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Compounded supply

Tirzepatide units to mg: a vial conversion chart

Units are a volume, not a dose: on a U-100 syringe, 100 units is 1 mL. To turn milligrams into units, divide the dose in milligrams by the vial's strength in mg/mL, then multiply by 100. So a 2.5 mg dose is 50 units from a 5 mg/mL vial, 12.5 units from a 20 mg/mL vial and 10 units from a 25 mg/mL vial. That is arithmetic, not a dosing instruction: the dose and the units you draw come from your prescriber and the label on your pharmacy's vial.

J. Merrick · Published · 5 sources · 8 min read

Educational content, not medical advice. Talk to a licensed clinician before starting any treatment.

What this comes down to

  • Units ÷ 100 = milliliters. Milliliters × the vial's mg/mL = milligrams. Without the vial's strength, a number of units says nothing about the dose.
  • The same 2.5 mg is 50 units, 12.5 units or 10 units depending on the vial, across strengths sellers we review list.
  • Zepbound's label starts at 2.5 mg a week for 4 weeks, then steps up by 2.5 mg no sooner than every 4 weeks, to a maintenance dose of 5, 10 or 15 mg. The maximum is 15 mg a week.
  • The FDA has reports of people drawing 5 to 20 times the intended dose from compounded semaglutide vials, with milligrams, milliliters and units mixed up.
Units on a U-100 syringe for the same 2.5 mg dose, by vial strength
  • 5 mg/mL vial (TeleWellnessMD)50 units
  • 20 mg/mL vial (Strut Health)12.5 units
  • 25 mg/mL vial (TeleWellnessMD)10 units
  • Zepbound multi-dose vial, 2.5 mg strength60 units

Same dose, different volume. The compounded strengths are the sellers' own listings; the Zepbound figure is the label's 0.6 mL dose.

How do you convert tirzepatide mg to units?

Three numbers are involved, and they sit on three different things: the dose in milligrams is on your prescription, the strength in mg/mL is on the vial, and the units are on the syringe. A U-100 insulin syringe is marked so that 100 units fill 1 mL. The conversion runs through milliliters:

  1. Milliliters = dose in mg ÷ vial strength in mg/mL.
  2. Units on a U-100 syringe = milliliters × 100.
  3. Worked through: 2.5 mg from a 20 mg/mL vial is 2.5 ÷ 20 = 0.125 mL, which is 12.5 units.
This is arithmetic, not a dosing instruction

Nobody here holds a medical license, and this page does not tell you what to take. Use it to check that the numbers you were given agree with each other. Your dose comes from your prescriber, and the strength comes from the label on the vial your pharmacy sent. If the label, the instructions and this math disagree, call the pharmacy before you inject.

What does a tirzepatide units chart look like?

The chart below runs each Zepbound label dose step through the vial strengths that sellers we review list, as sold by them. TeleWellnessMD lists a "Month 1 2.5mg/0.5mL 2mL Vial" (5 mg/mL) and a "Month 5+ 12.5mg/0.5mL 2mL Vial" (25 mg/mL) for its tirzepatide and B12 blend. Strut Health lists its tirzepatide vials at 20 mg/mL, in 0.5, 1 and 3 mL sizes. Read in September 2026. Other sellers list other strengths, so the column that matters is the one matching your own vial.

Dose5 mg/mL (TeleWellnessMD)20 mg/mL (Strut Health)25 mg/mL (TeleWellnessMD)
2.5 mg50 units (0.5 mL)12.5 units (0.125 mL)10 units (0.1 mL)
5 mg100 units (1 mL)25 units (0.25 mL)20 units (0.2 mL)
7.5 mgover 100 units (1.5 mL)37.5 units (0.375 mL)30 units (0.3 mL)
10 mgover 100 units (2 mL)50 units (0.5 mL)40 units (0.4 mL)
12.5 mgover 100 units (2.5 mL)62.5 units (0.625 mL)50 units (0.5 mL)
15 mgover 100 units (3 mL)75 units (0.75 mL)60 units (0.6 mL)

Units on a U-100 syringe (100 units = 1 mL) for each Zepbound label dose step, at the vial strengths TeleWellnessMD and Strut Health list, read in September 2026. Arithmetic only, not a dose to take.

Two things stand out. At 5 mg/mL, every step above 5 mg is more than 1 mL, which is more than a 1 mL syringe holds. That is why the strength has to rise with the dose: TeleWellnessMD's month 5+ vial is 5 times as strong as its month 1 vial. And at 25 mg/mL, the 2.5 mg starting dose is only 10 units, so a misread mark is a large share of the dose.

When a listing's numbers do not add up

One listing we read in September 2026 prints "5mg / 0.5mg/ml (2ml vial)". Five milligrams in 2 mL would be 2.5 mg per mL, not 0.5, so the strength cannot be worked out from the listing alone, and it is left out of the chart. Another seller's price card says "Start at 20 units a week". Twenty units is 0.2 mL: that is 1 mg at 5 mg/mL, 4 mg at 20 mg/mL and 5 mg at 25 mg/mL. Ask for the vial's strength in writing.

What are the approved tirzepatide dose steps?

Zepbound's prescribing information starts everyone at 2.5 mg once a week for 4 weeks, and says the 2.5 mg dose is for starting only, not a maintenance dose. After 4 weeks the dose goes to 5 mg, and it may rise in 2.5 mg steps after at least 4 weeks on the current dose. The maintenance dose for weight reduction is 5, 10 or 15 mg a week, 10 or 15 mg for obstructive sleep apnea, and the maximum is 15 mg a week[1]. Compounded tirzepatide has no label of its own, so these steps are the reference point, and what each step does to the monthly bill is covered separately.

The brand works the other way round. Zepbound's single-dose pens and vials each hold one dose in 0.5 mL. Its multi-dose vial and KwikPen hold four doses, and every dose is 0.6 mL whatever the strength, because the vial's concentration rises with the dose instead: 4.17 mg/mL for the 2.5 mg vial up to 25 mg/mL for the 15 mg one. The label tells vial users to use a syringe that can measure a 0.5 or 0.6 mL dose[1]. On a U-100 scale, 0.6 mL would read 60 units. With a compounded vial of one strength, the dose climbs and so does the volume.

DoseVial strengthVolume per dose
2.5 mg4.17 mg/mL0.6 mL
5 mg8.33 mg/mL0.6 mL
7.5 mg12.5 mg/mL0.6 mL
10 mg16.7 mg/mL0.6 mL
12.5 mg20.8 mg/mL0.6 mL
15 mg25 mg/mL0.6 mL

Zepbound multi-dose vial, from the prescribing information: the volume per dose stays the same and the strength changes.

Why do units and milligrams get mixed up?

The FDA's 2024 alert on compounded semaglutide describes exactly this. Most reports involved patients drawing more than the prescribed dose from a multi-dose vial, five to 20 times the intended amount; some had been told to draw 5 units and drew 50. Clinicians also miscalculated when converting milligrams to units, in one case prescribing 25 units for a 0.25 mg dose that was 5 units. The FDA said confusion between milliliters, milligrams and units, and the different strengths compounders sell, may have contributed[2]. The same arithmetic applies to tirzepatide, and the semaglutide version of this problem covers the published cases.

The FDA's current page on unapproved GLP-1 drugs also lists reports tied to compounded semaglutide or tirzepatide prescribed beyond the label's doses or stepped up faster than its schedule, and counts more than 730 adverse event reports involving compounded tirzepatide as of May 31, 2026[3]. A study of the FDA's adverse event database found 3,348 accidental overdose reports for GLP-1 drugs, reported disproportionately often for every drug in the class, tirzepatide included[4], and a 2025 case report describes intensive care after unsupervised, rapid dose escalation of tirzepatide[5].

What should you ask the pharmacy before the first dose?

  1. The vial's strength in mg per mL, printed on the label, and whether it matches what the seller's site listed.
  2. Your dose in milligrams and in units, in writing, and which syringe those units assume.
  3. When the vial must be thrown away once opened. Storage and beyond-use dating explains the clock on a multi-dose vial.
  4. Which pharmacy made it. In 2026 the FDA warned dozens of sellers for vial labels showing the seller's name instead; the 2026 warning letters list who received one.

Which sellers we work with list compounded tirzepatide?

Some providers pay us a commission when you sign up through our links, at no extra cost to you. Providers we work with may appear first. Each review covers the vial, the month-two price and the cancellation terms; every seller we price is on the compounded tirzepatide price board, and compounded tirzepatide in 2026 covers the legal status.

Questions people actually ask

How many units is 2.5 mg of tirzepatide?

It depends on the vial's strength. On a U-100 syringe, 2.5 mg is 50 units at 5 mg/mL, 12.5 units at 20 mg/mL and 10 units at 25 mg/mL. Use the number your prescriber and pharmacy label give you.

How many units is 5 mg of tirzepatide?

Again it depends on the vial: 100 units at 5 mg/mL, 25 units at 20 mg/mL and 20 units at 25 mg/mL. Check the strength printed on your own vial.

How do I convert tirzepatide mg to units?

Divide the dose in milligrams by the vial's strength in mg/mL to get milliliters, then multiply by 100 for units on a U-100 syringe. Confirm the result with your pharmacy before injecting.

Is 20 units of tirzepatide a lot?

Twenty units is 0.2 mL, so it depends on the vial: 1 mg at 5 mg/mL, 4 mg at 20 mg/mL and 5 mg at 25 mg/mL. A number of units means nothing without the vial's strength.

What are the approved Zepbound dose steps?

2.5 mg weekly for 4 weeks, then 5 mg, rising by 2.5 mg no sooner than every 4 weeks. Maintenance is 5, 10 or 15 mg a week, and 15 mg is the maximum.

Sources

Every source below was read for this article, with the claim it supports written beside it.

  1. 1.
    ZEPBOUND (tirzepatide) injection, prescribing information. Eli Lilly and Company, via DailyMed (U.S. National Library of Medicine), 2026. Source · Document dated August 2026
    Starting dose 2.5 mg weekly for 4 weeks, not a maintenance dose; increases in 2.5 mg steps after at least 4 weeks; maintenance 5, 10 or 15 mg (10 or 15 mg for OSA); maximum 15 mg weekly. Single-dose pens and vials of 0.5 mL; multi-dose vials and KwikPens of 2.4 mL holding four 0.6 mL doses at 4.17, 8.33, 12.5, 16.7, 20.8 and 25 mg/mL; vial users to use a syringe able to measure a 0.5 or 0.6 mL dose.
  2. 2.
    FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products. U.S. Food and Drug Administration, 2024. Source · Document dated July 2024
    Patients drew five to 20 times the intended dose from multi-dose vials, including 50 units instead of 5; providers miscalculated mg-to-unit conversions, including 25 units for a 0.25 mg (5 unit) dose; confusion between milliliters, milligrams and units and varying compounder concentrations may have contributed.
  3. 3.
    FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. U.S. Food and Drug Administration, 2026. Source · Document dated October 2026
    Adverse event reports that may relate to compounded semaglutide or tirzepatide doses beyond the approved label or faster escalation; more than 730 reports involving compounded tirzepatide as of May 31, 2026.
  4. 4.
    Increased reporting of accidental overdose with glucagon-like peptide-1 receptor agonists: a population-based study. Expert Opinion on Drug Safety, 2026. PMID 39552465 · doi:10.1080/14740338.2024.2430306
    3,348 FAERS reports of accidental overdose with GLP-1 receptor agonists; reporting odds ratios significant for every agent in the class, including tirzepatide.
  5. 5.
    Severe Adverse Effects of Tirzepatide Overdose Requiring Intensive Care Unit Admission and Complex Rehabilitation. Cureus, 2025. PMID 41368024 · doi:10.7759/cureus.98681
    A case of life-threatening complications and a prolonged intensive care stay after unsupervised rapid dose escalation of tirzepatide used for weight loss.

Key figures

Units in 1 mL on a U-100 syringe
100
2.5 mg at 5 mg/mL
50 units
2.5 mg at 25 mg/mL
10 units
Zepbound maximum weekly dose
15 mg