a different vial strength.

How long can I use a mixed or opened vial?

The FDA advises discarding multi-dose vials of compounded GLP-1 drugs 28 days after first use, even if medicine is left. Follow your pharmacy's beyond-use date if it is shorter, keep the vial refrigerated, and use a new sterile needle and syringe for every injection.

Which syringe should I use for compounded GLP-1 doses?

Use the U-100 insulin syringe your pharmacy supplies or names. Choose the smallest one that holds your whole dose: 0.3 mL (30 units) and 0.5 mL (50 units) syringes are marked every unit, while 1 mL (100 units) syringes are marked every 2 units. Never use a U-40 or a non-insulin syringe with these numbers.

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