GLP-1 Dose Calculator

Use this GLP-1 dose calculator only when the current product is a multi-dose vial and its label states a concentration in mg/mL. Enter the target amount already provided by a licensed prescriber. The tool then converts that mass into a liquid volume and the equivalent marking on a U-100 syringe. It does not create a starting dose, escalation step, maintenance dose, or schedule.

Product format comes first. A prefilled pen, single-dose device, and multi-dose vial are not interchangeable delivery systems. If you select “Prefilled pen,” the calculator stops and directs you back to the product Instructions for Use. A generic U-100 conversion should not be used to recreate a pen setting or withdraw medicine from a pen.

Why GLP-1 vial concentrations must be read each time

“GLP-1” describes a drug class, not one universal concentration. Semaglutide and tirzepatide are different active ingredients, and individual products have their own strengths and delivery formats. Compounded multi-dose vials can also use different concentrations. That means a saved syringe-unit number cannot safely stand in for the mg/mL value printed on the vial currently in hand.

FDA has warned that compounded semaglutide and tirzepatide products may be supplied in varying concentrations and that dosing errors have occurred when patients or clinicians confused milligrams, milliliters, and syringe units. The GLP-1 dose calculator keeps those measurements separate on purpose. Read the concentration from the current label, type it into the concentration field, and keep the unit beside the number when you record the result.

The conversion has two steps

First divide the prescribed target in milligrams by the labeled concentration in milligrams per milliliter. The answer is volume in milliliters. Then multiply that volume by 100 because a U-100 scale has 100 marked units per 1 mL. A purely mathematical example is a 2.5 mg target with a 5 mg/mL concentration: 2.5 divided by 5 equals 0.5 mL, and 0.5 mL equals 50 U-100 units. The example demonstrates the formula; it is not a dose or product instruction.

The same 2.5 mg target would produce a different volume if the label stated a different concentration. At 10 mg/mL, the arithmetic gives 0.25 mL, or 25 U-100 units. Both calculations can be correct because the source concentrations differ. A unit chart made for one concentration cannot be carried over to another vial.

Total vial mass is not the same as mg/mL

Some labels show a total mass for the whole container, such as “10 mg,” without placing a concentration beside it. That number cannot be entered as 10 mg/mL unless the final volume is known to be exactly 1 mL. A vial containing 10 mg in 2 mL has a concentration of 5 mg/mL; 10 mg in 4 mL has a concentration of 2.5 mg/mL. The total mass stays the same while concentration changes with volume.

If the label gives total mg and total mL rather than mg/mL, calculate concentration first with the Peptide Reconstitution Calculator or ask the dispensing pharmacy to confirm it. Do not enter a guessed value into this GLP-1 dose calculator. A correct target divided by an incorrect concentration still produces a precise but unusable result.

Do not use this calculator for prefilled pens

Approved prefilled pens and fixed-dose devices have product-specific strengths, delivered volumes, and operating instructions. Their clicks, windows, selectors, or labeled dose buttons are not U-100 syringe markings. Even if a product contains a GLP-1 medicine, that does not turn the device into a multi-dose vial. Follow the manufacturer’s Instructions for Use and the prescription label instead of translating a pen setting with this page.

The format selector is therefore a safety boundary, not a cosmetic preference. When “Prefilled pen” is selected, there is no volume result to copy. This prevents a precise-looking answer from being shown for a product format the formula was not built to handle.

Keep prescribed dose and conversion math separate

A GLP-1 dosage schedule may depend on the exact medicine, indication, treatment history, adverse effects, missed doses, and a clinician’s judgment. None of that information is available to a browser calculator. This page begins after a target amount has already been established. It answers one narrow question: at the concentration on this vial, what liquid volume represents that stated mass?

If you do not have a prescribed target, do not use example values from this page as a substitute. If the prescription uses a device rather than a vial, use the device instructions. If the target, label, and calculator result appear to conflict, contact the prescriber or dispensing pharmacy rather than changing an input until the output looks familiar.

Read U-100 units as volume

On this page, “units” means the marked volume scale on a U-100 insulin syringe: 1 unit equals 0.01 mL. It does not mean milligrams, biological potency, pen clicks, or an international unit of drug activity. A 20-unit mark always represents 0.2 mL on a genuine U-100 scale, but the GLP-1 mass inside that volume depends entirely on concentration.

Check the syringe packaging and barrel before using any unit result. Syringes can have different capacities and graduation spacing. A calculated decimal can also fall between markings that are visible on the device. The calculator cannot improve a physical syringe’s resolution or decide how a value should be rounded.

A short label-checking routine

Record the medicine name, product format, concentration, prescribed target, and the unit attached to each number. Confirm that concentration is written as mg/mL rather than total mg in the entire vial. Run the division once by hand, then verify that multiplying the displayed mL by 100 reproduces the unit result. Save the source values with the answer; a final number such as “25 units” is not reproducible without its concentration and target.

FDA’s current information on unapproved compounded GLP-1 products describes concentration and measurement concerns in more detail. The source is linked from the related semaglutide and tirzepatide pages on this site. For a medicine-specific explanation, open the Tirzepatide Calculator or the Semaglutide Dose Calculator. Those pages retain product-specific regulatory context while sharing the same mass-to-volume formula.

When another tool is the better fit

Use the mcg to Units Calculator when the target and concentration are written in micrograms rather than milligrams. Use the U-100 Syringe Calculator for a mass-free mL-to-units conversion. The main Peptide Calculator is useful when the vial’s total mass and liquid volume must first be combined to calculate concentration. Choosing the page that matches the information actually printed on the label keeps the calculation short and auditable.