Key takeaways
- Units = dose (mg) ÷ concentration (mg/mL) × 100. 2.5 mg at 5 mg/mL is 50 units.
- The label starts at 2.5 mg once weekly and adds 2.5 mg no sooner than every 4 weeks, up to 15 mg.
- The same 2.5 mg can be 12.5 or 50 units. Never reuse a unit count after the vial, water or pharmacy changes.
- Missed dose: within 4 days, take it; after 4 days, skip it. That is the label rule for Zepbound and Mounjaro.
- Compounded tirzepatide is not FDA-approved, and the FDA’s shortage-era compounding allowances ended in early 2025.
How to use the tirzepatide calculator
The calculator turns a tirzepatide dose in mg into the volume to draw, in mL and in U-100 insulin-syringe units. It keeps your numbers in the page link, so you can share the exact result.
- Tirzepatide in the vial (mg). Use the total printed on the label, such as 10, 15, 30 or 60 mg. Branded Zepbound and Mounjaro vials come as a ready-made liquid, and their labels give the volume directly (see pens vs vials).
- Bacteriostatic water added (mL). The diluent volume injected into a powder vial. If you have not mixed it yet, compare 1, 2 and 3 mL and see which puts your dose on a readable mark.
- Dose per injection. Enter it in mg, exactly as prescribed. The presets match the label’s 2.5 mg steps. The tool does not choose a dose.
- Syringe. Pick 0.3, 0.5 or 1 mL. Every U-100 syringe reads 100 units per mL, so the size only changes capacity and how finely it is marked.
- Read the result. Draw to the unit mark shown. Read any warnings, then open Show the math to check each step.
What tirzepatide is
Tirzepatide is a once-weekly injectable peptide that activates two gut-hormone receptors: GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1). It is built on the GIP sequence and carries a fatty acid chain that binds albumin in the blood. That binding gives it an elimination half-life of about 5 days (5 to 6 days in the Zepbound label’s obesity data), which is why it is injected once a week.
It is FDA-approved under two brand names. Mounjaro treats type 2 diabetes in adults and in children 10 and older, and lowers the risk of major cardiovascular events in adults with type 2 diabetes at high risk. Zepbound is approved for weight reduction and long-term maintenance in adults with obesity, or overweight plus a weight-related condition, and for moderate to severe obstructive sleep apnea in adults with obesity. Compounded and “research” tirzepatide are not FDA-approved. Retatrutide, which adds a glucagon receptor, is still investigational; see the retatrutide calculator.
Tirzepatide dosage chart: the label schedule
The Zepbound label starts every patient at 2.5 mg injected under the skin once weekly for 4 weeks. The 2.5 mg dose is for starting treatment only. After 4 weeks the dose rises to 5 mg, and further increases come in 2.5 mg steps “after at least 4 weeks on the current dose.” The maximum is 15 mg once weekly. Mounjaro follows the same 2.5 mg start and 2.5 mg steps, with a 15 mg maximum for adults and 10 mg for children.
In the table, the last column (four weekly doses) equals the strength of the matching branded multi-dose vial or KwikPen.
| Step | Weeks | Weekly dose | Role in the label | Four doses |
|---|---|---|---|---|
| 1 | 1–4 | 2.5 mg | Starting dose only | 10 mg |
| 2 | 5–8 | 5 mg | Step up; maintenance option | 20 mg |
| 3 | 9–12 | 7.5 mg | Step up | 30 mg |
| 4 | 13–16 | 10 mg | Step up; maintenance option | 40 mg |
| 5 | 17–20 | 12.5 mg | Step up | 50 mg |
| 6 | 21 onward | 15 mg | Maximum; maintenance option | 60 mg |
Source: Zepbound and Mounjaro prescribing information, section 2. The label weeks are minimums, not a timetable.
Tirzepatide dosage chart in units
Compounded and research vials are sold as powder, so the concentration depends on how much water is added. The FDA has warned, about compounded semaglutide, that concentrations vary by compounder, so always read the mg/mL for your own vial. The chart converts each label dose into U-100 units at five example concentrations.
| Dose | 5 mg/mL | 10 mg/mL | 15 mg/mL | 20 mg/mL | 30 mg/mL |
|---|---|---|---|---|---|
| 2.5 mg | 50 | 25 | 16.7 | 12.5 | 8.33 |
| 5 mg | 100 | 50 | 33.3 | 25 | 16.7 |
| 7.5 mg | — | 75 | 50 | 37.5 | 25 |
| 10 mg | — | 100 | 66.7 | 50 | 33.3 |
| 12.5 mg | — | — | 83.3 | 62.5 | 41.7 |
| 15 mg | — | — | 100 | 75 | 50 |
— means more than 100 units, the capacity of a 1 mL syringe. Mixes that give each column:5 mg/mL = 5 mg + 1 mL, 10 mg + 2 mL, 15 mg + 3 mL; 10 mg/mL = 5 mg + 0.5 mL, 10 mg + 1 mL, 15 mg + 1.5 mL, 20 mg + 2 mL, 30 mg + 3 mL; 15 mg/mL = 15 mg + 1 mL, 30 mg + 2 mL; 20 mg/mL = 10 mg + 0.5 mL, 20 mg + 1 mL, 30 mg + 1.5 mL, 60 mg + 3 mL; 30 mg/mL = 15 mg + 0.5 mL, 30 mg + 1 mL, 60 mg + 2 mL.
Tirzepatide units to mg: the formula
Units on an insulin syringe measure volume. On a U-100 syringe, 1 unit is 0.01 mL. Two formulas convert between the dose and the mark on the barrel.
Check: 2.5 ÷ 5 × 100 = 50 units.
| Term | Meaning | Where to find it |
|---|---|---|
| Vial (mg) | Total tirzepatide in the vial | Vial or pharmacy label |
| Water (mL) | Bacteriostatic water added | What you or the pharmacy injected |
| C | Concentration after mixing | Calculated, or printed on a liquid vial |
| Units | U-100 syringe mark (0.01 mL each) | Calculated |
Example 1: 10 mg vial, 2 mL water, 2.5 mg
The concentration is 10 ÷ 2 = 5 mg/mL. The volume is 2.5 ÷ 5 = 0.5 mL, which is 50 units. The vial holds 4 doses of 2.5 mg.
Example 2: 15 mg vial, 1.5 mL water, 5 mg
The concentration is 15 ÷ 1.5 = 10 mg/mL. The volume is 5 ÷ 10 = 0.5 mL, or 50 units. The vial holds 3 doses of 5 mg.
Example 3: 60 mg vial, 3 mL water, 15 mg
The concentration is 60 ÷ 3 = 20 mg/mL. The volume is 0.75 mL, or 75 units. From the same vial, 2.5 mg is only 12.5 units, and the vial would hold 24 weekly doses of 2.5 mg, far longer than the 28-day default beyond-use date for a punctured multi-dose vial.
Example 4: units back to mg
You drew 30 units from a 30 mg vial mixed with 3 mL (10 mg/mL). The dose is 30 × 10 ÷ 100 = 3 mg. The reverse peptide calculator does this in one step, and the mg to units calculator goes the other way for any strength.
5 mg/mL (10 mg + 2 mL) · 50 units
10 mg/mL (10 mg + 1 mL) · 25 units
20 mg/mL (20 mg + 1 mL) · 12.5 units
How much BAC water to add to a tirzepatide vial
No water volume is universally correct, and a pharmacy’s instructions come first. The water sets the concentration, which sets the units per dose. Less water gives smaller injections; more water makes small doses easier to read. Aim for your dose to land on a whole mark between about 10 and 100 units. The BAC water calculator works backward from the units you want.
In the tables, — means the dose is more than the vial holds, and >100 means it will not fit a 1 mL syringe in one draw.
How much BAC water for a 10 mg tirzepatide vial?
With 1 mL, a 10 mg vial is 10 mg/mL and 2.5 mg is 25 units. With 3 mL it is 3.33 mg/mL and 2.5 mg is 75 units. It holds 4 doses of 2.5 mg.
| Water | mg/mL | 2.5 mg | 5 mg | 7.5 mg | 10 mg | 12.5 mg | 15 mg |
|---|---|---|---|---|---|---|---|
| 1 mL | 10 | 25 | 50 | 75 | 100 | — | — |
| 1.5 mL | 6.67 | 37.5 | 75 | >100 | >100 | — | — |
| 2 mL | 5 | 50 | 100 | >100 | >100 | — | — |
| 3 mL | 3.33 | 75 | >100 | >100 | >100 | — | — |
How much BAC water for a 15 mg tirzepatide vial?
With 1 mL, a 15 mg vial is 15 mg/mL and 2.5 mg is 16.7 units. With 3 mL it is 5 mg/mL and 2.5 mg is 50 units. It holds 6 doses of 2.5 mg or 1 of 15 mg.
| Water | mg/mL | 2.5 mg | 5 mg | 7.5 mg | 10 mg | 12.5 mg | 15 mg |
|---|---|---|---|---|---|---|---|
| 1 mL | 15 | 16.7 | 33.3 | 50 | 66.7 | 83.3 | 100 |
| 1.5 mL | 10 | 25 | 50 | 75 | 100 | >100 | >100 |
| 2 mL | 7.5 | 33.3 | 66.7 | 100 | >100 | >100 | >100 |
| 3 mL | 5 | 50 | 100 | >100 | >100 | >100 | >100 |
How much BAC water for a 20 mg tirzepatide vial?
With 1 mL, a 20 mg vial is 20 mg/mL and 2.5 mg is 12.5 units. With 3 mL it is 6.67 mg/mL and 2.5 mg is 37.5 units. It holds 8 doses of 2.5 mg or 1 of 15 mg.
| Water | mg/mL | 2.5 mg | 5 mg | 7.5 mg | 10 mg | 12.5 mg | 15 mg |
|---|---|---|---|---|---|---|---|
| 1 mL | 20 | 12.5 | 25 | 37.5 | 50 | 62.5 | 75 |
| 1.5 mL | 13.3 | 18.8 | 37.5 | 56.3 | 75 | 93.8 | >100 |
| 2 mL | 10 | 25 | 50 | 75 | 100 | >100 | >100 |
| 3 mL | 6.67 | 37.5 | 75 | >100 | >100 | >100 | >100 |
How much BAC water for a 30 mg tirzepatide vial?
With 1 mL, a 30 mg vial is 30 mg/mL and 2.5 mg is 8.33 units. With 3 mL it is 10 mg/mL and 2.5 mg is 25 units. It holds 12 doses of 2.5 mg or 2 of 15 mg.
| Water | mg/mL | 2.5 mg | 5 mg | 7.5 mg | 10 mg | 12.5 mg | 15 mg |
|---|---|---|---|---|---|---|---|
| 1 mL | 30 | 8.33 | 16.7 | 25 | 33.3 | 41.7 | 50 |
| 1.5 mL | 20 | 12.5 | 25 | 37.5 | 50 | 62.5 | 75 |
| 2 mL | 15 | 16.7 | 33.3 | 50 | 66.7 | 83.3 | 100 |
| 3 mL | 10 | 25 | 50 | 75 | 100 | >100 | >100 |
How much BAC water for a 60 mg tirzepatide vial?
With 1 mL, a 60 mg vial is 60 mg/mL and 2.5 mg is 4.17 units. With 3 mL it is 20 mg/mL and 2.5 mg is 12.5 units. It holds 24 doses of 2.5 mg or 4 of 15 mg.
| Water | mg/mL | 2.5 mg | 5 mg | 7.5 mg | 10 mg | 12.5 mg | 15 mg |
|---|---|---|---|---|---|---|---|
| 1 mL | 60 | 4.17 | 8.33 | 12.5 | 16.7 | 20.8 | 25 |
| 1.5 mL | 40 | 6.25 | 12.5 | 18.8 | 25 | 31.3 | 37.5 |
| 2 mL | 30 | 8.33 | 16.7 | 25 | 33.3 | 41.7 | 50 |
| 3 mL | 20 | 12.5 | 25 | 37.5 | 50 | 62.5 | 75 |
Pens vs vials: how branded tirzepatide is supplied
The current Zepbound and Mounjaro labels (both revised in August 2026) list four presentations, all ready-made liquids that need no mixing:
- Single-dose pen: a prefilled pen holding one dose in 0.5 mL.
- Single-dose vial: one dose in 0.5 mL, drawn with a new syringe and needle.
- Multi-dose vial: 2.4 mL holding four doses of 0.6 mL each.
- Single-patient-use KwikPen: four doses in 2.4 mL. The label says never to share a KwikPen, even with a new needle.
| Dose | Single-dose pen or vial | mg/mL | Multi-dose vial or KwikPen | mg/mL |
|---|---|---|---|---|
| 2.5 mg | 2.5 mg / 0.5 mL | 5 | 10 mg / 2.4 mL | 4.17 |
| 5 mg | 5 mg / 0.5 mL | 10 | 20 mg / 2.4 mL | 8.33 |
| 7.5 mg | 7.5 mg / 0.5 mL | 15 | 30 mg / 2.4 mL | 12.5 |
| 10 mg | 10 mg / 0.5 mL | 20 | 40 mg / 2.4 mL | 16.7 |
| 12.5 mg | 12.5 mg / 0.5 mL | 25 | 50 mg / 2.4 mL | 20.8 |
| 15 mg | 15 mg / 0.5 mL | 30 | 60 mg / 2.4 mL | 25 |
For vials, the labels call for a syringe “capable of measuring a 0.5 mL or 0.6 mL dose.” On a U-100 scale, 0.6 mL is the 60-unit mark, whatever the strength, because each branded strength has its own concentration. Compounded vials differ: one vial serves several doses, so the unit count changes with each step. For branded products, follow the Instructions for Use.
Missed a dose? The label’s 4-day rule
The Zepbound and Mounjaro labels say:
- Within 4 days (96 hours) of the missed dose, take it as soon as possible.
- More than 4 days late, skip it and take the next dose on your regular day.
- Changing your injection day is fine as long as the two doses are at least 3 days (72 hours) apart.
For example, if you inject on Mondays and remember on Thursday, you are 3 days late: take it Thursday and your next dose the following Monday, which is 4 days later. If you remember on Saturday, 5 days have passed, so skip it. Compounded products carry no FDA-reviewed instructions, so ask your prescriber if you have missed several doses in a row.
How to store tirzepatide
The branded labels share the same basic rules: refrigerate at 2 °C to 8 °C (36 °F to 46 °F), never freeze and do not use a dose that has frozen, and keep it in the original carton away from heat and light.
- Single-dose pens and vials may be kept unrefrigerated, no warmer than 30 °C (86 °F), for up to 21 days. The Zepbound label says not to return them to the refrigerator.
- Multi-dose vials and KwikPens can be stored in the refrigerator or at room temperature once opened. Throw them away after 30 days at room temperature, 30 days after first use, or after 4 weekly doses, even if medicine is left.
- Compounded vials follow the pharmacy’s label. For multi-dose vials without stability data, USP <797> sets a default 28-day beyond-use date after first puncture (see reconstitution storage).
Match the vial to your weekly dose so it runs out before its date. At 2.5 mg a week, a 60 mg vial needs 24 weeks; the doses per vial calculator compares that with the beyond-use date.
Compounded tirzepatide: FDA status and dosing errors
Federal law lets pharmacies copy an approved drug more freely while it is on the FDA shortage list. Tirzepatide came off that list in two steps. The FDA declared the shortage resolved on October 2, 2024, then confirmed it after a re-evaluation in a December 19, 2024 order. Compounders got a grace period:
- 503A pharmacies (state-licensed, patient-specific prescriptions): enforcement discretion ended February 18, 2025.
- 503B outsourcing facilities (larger-scale compounders registered with the FDA): it ended March 19, 2025. A federal court denied a request to block the decision on March 5, 2025.
Today a 503A pharmacy may not compound “essentially copies” of Zepbound or Mounjaro regularly or in inordinate amounts, unless a prescriber documents a change that makes a significant difference for an identified patient. A 503B facility may only compound from bulk tirzepatide if it is on the 503B bulks list or the shortage list, and it is on neither. On April 30, 2026, the FDA proposed formally excluding tirzepatide, semaglutide and liraglutide from the bulks list; comments closed June 29, 2026, and the final decision was still pending when we last checked.
The FDA stresses that compounded drugs are not FDA-approved and are not reviewed for safety, effectiveness or quality before sale. As of May 31, 2026, it had received more than 730 adverse event reports tied to compounded tirzepatide. Its July 2024 alert described patients taking 5 to 20 times their intended dose of compounded semaglutide after confusing units, mL and mg. Tirzepatide vials carry the same risk.
Common tirzepatide dosing mistakes
- Reusing a unit count after changing vials. 50 units is 2.5 mg at 5 mg/mL but 7.5 mg at 15 mg/mL. Recalculate after any change in vial, water or pharmacy.
- Choosing mcg instead of mg. Tirzepatide is dosed in mg; 2.5 mcg is 1,000 times smaller. The calculator flags the tiny draw that results.
- Using a syringe that is too small. 7.5 mg at 10 mg/mL is 75 units, which will not fit a 0.5 mL syringe. The calculator warns when a dose does not fit.
- Using a U-40 syringe. Each U-40 unit is 2.5 times larger than a U-100 unit.
- Assuming a vial holds whole doses. A 10 mg vial gives 1 dose of 7.5 mg with 2.5 mg left over.
- Carrying numbers over from semaglutide. Its label doses (0.25 to 2.4 mg for Wegovy’s escalation) are far smaller, and its vials are mixed differently. Use the semaglutide calculator for it.
Frequently asked questions
How many units is 2.5 mg of tirzepatide?
It depends on the concentration. Divide 2.5 mg by the mg/mL and multiply by 100. At 5 mg/mL (a 10 mg vial with 2 mL of water) it is 50 units. At 10 mg/mL it is 25 units, and at 20 mg/mL it is 12.5 units. The mg to units calculator handles any other strength.
How much bacteriostatic water do I add to a 10 mg tirzepatide vial?
Any volume the vial holds works if you recalculate. With 1 mL the vial is 10 mg/mL and 2.5 mg is 25 units. With 2 mL it is 5 mg/mL and 2.5 mg is 50 units. Follow your pharmacy’s instructions if they name a volume. The BAC water calculator works backward from the units you want.
How much BAC water for 15 mg tirzepatide?
With 1.5 mL, a 15 mg vial is 10 mg/mL, so 2.5 mg is 25 units and 5 mg is 50 units. With 3 mL it is 5 mg/mL and 2.5 mg is 50 units. The water changes the units per dose, never the total mg in the vial.
How do I convert tirzepatide units to mg?
Multiply the units by the concentration in mg/mL and divide by 100. At 10 mg/mL, 30 units is 30 × 10 ÷ 100 = 3 mg. The formula assumes a U-100 syringe. The reverse peptide calculator does this for any vial and water volume.
What is the tirzepatide dose schedule on the FDA label?
The Zepbound label starts at 2.5 mg once weekly for 4 weeks, then 5 mg. Further increases are 2.5 mg steps after at least 4 weeks on the current dose, up to 15 mg once weekly. Weight-reduction maintenance doses are 5, 10 or 15 mg. Mounjaro uses the same steps and 15 mg adult maximum. Your prescriber sets your actual dose.
What happens if I miss a tirzepatide dose?
The Zepbound and Mounjaro labels say to take the missed dose as soon as possible within 4 days (96 hours). If more than 4 days have passed, skip it and take the next dose on your usual day. You can change your injection day if the two doses are at least 3 days (72 hours) apart.
How long does a 60 mg tirzepatide vial last?
At 2.5 mg a week it holds 24 doses, or 24 weeks. At 15 mg a week it holds 4. A compounded multi-dose vial usually has a beyond-use date, and USP defaults to 28 days after first puncture when no stability data exist. The doses per vial calculator shows whether the date arrives first.
Is compounded tirzepatide still allowed?
The FDA declared the tirzepatide shortage resolved in 2024. Its grace periods ended on February 18, 2025 for 503A pharmacies and March 19, 2025 for 503B outsourcing facilities. Pharmacies may still compound for an individual patient in limited cases, such as a documented clinical difference. Compounded tirzepatide is not FDA-approved.
Is 10 units of tirzepatide the same as 10 units of semaglutide?
No. Units measure volume, not drug. 10 units is 0.1 mL, so the mg depends on each vial’s concentration. 10 units of a 10 mg/mL tirzepatide mix is 1 mg; 10 units of a 2.5 mg/mL semaglutide mix is 0.25 mg. See the semaglutide calculator.
Does this calculator recommend a tirzepatide dose?
No. It converts the dose you enter into mL and syringe units, and flags common errors such as a dose that will not fit the syringe. The dosing information on this page is quoted from the FDA labels for Zepbound and Mounjaro. Your prescription and your prescriber decide your dose.
Sources
We check every formula and figure on this page against primary sources. See our editorial policy for how we review content.
- Zepbound (tirzepatide) injection: prescribing information
- Mounjaro (tirzepatide) injection: prescribing information (revised 08/2026)
- FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize
- FDA’s concerns with unapproved GLP-1 drugs used for weight loss
- FDA proposes to exclude semaglutide, tirzepatide, and liraglutide on 503B bulks list
- FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products
Reviewed by the PeptideConvert Editorial Team
Last reviewed . PeptideConvert tools do arithmetic only. They do not recommend a dose, and nothing on this site is medical advice. Always follow the label and your prescriber. Read the full medical disclaimer.