Drug facts

Does compounded tirzepatide work?

By ·Editor·Reviewed

Quick answer

The molecule does. In SURMOUNT-1 the approved product lowered body weight by 20.9% at 15 mg over 72 weeks, against 3.1% on placebo. What no trial has done is test a compounded preparation, so whether a given vial delivers the same thing depends on what is in it and how it is dosed — and those two are where most reports of it “not working” actually come from.

What the molecule does1

Weight change at week 72 in SURMOUNT-1
SURMOUNT-1, 72 weeksWeight changeLost 5% or more
Tirzepatide 15 mg−20.9%91%
Tirzepatide 10 mg−19.5%89%
Tirzepatide 5 mg−15.0%85%
Placebo−3.1%35%

That was 2,539 adults with obesity and without diabetes, double-blind, against placebo. In type 2 diabetes the effect on weight is consistently smaller, and the trial that matters there measured blood sugar first: in SURPASS-2, glycated hemoglobin fell by 2.01, 2.24 and 2.30 percentage points at 5, 10 and 15 mg.2 The full summaries are on SURMOUNT-1 and SURPASS-2.

What has never been measured5

On the label — Mounjaro / Zepbound

Every figure above was produced with the approved product, made by its manufacturer, at a known dose, under trial supervision.

In a compounded vial

No trial has tested a compounded tirzepatide preparation. FDA puts the gap plainly: unapproved versions “do not undergo FDA’s review for safety, effectiveness and quality before they are marketed.”

That is not a finding that compounded tirzepatide does not work — the molecule is the molecule. It is a narrower point: the evidence you are relying on is about the approved product, and nothing has checked whether a particular pharmacy’s preparation delivers the same dose of the same thing. What a compounded vial is, and what may be in it besides tirzepatide, is set out in what compounded tirzepatide is.

Why it can seem not to work4

It is still the starting dose. The label’s 2.5 mg dose “is for treatment initiation and is not approved as a maintenance dosage”; it lets side effects settle before the dose rises. In SURMOUNT-1 nobody reached the dose their result is attributed to until a 20-week escalation was over. A month at 2.5 mg with little change is not the drug failing — see the dosage chart.

The dose is not the dose you think. A compounded vial’s concentration is set by the pharmacy, so the same milligram dose is a different mark on the syringe from a different vial. FDA has received adverse-event reports it links to exactly this: patients “measuring and self-administering incorrect doses,” and in some cases health care professionals miscalculating them.5 If you have changed seller or vial recently, check the arithmetic in the dose-in-units calculator.

The vial got warm. FDA recommends not using any injectable GLP-1 drug that arrives warm or with insufficient refrigeration, because heat can affect its quality. The approved label’s own limits are in storage and beyond-use dating.

The expectation was an average. A trial mean is not a personal forecast. In SURMOUNT-1, 57% of the 15 mg group lost 20% or more of their body weight — which also means 43% of them did not.1

What happens when it stops3

SURMOUNT-4 answered this directly. After 36 weeks on tirzepatide, 670 adults were randomized to keep taking it or to switch to placebo. Over the next 52 weeks the group that continued lost a further 5.5%; the group switched to placebo regained 14.0%. So a result that fades after a gap in supply, a lapsed subscription or a change of seller may not be the new vial failing — it may be what stopping does. The trial is summarized on SURMOUNT-4.

Where to take it

To the prescriber, with the vial’s label in hand: the concentration, the dose you are drawing, and how long you have been on it. Whether to stay, step up or stop is a clinical decision, and a price index is not in a position to make it. If cost is what is forcing a gap in treatment, that is a problem this site can help with — the cheapest tirzepatide at every dose.

Questions

Does compounded tirzepatide work?
The molecule does: in SURMOUNT-1 the approved product lowered weight by 20.9% at 15 mg over 72 weeks, against 3.1% on placebo. No trial has tested a compounded preparation, so whether a particular vial delivers the same result depends on what is in it and how it is dosed.
Is compounded tirzepatide as effective as Zepbound?
Nobody has measured it. Every efficacy figure for tirzepatide was produced with the approved product, and FDA does not review compounded versions for effectiveness before they are marketed.
Why is compounded tirzepatide not working for me?
The common reasons are that you are still on the 2.5 mg starting dose, which the label approves only for starting treatment, not as a maintenance dose; that the dose is being mismeasured because compounded vials differ in concentration; that the vial was exposed to heat; or that a trial average was read as a personal forecast. A prescriber is the right person to work out which.
How long does compounded tirzepatide take to work?
The label's first four weeks at 2.5 mg are for starting treatment, not a maintenance dose, and in SURMOUNT-1 the dose was escalated over 20 weeks, with results measured at 72. How quickly any one person responds is a question for their prescriber.
What happens if you stop taking compounded tirzepatide?
In SURMOUNT-4, adults who stopped the approved product after 36 weeks regained 14.0% of their weight over the next 52 weeks, while those who continued lost a further 5.5%.

Sources

  1. SURMOUNT-1, New England Journal of Medicine 2022 (PMID 35658024), as summarized on our research page
  2. SURPASS-2, New England Journal of Medicine 2021, as summarized on our research page
  3. SURMOUNT-4, JAMA 2024 (PMID 38078870), as summarized on our research page
  4. FDA prescribing information for ZEPBOUND (tirzepatide), sections 2 and 16, revision 8/2026 DailyMed
  5. FDA, 'FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss', content current as of 09/01/2026 FDA