Tirzepatide

2.5 mg once a week for 4 weeks, the same start as the Zepbound and Mounjaro labels. Guides then add 2.5 mg every 4 weeks as needed, and some hold each step 6 to 8 weeks to go easier on the stomach.

Usually 3 mL, which gives 10 mg per mL. Some use 2 mL for a stronger 15 mg per mL mix, and 6 mL (5 mg per mL) is used for microdosing. Use the calculator to turn your dose into syringe units for your mix.

No. It is the same molecule. Online shorthand counts generations: semaglutide is "GLP-1", tirzepatide is "GLP-2" because it is a second-generation dual agonist, and retatrutide is "GLP-3". Tirzepatide does not act on the GLP-2 receptor. Real GLP-2 is a separate gut hormone, and its drug version, teduglutide, treats short bowel syndrome. Gray-market sellers put the GLP-2 label on research vials.

Abdomen, thigh or upper arm. The label says exposure is similar at all three, so pick what is comfortable and rotate sites.

Per the label, take it within 4 days (96 hours) of the missed day. If more than 4 days have passed, skip it.

About 28 days in the fridge. Some sellers claim 45 to 60 days, but nobody has shown that. Do not freeze it, and throw it out if it goes cloudy.

Keep them in the fridge at 2 to 8°C. Single-dose pens and vials can stay unrefrigerated at up to 30°C for 21 days in total. Multi-dose vials and the KwikPen hold 4 doses; throw them out after 30 days in use or 4 doses, whichever comes first.

Branded single-dose pens and vials come in 2.5, 5, 7.5, 10, 12.5 and 15 mg per 0.5 mL. Multi-dose vials and KwikPens hold 4 doses of 0.6 mL each, at 10 to 60 mg per 2.4 mL. Compounded pharmacy vials are sold at concentrations such as 5, 10, 17 and 20 mg per mL, and some add niacinamide. Research powder vials run from 10 to 60 mg.

Retatrutide trials show more weight loss: TRIUMPH-1 reported 28.3% at 12 mg over 80 weeks, while SURMOUNT-1 reported 20.9% on tirzepatide 15 mg. Those are different trials, though. The head-to-head trial, TRIUMPH-5, is expected to report in December 2026. Retatrutide is not approved anywhere.

There is no official conversion. One guide waits 7 days after the last tirzepatide shot and starts retatrutide at 2 mg. If nausea is still around, it suggests a 10 to 14 day gap and a 1 mg start. Do not copy your old syringe unit counts, because the mixes differ.

It can. The label advises switching to a non-oral method or adding a backup method for 4 weeks after starting and for 4 weeks after each dose increase.

Vials make it possible, for example 5 mg a week as two 2.5 mg shots 3 to 4 days apart. The argument is that the roughly 5-day half-life gives flatter levels when split. No trial has tested it.

Guides use the word loosely. One telehealth guide calls 0.5 mg or less a microdose and starts at 0.25 mg weekly, adding 0.25 mg every 2 to 4 weeks. Others point to real-world data where most branded users stayed at 2.5 to 7.5 mg. No randomized trial of microdosing exists.

No. WADA does not prohibit it, but it has been on the monitoring program since January 1, 2026. The 2027 list keeps GLP-1 drugs permitted.

Only in narrow cases. FDA ended the shortage in late 2024, and the grace periods ran out on February 18, 2025 for 503A pharmacies and March 19, 2025 for 503B outsourcers. A 503A pharmacy may not make essentially a copy of the branded drug unless there is a documented clinical difference for the patient.

Not always. A public testing aggregator lists 2,845 tirzepatide tests across 277 vendors. Of the 200 most recent visible results, 137 passed and 59 failed.