Vial Guide
Approved drugDual GIP / GLP-1 receptor agonist

Tirzepatide

Active ingredient in Mounjaro and Zepbound

Common dose
2.5 → 15 mg weekly
Cycle
Continuous
Vial sizes
5, 10, 20, 30, 40, 50, 60, 100 mg
Typical draw
10 units50 mg with 2 mL, 2.5 mg

A once-weekly injection that activates both the GIP and GLP-1 receptors, lowering blood sugar and appetite.

Evidence. FDA-approved as Mounjaro (type 2 diabetes in adults and children 10 and older, including lowering heart attack and stroke risk in high-risk adults) and Zepbound (weight management and obstructive sleep apnea).

Status

Approval
Approved in the US as Mounjaro (type 2 diabetes, including heart-risk reduction) and Zepbound (weight management and obstructive sleep apnea).
Sport (WADA 2026)
Not banned in sportNot named on the 2026 list, and S0 does not apply to an approved drug. It was added to WADA’s 2026 Monitoring Program, which tracks use but is not a ban.

Sport status follows the WADA Prohibited List in force since January 1, 2026; athletes should confirm with their anti-doping organization. Checked October 5, 2026.

Protocol

Label

Zepbound / Mounjaro

2.5 mg once weekly for 4 weeks, then 5 mg. Further 2.5 mg steps come after at least 4 weeks on the current dose. Zepbound maintenance is 5, 10 or 15 mg for weight and 10 or 15 mg for sleep apnea; Mounjaro steps up only if blood sugar needs it. Maximum 15 mg (10 mg for children on Mounjaro).

Frequency
Once weekly
Route
Subcutaneous injection
Timing
Same day each week. If you change the day, keep doses at least 3 days apart.
Cycle
Continuous (long-term therapy).

Continuous, shown over 26 weeks

Common protocols

The ways Tirzepatide is most often run, each tagged with where it comes from.

Weight (Zepbound)

Label
Dose
2.5 mg rising to 5, 10 or 15 mg
How often
Once weekly
How long
Long-term

Step up 2.5 mg after at least 4 weeks on each dose. If a dose isn’t tolerated, the label suggests a lower maintenance dose.

Sleep apnea (Zepbound)

Label
Dose
10 or 15 mg
How often
Once weekly
How long
Long-term

Maintenance doses for obstructive sleep apnea with obesity, reached with the same step-up.

Type 2 diabetes (Mounjaro)

Label
Dose
2.5 mg rising to 5–15 mg
How often
Once weekly
How long
Long-term

2.5 mg steps, each after at least 4 weeks, only if more blood-sugar control is needed. Maximum 15 mg in adults, 10 mg in children 10 and older.

Label step-up schedule

PeriodDoseDraw at 25 mg/mL
Weeks 1–42.5 mg10 units (0.10 mL)
Weeks 5–85 mg20 units (0.20 mL)
Weeks 9–127.5 mg30 units (0.30 mL)
Weeks 13–1610 mg40 units (0.40 mL)
Weeks 17–2012.5 mg50 units (0.50 mL)
Week 21 on (maximum)15 mg60 units (0.60 mL)

Units assume a 50 mg vial mixed with 2 mL. Use the calculator for other vial sizes. Zepbound’s maintenance dose for weight is 5, 10 or 15 mg, chosen by response and tolerability. The schedule shows every step up to the 15 mg maximum.

Levels over time

How much of the drug is in the body week by week, worked out from its label half-life of about 5 days. It shows the build-up to a steady level and the fall after the last dose.

0%25%50%75%100% Last dose Week 048121620242832

On the same dose every week, levels reach about 90% of steady state after 3 doses. After the last dose, about 38% is left a week later, and levels fall below 5% after about 4 weeks.

Show the numbers
WeekDose that weekAverage level that week
12.5 mg10%
22.5 mg14%
32.5 mg16%
42.5 mg16%
55 mg27%
65 mg31%
75 mg32%
85 mg33%
97.5 mg44%
107.5 mg48%
117.5 mg49%
127.5 mg50%
1310 mg60%
1410 mg64%
1510 mg66%
1610 mg66%
1712.5 mg77%
1812.5 mg81%
1912.5 mg82%
2012.5 mg83%
2115 mg94%
2215 mg98%
2315 mg99%
2415 mg100%
2515 mg100%
2615 mg100%
2715 mg100%
2815 mg100%
29–38%
30–14%
31–5%
32–2%
33–1%

A simple model: each point is the average level over one week, so it leaves out the rise and dip within the week, and it uses one average half-life, so real levels vary from person to person. 100% is the steady weekly average on the final dose shown. Half-life from the prescribing information.

Taking it

Where it goes

Under the skin of the belly or thigh. Another person can inject the back of the upper arm. Rotate sites with each dose (label).

If you miss a dose

Zepbound label: take it within 4 days (96 hours) of the missed dose. If more than 4 days have passed, skip it and take the next dose on the usual day. Keep doses at least 3 days apart.

What to expect

  1. Weeks 1–4

    2.5 mg is a starter dose to ease in. The label says it is not a maintenance dose.

    Label
  2. Weeks 5–20

    Dose rises 2.5 mg at a time. Most nausea, vomiting and diarrhea happen during these step-ups and fade over time.

    Label
  3. Week 72

    Mean loss 15.0% (5 mg), 19.5% (10 mg) and 20.9% (15 mg) vs 3.1% on placebo. About 57% on 15 mg lost 20% or more.

    Label
  4. After starting and each increase

    Birth-control pills may work less well for 4 weeks. Switch to a non-oral method or add a barrier method.

    Label

Side effects and what to do

Nausea (label: 25–29% vs 8% placebo)

Mostly during step-ups, then fades. Eat smaller meals. If a dose isn’t tolerated, the label suggests a lower maintenance dose.

Diarrhea 19–23%, constipation 11–17%, vomiting 8–13% (label; placebo 8%, 5%, 2%)

Stay hydrated. Heavy fluid loss can cause kidney injury.

Injection-site reactions (label: 6–8% vs 2%)

Rotate sites with each dose.

Hair loss (label: 4–5% vs 1%)

Mention it to your prescriber.

Allergic reactions (label: 5% vs 3%)

Stop and get help right away for face or throat swelling, trouble breathing or fainting.

Stop and get medical help

Severe belly pain that won’t go away (may reach the back), face or throat swelling or trouble breathing, a lump in the neck or trouble swallowing, or pregnancy.

Tracking and pairing

Worth tracking

  • Kidney function if vomiting or diarrhea is heavy
  • Blood sugar if you have diabetes
  • Eye exams if you have diabetic retinopathy
  • Neck lump, hoarseness or trouble swallowing

Often paired with

Usually run on its own.

Human studies

5 key published human studies, with how many people took part. Animal studies aren’t listed here.

  1. 202513,299 people

    Heart attack, stroke or cardiovascular death in 12.2% vs 13.1% on dulaglutide (HR 0.92): noninferior, not superior.

    Design
    Randomized controlled trial vs dulaglutide
    Dose
    Up to 15 mg weekly vs dulaglutide 1.5 mg
    Length
    Median 210 weeks (about 4 years)

    Nicholls et al., N Engl J Med 2025 (SURPASS-CVOT), PMID 41406444

  2. 20222,539 people

    Weight fell 15.0%, 19.5% and 20.9% at 5, 10 and 15 mg vs 3.1% on placebo in adults with obesity without diabetes.

    Design
    Randomized controlled trial
    Dose
    5, 10 or 15 mg weekly
    Length
    72 weeks

    Jastreboff et al., N Engl J Med 2022 (SURMOUNT-1), PMID 35658024

  3. 20211,879 people

    HbA1c fell 2.01 to 2.30 points vs 1.86 with semaglutide 1 mg in type 2 diabetes; all tirzepatide doses were superior.

    Design
    Randomized open-label trial vs semaglutide
    Dose
    5, 10 or 15 mg weekly vs semaglutide 1 mg
    Length
    40 weeks

    Frías et al., N Engl J Med 2021 (SURPASS-2), PMID 34170647

  4. 2025751 people

    Weight fell 20.2% with tirzepatide vs 13.7% with semaglutide in adults with obesity without diabetes.

    Design
    Randomized open-label trial vs semaglutide
    Dose
    10 or 15 mg weekly vs semaglutide 1.7 or 2.4 mg
    Length
    72 weeks

    Aronne et al., N Engl J Med 2025 (SURMOUNT-5), PMID 40353578

  5. 2024469 people

    Apnea-hypopnea index fell 25.3 and 29.3 events per hour vs 5.3 and 5.5 on placebo in adults with sleep apnea and obesity.

    Design
    Two randomized controlled trials
    Dose
    10 or 15 mg weekly
    Length
    52 weeks

    Malhotra et al., N Engl J Med 2024 (SURMOUNT-OSA), PMID 38912654

Mixing your vial

VialWaterCommon doseDrawStrengthAction
5 mg1 mL2.5 mg50 units (0.50 mL)5 mg/mL
10 mg1 mL2.5 mg25 units (0.25 mL)10 mg/mL
20 mg2 mL2.5 mg25 units (0.25 mL)10 mg/mL
30 mg3 mL2.5 mg25 units (0.25 mL)10 mg/mL
40 mg2 mL2.5 mg12.5 units (0.13 mL)20 mg/mL
50 mg2 mL2.5 mg10 units (0.10 mL)25 mg/mL
60 mg3 mL2.5 mg12.5 units (0.13 mL)20 mg/mL
100 mg4 mL2.5 mg10 units (0.10 mL)25 mg/mL

Branded pens and vials are ready-made solutions. Lyophilized vials are mixed with bacteriostatic water; recalculate the units whenever the water volume changes.

Dose chart

Syringe units for common doses at different water volumes. Select a cell to open it in the calculator.

DoseWater added
1 mL2 mL3 mL
2.5 mg
5 mg
7.5 mg
10 mg
12.5 mg
15 mg

U-100 insulin syringe: 100 units is 1 mL. Draws over 100 units show in mL. Faded values are under 2 units, which is hard to measure. Check that your vial holds the larger volumes.

Datasheet

Half-life
about 5 to 6 days LabelSubcutaneous, in adults with overweight or obesity or sleep apnea (Zepbound label); the Mounjaro label states about 5 days.
Type
Peptide, 39 amino acids
Molecular weight
4,813.5 g/mol
Formula
C225H348N48O68
Sequence
YXEGTFTSDYSIXLDKIAQKAFVQWLIAGGPSSGAPPPSX = Aib; Lys20 carries a C20 fatty diacid; C-terminal amide
Storage before use
Not a powder: pens and vials hold a ready-made solution. Refrigerate at 2–8 °C in the carton, away from light; never freeze.
After mixing or opening
Single-dose pens and vials: up to 21 days unrefrigerated (max 30 °C). Multi-dose vial or KwikPen: after first use, fridge or up to 30 °C; discard after 30 days or 4 doses.
  • Half-life: Zepbound and Mounjaro prescribing information rev. 08/2026, section 12.3
  • Molecule: Zepbound label rev. 08/2026 (formula, MW, structure); KEGG D11360 (sequence); PubChem CID 166567236
  • Storage: Label Zepbound prescribing information rev. 08/2026, section 16.2 (Mounjaro rev. 08/2026 gives the same rules)

Cautions

  • Boxed warning for thyroid C-cell tumors (same as semaglutide).
  • Can make birth-control pills less effective for 4 weeks after starting and after each dose increase.
  • GI side effects, pancreatitis, gallbladder disease and dehydration-related kidney injury.
  • Tell the care team before anesthesia or endoscopy (aspiration risk).

Questions

What is tirzepatide?

A once-weekly injection that activates both the GIP and GLP-1 receptors, lowering blood sugar and appetite.

Is tirzepatide FDA-approved?

Approved in the US as Mounjaro (type 2 diabetes, including heart-risk reduction) and Zepbound (weight management and obstructive sleep apnea).

What is the usual tirzepatide dose?

From the label (Zepbound / Mounjaro): 2.5 mg once weekly for 4 weeks, then 5 mg. Further 2.5 mg steps come after at least 4 weeks on the current dose. Zepbound maintenance is 5, 10 or 15 mg for weight and 10 or 15 mg for sleep apnea; Mounjaro steps up only if blood sugar needs it. Maximum 15 mg (10 mg for children on Mounjaro). These are the amounts sources reference, not recommendations.

How much water do I mix tirzepatide with?

There’s no single right amount, because the water only sets the strength. With 2 mL of bacteriostatic water in a 50 mg vial, the strength is 25 mg/mL, so 2.5 mg is 10 units on a U-100 insulin syringe. More water makes small doses easier to measure. The dose chart above shows other volumes.

What is the half-life of tirzepatide?

About 5 to 6 days, according to the prescribing information. Subcutaneous, in adults with overweight or obesity or sleep apnea (Zepbound label); the Mounjaro label states about 5 days.

How should tirzepatide be stored?

Not a powder: pens and vials hold a ready-made solution. Refrigerate at 2–8 °C in the carton, away from light; never freeze. Single-dose pens and vials: up to 21 days unrefrigerated (max 30 °C). Multi-dose vial or KwikPen: after first use, fridge or up to 30 °C; discard after 30 days or 4 doses.

Is tirzepatide banned in sport?

No. Not named on the 2026 list, and S0 does not apply to an approved drug. It was added to WADA’s 2026 Monitoring Program, which tracks use but is not a ban.

Has tirzepatide been studied in people?

Yes. The human studies section lists 5 published studies. The largest, from 2025, included 13,299 people. Heart attack, stroke or cardiovascular death in 12.2% vs 13.1% on dulaglutide (HR 0.92): noninferior, not superior.

Sources

  • Zepbound prescribing information, rev. 08/2026 (Eli Lilly)
  • Mounjaro prescribing information, rev. 08/2026 (Eli Lilly)

By Vial Guide editorsLast reviewed

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