Tirzepatide Units to mg: Dosing in Units on a U-100 Syringe, With Conversion Charts

The direction printed on every one of these vials reads: inject 0.50 mL (50 units) subcutaneously once weekly. Each 2 mL vial holds four weekly doses, one 28-day fill. Tirzepatide is from $159 a month, all-in: medication, physician review, refill management and shipping, with no membership fee. It is compounded by a PCAB-accredited, FDA-registered US 503A pharmacy. Compounded medications are not FDA approved.

Three numbers are involved, and only one of them is the dose.

The conversion runs in two steps:

1. Units to mL: divide the units by 100. 50 units is 0.50 mL. 25 units is 0.25 mL.
2. mL to mg: multiply the mL by the vial concentration. 0.50 mL from a 5 mg/mL vial is 2.5 mg.

Run backwards, the same arithmetic turns a milligram dose into units: mg divided by concentration gives mL, and mL times 100 gives units. For 2.5 mg from a 5 mg/mL vial, that is 2.5 divided by 5, which is 0.50 mL, which is 50 units.

The step people skip is the second one. A unit is a volume mark on a barrel, not an amount of tirzepatide. Fifty units from the 2.5 mg vial and fifty units from the 15 mg vial are the same volume and six times apart in medication. That is why a number of units, on its own, never tells you a dose.

mg per unit at each Pepti concentration

Because 1 unit is 0.01 mL, each unit carries one hundredth of the vial's concentration:

This table is arithmetic, labelled as such. It is useful as a sanity check on a label, not as a menu of doses.

It depends entirely on the vial. From Pepti's 2.5 mg vial, which is 10 mg in 2 mL at 5 mg/mL, 2.5 mg is 0.50 mL, or 50 units. The same 2.5 mg from a vial at a different concentration is a different volume:

Math only. Pepti does not dispense 2.5 mg doses from any vial except the 5 mg/mL one, and nobody should improvise a dose by drawing a calculated volume from a stronger vial. The table exists because people who read "2.5 mg is 50 units" online, then use a vial at another concentration, are exactly the people the FDA has described drawing several times the intended amount.

Why the same dose can be a different number of units

Compounded GLP-1 concentrations differ between pharmacies, and the same pharmacy may make several strengths. A unit count only transfers between two vials if they have the same concentration. That is the whole reason Pepti prints the direction in both mL and units for the specific vial you are sent, with the concentration on the label beside it.

Each of Pepti's six tirzepatide vials is dose-specific. The pharmacy concentrates it so that 0.50 mL delivers exactly the weekly dose on the label, which means the line you draw to is the same at every step.

So when your physician moves you up a step, the pharmacy sends the vial for that step, and you keep drawing to 50 units. Dosing errors are the most common problem the FDA has reported with compounded incretin medications, and a fixed volume removes most of the arithmetic that causes them. The full ladder, with what each step is for, is in the tirzepatide dosing chart.

A new dose means a new vial, never a bigger draw

You never move to a higher dose by drawing more from the vial you have. Drawing 100 units from the 5 mg/mL vial is not "5 mg done carefully"; it is an improvised dose from a vial labelled for a different direction. Until a new vial arrives, the directions on your current vial are the ones that apply. Never change, skip, split or increase your own dose. If you think your dose should change, message your care team.

Is the milligram figure weekly or the whole vial?

The dose figure is weekly; the larger figure is the whole vial. The 15 mg vial holds 60 mg in 2 mL at 30 mg/mL. Each 50-unit draw is one 15 mg weekly dose, and the vial holds four of them. Reading the total contents as the dose is one of the label mistakes the FDA has specifically flagged with compounded vials, because compounders often print the per-mL figure and the total in a different order from manufactured products.

Divide the vial volume by the volume of one dose:

That is true at every strength, which is why tirzepatide refills run every 28 days, one vial per fill. A vial also carries a beyond-use date that runs from first puncture, printed on the label, so a vial is not something to stretch. More on reading labels and doses per vial is in how long does a peptide vial last.

Getting the math right only matters if the draw matches it.

• Use a U-100 insulin syringe. The 100-units-per-mL rule applies only to U-100 syringes.
• Hold the syringe vertical at eye level and read the flat front edge of the plunger tip against the 50 mark, not the raised ring behind it.
• Clear large bubbles. If 3 of your 50 units are air, you have drawn less medication than you read.
• Say the number out loud as you draw, and read the label every time rather than your memory.

Barrel sizes differ, commonly 0.3 mL (30 units), 0.5 mL (50 units) and 1 mL (100 units). A 50-unit draw fills a 0.5 mL barrel to its top line and sits at the halfway mark on a 1 mL barrel. Whichever arrives, read it by number, not by where the plunger "usually" sits. The full walkthrough is in how to inject tirzepatide, and the general rules for syringes are in insulin syringe units explained.

The conversion on this page is not a matter of evidence; it is arithmetic fixed by the U-100 standard and the concentration on the label. What the evidence does cover is the dose ladder itself: the 2.5 mg start, the 2.5 mg steps and the 15 mg weekly maximum come from the approved tirzepatide label, built on large randomized trials of the manufactured product. A compounded vial contains the same molecule at the same weekly doses, but no trial has been run on the compounded preparation, and compounded medications are not FDA approved.

The risk that is specific to compounded vials is the one this page is about. The FDA has documented adverse events, some requiring hospitalization, linked to people measuring and self-administering incorrect doses from compounded GLP-1 vials, and to clinicians miscalculating conversions between milligrams, units and millilitres. Fixed 50-unit draws, directions printed in both mL and units, and the concentration on every label are how Pepti designs around it. Lot test results are published at /quality/lab-results.

Tirzepatide cannot be bought legitimately without a prescription. Products sold "for research use only" have no pharmacy accountable for identity, purity, sterility or concentration, and without a reliable concentration every unit calculation on this page is meaningless. The prescription route:

1. Complete a free online intake covering your history, medications and what you want help with.
2. A physician licensed in your state reviews it, usually within 24 hours.
3. If it is appropriate, a state-licensed, FDA-registered US pharmacy compounds the vial for your dose, with your directions printed on it in mL and units.
4. It ships refrigerated with ice packs, sterile syringes and alcohol prep pads.
5. Your care team stays reachable for side effects and dose questions. Refills run every 28 days, one vial per fill.

Pepti is cash-pay and does not bill insurance. Bloodwork is not required for any Pepti treatment. If your physician wants labs for your care, they'll ask through your account. The step-by-step page is how to get tirzepatide prescribed online, and the molecule itself is covered in what is tirzepatide.