Dosing › 2.5 mg

2.5 mg of tirzepatide

The starting dose: how long it lasts, how many units it is, and why it is not meant to be the dose that works.

Medical review: pendingUpdated 13 Oct 20263 scientific references

Key facts

  • 2.5 mg is the starting dose, taken weekly for the first 4 weeks. It is not a maintenance dose.
  • From a Zepbound or Mounjaro single-dose vial: 0.5 mL, 50 units; from a multi-dose vial: 0.6 mL, 60 units. Pens deliver the dose themselves, with no syringe.
  • From a compounded vial the units depend on the concentration: 25 units at 10 mg/mL.
  • The label moves everyone to 5 mg after 4 weeks.
2.5 mg5 mg7.5 mg10 mg12.5 mg15 mg

How many units is 2.5 mg?

Only vials are drawn with a syringe. Branded vials fix the volume and change the concentration with the strength; compounded vials fix the concentration, so the units change from vial to vial. The single-dose pen and the KwikPen deliver the dose themselves.

SourceConcentrationVolumeU-100 syringe
Zepbound / Mounjaro single-dose vial5 mg/mL0.5 mL50 units
Zepbound / Mounjaro multi-dose vial4.17 mg/mL0.6 mL60 units
Compounded vial5 mg/mL0.5 mL50 units
Compounded vial10 mg/mL0.25 mL25 units
Compounded vial20 mg/mL0.125 mL12.5 units
ImportantNever take two draws or an extra injection to make up a dose. If a dose does not fit your syringe, use a larger syringe, and check the concentration on every new vial.

Work out your draw in units

Tirzepatide units calculator U-100 insulin syringe
mg
mg/mL
25units · 0.25 mL
How it worksunits = dose ÷ concentration × 100. A branded single-dose vial is always 0.5 mL (50 units) and a multi-dose vial 0.6 mL (60 units). Pens need no syringe.
It does notsuggest a dose or tell you when to increase it. That is your prescriber’s decision.
Your dose card, on one printable page
Filled from the calculator. Add your next step and print. Nothing is sent or stored.
Dose–
Vial–
Draw–
Next step–

Where 2.5 mg sits in the schedule

Tirzepatide starts at 2.5 mg weekly and rises in 2.5 mg steps, no sooner than every four weeks, to a maximum of 15 mg. On the Zepbound label the maintenance doses are 5, 10 and 15 mg for weight management. Which step you are on, and for how long, is your prescriber’s decision.

If you miss a doseThe label says to take it 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. The day can be changed as long as doses are at least 3 days (72 hours) apart.

Getting tirzepatide prescribed

Starting tirzepatide

2.5 mg is taken once a week for the first 4 weeks. The label says it is for starting treatment and is not approved as a maintenance dose. Its job is to let your stomach adjust before 5 mg.

Branded pen or vialPens deliver the new dose themselves. A branded vial keeps its volume, 0.5 mL from a single-dose vial or 0.6 mL from a multi-dose vial; only the strength on the label changes, so the label is what you check.

Side effects at 2.5 mg

Nausea, diarrhoea, vomiting and constipation are the most common, and most frequent after a dose increase. The serious risks are the same at every dose; see side effects.

What is not known

There is no trial result for staying on 2.5 mg, because no trial tested it as a maintenance dose.

Frequently asked questions

Is 2.5 mg a maintenance dose?

Not on the Zepbound label, where the maintenance doses for weight management are 5, 10 and 15 mg.

How many units is 2.5 mg of tirzepatide at 10 mg/mL?

25 units, or 0.25 mL, on a U-100 syringe.

How many units is 2.5 mg from a branded vial?

50 units (0.5 mL) from a single-dose vial and 60 units (0.6 mL) from a multi-dose vial. Every strength comes in the same volume; at 2.5 mg the multi-dose vial holds 4.17 mg/mL. Pens need no syringe.

What if I miss my 2.5 mg dose?

Take it within 4 days (96 hours) of the missed day. After more than 4 days, skip it and take the next dose on your usual day, per the label.

Scientific references

  1. Eli Lilly and Company. ZEPBOUND (tirzepatide) prescribing information. DailyMed, 2026.
  2. Eli Lilly and Company. MOUNJARO (tirzepatide) prescribing information. DailyMed, 2026.
  3. Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). N Engl J Med 2022.

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