The short answer: 2.5 mg once a week, borrowed from the Zepbound label. Compounded tirzepatide is made by a pharmacy for you, and FDA doesn't approve it, so it has no label that sets a dose [3]. Prescribers fill that gap with the brand label. For what compounded tirzepatide is and how it's regulated, see our compounded tirzepatide guide.
The label starting dose prescribers use is 2.5 mg once a week
Zepbound is the FDA-approved tirzepatide for weight and sleep apnea. Its label is direct about where to begin:
The recommended starting dosage of ZEPBOUND for all indications is 2.5 mg injected subcutaneously once weekly for 4 weeks. The 2.5 mg dosage is for treatment initiation and is not approved as a maintenance dosage.[1]
Mounjaro, the tirzepatide brand for type 2 diabetes, starts at the same 2.5 mg once weekly [2]. So whichever brand label your prescriber reads, the first month looks the same. The label also says why the start is low: the step-up schedule is there "to reduce the risk of gastrointestinal adverse reactions" such as nausea, vomiting and diarrhea [1].
The label raises the dose in 2.5 mg steps, at least 4 weeks apart
After the first 4 weeks, Zepbound's label moves to 5 mg. From there the dose can rise by 2.5 mg at a time, after at least 4 weeks on the current dose, until a maintenance dose is reached [1]. Your prescriber decides each step, and plenty of people stay at a lower dose that works.
| Weeks | Weekly dose | What the label says |
|---|---|---|
| 1 to 4 | 2.5 mg | Starting dose only; not approved for maintenance |
| 5 onward | 5 mg | The first maintenance option |
| Later, at least 4 weeks per step | 7.5 mg, then 10, 12.5 and 15 mg | Increase in 2.5 mg steps if needed |
| Maintenance for weight | 5, 10 or 15 mg | Chosen by response and tolerability |
| Maintenance for sleep apnea | 10 or 15 mg | Chosen by response and tolerability |
| Maximum | 15 mg | The label's top dose for all uses |
Source: Zepbound prescribing information, DailyMed, version 40. Doses are weekly, in milligrams. Your prescriber sets the actual schedule.
Those maintenance doses are the ones with evidence. In SURMOUNT-1, adults with obesity lost an average of 15.0% of body weight at 5 mg, 19.5% at 10 mg and 20.9% at 15 mg over 72 weeks, against 3.1% on placebo [5]. No arm stayed at 2.5 mg, which is why the label calls it a starting step.
Compounded tirzepatide has no official dose because it has no approval
FDA states that compounded drugs "are not FDA approved," which means the agency doesn't review them for safety, effectiveness or quality before they're sold [3]. There's no compounded tirzepatide label written by FDA. The label on your vial comes from the pharmacy that made it.
Since 2025, pharmacies may compound tirzepatide only for an individual patient, not as routine copies of Zepbound [4]. Your prescription sets the dose, and the pharmacy prepares a vial to match it. If you want the side-by-side on approval, evidence and price, read compounded tirzepatide vs Zepbound.
Your vial's numbers may not match anyone else's
This is the part that trips people up. Compounding pharmacies make tirzepatide at different strengths, so the amount of liquid for the same milligram dose differs from one pharmacy to the next, and sometimes between refills. A volume that's right for one person's vial can be wrong for yours.
That's why you won't find volumes or unit counts here, and why FDA "encourages patients to talk with their health care provider or compounder about how to measure and administer the intended dose" [3]. Ask your pharmacist to show you how your own label translates your prescribed milligrams. Then ask again whenever a refill arrives from a different pharmacy.
Dosing errors are FDA's main worry with compounded vials
FDA has received multiple reports of adverse events, some requiring hospitalization, that may be related to dosing errors with compounded injectable semaglutide. Patients measured incorrect doses, and in some cases health care professionals miscalculated them [3]. The agency also has reports tied to compounded semaglutide or tirzepatide prescribed beyond the approved label: bigger single doses, more frequent doses, or faster increases.
One published case report shows how far a measuring mistake can go. A 50-year-old woman accidentally injected ten times her intended first dose of compounded semaglutide and developed severe swelling of the airway that needed four days on a ventilator [6]. It's a single case, and it's semaglutide, but the mechanism is the same: a vial, a syringe and an unfamiliar label.
Questions to ask before your first dose
- What is my starting dose in milligrams, and is it the label's 2.5 mg?
- How do I measure that dose from this pharmacy's vial? Can the pharmacist show me?
- When will we talk about stepping up, and what would make us wait?
- What should I do if I miss a dose? Zepbound's label allows taking it within 4 days, otherwise skipping it; does that apply to my product?
- Which side effects mean I should call you, and which mean urgent care?
- How long can I use this vial once it's opened?
That last question has an FDA answer for multi-dose vials of sterile medicine: use them within 28 days of first use, even if the compounder's instructions say longer [3]. The guide to compounded tirzepatide out of the fridge covers storage in full.
Switching from Zepbound or Mounjaro is a prescriber decision
If you're moving between brand and compounded tirzepatide, the brand labels offer no conversion for compounded products. Your prescriber chooses whether to restart at a lower step or continue at your current milligram dose, and the pharmacist confirms how that dose is measured from the new vial.
Some people ask about staying below the label doses on purpose. That's a different question, covered in the guide to microdosing tirzepatide. If you haven't chosen a source yet, how to get compounded tirzepatide legally explains what to check first, and is compounded tirzepatide safe? covers the safety record.
See how the 88 compounded tirzepatide providers we score compare on monthly cost and care.