I think my microdose is working. Could I be imagining it?

Some of it, possibly. In SURMOUNT-1 the placebo group lost 2.4% of body weight on average and 28% of them reached 5% loss, without any drug at all. That does not mean nothing is happening on a low dose, but it does mean a modest result is not by itself evidence that the dose is doing the work.

Is there a curve like this for semaglutide?

Not for weight loss. SURMOUNT-1 is the only published maintenance dose-response curve in the class, which is why the same question has a much thinner answer for semaglutide. That page lays out what the STEP programme did and did not randomise.

Once I have lost what I wanted at 5 mg, is there a reason to keep climbing?

The trial answer depends entirely on the target. At the 5% threshold 5 mg and 15 mg are seven points apart, and at 25% they are more than twenty. What the dose should be after goal weight is a separate question that no trial has tested, covered on the maintenance page.

Tirzepatide Microdosing: What SURMOUNT-1 Shows

What this page establishes

SURMOUNT-1 randomised 2,539 participants to tirzepatide 5, 10, 15 mg or placebo for 72 weeks.
Mean weight loss at 72 weeks was 16.0% (5 mg) and 22.5% (15 mg) vs 2.4% placebo; Lilly's published range across doses was 16.0-22.5%.
89% of the 5 mg group and 96% of the 10 and 15 mg groups achieved >=5% weight loss, vs 28% on placebo.
16.5% (5 mg), 35% (10 mg) and 39.7% (15 mg) reached >=25% weight loss vs 0.3% on placebo, i.e. the high-response tail is strongly dose-dependent.

Quick answers

I think my microdose is working. Could I be imagining it?
Some of it, possibly. In SURMOUNT-1 the placebo group lost 2.4% of body weight on average and 28% of them reached 5% loss, without any drug at all.
Read the full answer
That does not mean nothing is happening on a low dose, but it does mean a modest result is not by itself evidence that the dose is doing the work.
Is there a curve like this for semaglutide?
Not for weight loss. SURMOUNT-1 is the only published maintenance dose-response curve in the class, which is why the same question has a much thinner answer for semaglutide.
Read the full answer
That page lays out what the STEP programme did and did not randomise.
Once I have lost what I wanted at 5 mg, is there a reason to keep climbing?
The trial answer depends entirely on the target. At the 5% threshold 5 mg and 15 mg are seven points apart, and at 25% they are more than twenty.
Read the full answer
What the dose should be after goal weight is a separate question that no trial has tested, covered on the maintenance page.

Tirzepatide is the one drug in this class where the question “how much do I give up at a lower dose” has a measured answer. SURMOUNT-1 randomised three maintenance doses, so there is a published curve rather than only titration steps. The curve does not reach anywhere near microdose territory: the lowest randomised maintenance dose was 5 mg weekly, roughly double the top of the range people describe as a microdose.

The approved tirzepatide ladder

Tirzepatide for weight management starts at 2.5 mg weekly for four weeks. That step is initiation only. The maintenance doses in the label are 5, 10 and 15 mg weekly, reached in 2.5 mg increments with four weeks at each step.

Sources describing tirzepatide microdosing put it at roughly 0.5 to 2.5 mg weekly, meaning at or below the initiation step. That description comes from clinic and industry writing, not from a trial or a label.

SURMOUNT-1: three doses, three outcomes

SURMOUNT-1 randomised 2,539 participants to tirzepatide 5, 10 or 15 mg weekly, or placebo, for 72 weeks. Mean body-weight loss was 16.0% at 5 mg and 22.5% at 15 mg, against 2.4% on placebo.

At the 5% threshold the doses look similar: 89% of the 5 mg group and 96% of both the 10 mg and 15 mg groups got there, versus 28% on placebo. The separation appears at the top of the response range. Reaching 25% or more body-weight loss happened for 16.5% at 5 mg, 35% at 10 mg and 39.7% at 15 mg, against 0.3% on placebo.

That last row is the most useful thing in the dataset for anyone weighing a lower dose. Getting a modest result is fairly dose-insensitive. Getting a large one is not.

Dose (weekly)	Mean weight loss, week 72	≥ 5% loss	≥ 25% loss
Placebo	2.4%	28%	0.3%
5 mg	16.0%	89%	16.5%
10 mg	not reported here	96%	35%
15 mg	22.5%	96%	39.7%

Where a microdose falls against that curve

Below it, and off the end of the data. The practice-described microdose range tops out at 2.5 mg weekly, which is the label's four-week initiation step and half the lowest dose SURMOUNT-1 randomised anyone to stay on.

So the curve cannot be extended downwards with any confidence. A straight line drawn from 5 mg to 2.5 mg assumes the dose-response is linear in a region nobody measured, and pharmacology rarely obliges. The trial tells you the 5 mg to 15 mg trade-off precisely and tells you nothing at all below 5 mg.

What is actually known SURMOUNT-1 measured 5, 10 and 15 mg over 72 weeks. Nothing below 5 mg was ever randomised as a maintenance dose, in that trial or any other.

Why the dual mechanism does not settle the question

Tirzepatide activates both the GIP and the GLP-1 receptor, and a common argument runs that a dual agonist should therefore do more per milligram than a single agonist, making low doses more plausible.

The published data do not support that inference. SURMOUNT-1's own curve shows response still climbing from 5 mg to 15 mg, which is the opposite of a mechanism that saturates early. Whatever the receptor pharmacology suggests, the measured outcome in humans kept improving as the dose went up.

What the 5% threshold hides

Anyone arguing that low doses are nearly as good usually reaches for the 5% row, and it is the least informative number in the trial.

At that threshold 89% of the 5 mg group got there and 96% of the 15 mg group did, a gap of seven points. Read alone, that looks like dose barely matters. The 25% threshold in the same trial, in the same participants, over the same 72 weeks, separates 16.5% from 39.7%. Same drug, same comparison, wildly different picture.

The reason is that a low bar gets cleared by almost everyone who responds at all, so it measures whether the drug works rather than how well. If the goal is a few percent of body weight, dose matters less. If the goal is the kind of result people saw in the coverage of these trials, dose is most of it.

Tolerability is the real reason people stay low

Gastrointestinal adverse events drove dose reductions and discontinuations throughout the SURMOUNT programme, and that is why the label titrates at all. For someone who cannot get past 2.5 mg without vomiting, staying low is not a strategy, it is what is left.

That is a clinical conversation with a prescriber, who can slow the titration, treat the nausea, or change agent. The label's four-week steps are a default, not a law of nature. A prescriber holding someone at an initiation dose for longer than four weeks is working inside the label with monitoring attached, which is a different situation from someone deciding on a permanent microdose alone.

The distinction matters for what happens next. A supervised slow titration has a target and a review date. A self-directed microdose usually has neither, and nobody is watching for the symptoms that need reporting.

What is still unknown

No trial has tested tirzepatide below 5 mg as a maintenance dose. No trial has tested whether a low dose preserves weight after someone reaches goal. Cardiovascular and kidney outcome data for this class were generated at label doses, and carrying them to a microdose is not supported.

The safety warnings do not scale down either. Tirzepatide carries a boxed warning for thyroid C-cell tumours and a contraindication for personal or family history of medullary thyroid carcinoma or MEN 2, neither of which is a dose band. Pancreatitis, gallbladder disease and acute kidney injury are label risks at any dose.

The legal supply picture also changed. Broad US compounding of tirzepatide wound down after FDA resolved the shortage in December 2024, with the 503A cut-off on 18 February 2025 and 503B on 19 March 2025. Anyone whose low-dose plan depended on a compounded source is now looking at a different market with different risks.

Questions worth asking about the dose

The SURMOUNT numbers are useful in an appointment, because they turn a vague worry into a specific one.

Given what I am trying to achieve, does the 5 mg versus 15 mg difference matter for me?
Can we hold at a lower step for longer rather than stopping the climb altogether?
If gastrointestinal symptoms are the blocker, what can we treat before reducing the dose?
How would we tell in three months whether the dose I am on is doing anything?
Do any of my other conditions or medicines change what dose is sensible?

The evidence, one row per claim

Claim	Tier	Source
SURMOUNT-1 randomised 2,539 participants to tirzepatide 5, 10, 15 mg or placebo for 72 weeks.	established	NEJM, SURMOUNT-1
Mean weight loss at 72 weeks was 16.0% (5 mg) and 22.5% (15 mg) vs 2.4% placebo; Lilly's published range across doses was 16.0-22.5%.	established	Eli Lilly / NEJM
89% of the 5 mg group and 96% of the 10 and 15 mg groups achieved >=5% weight loss, vs 28% on placebo.	established	Eli Lilly / NEJM
16.5% (5 mg), 35% (10 mg) and 39.7% (15 mg) reached >=25% weight loss vs 0.3% on placebo, i.e. the high-response tail is strongly dose-dependent.	established	Eli Lilly / NEJM
Label maintenance doses for tirzepatide in weight management are 5, 10 and 15 mg weekly after a 2.5 mg initiation step.	established	SURMOUNT-1 / Zepbound label
Legal US compounding of tirzepatide wound down after FDA resolved the shortage on 19 December 2024 (503A cut-off 18 Feb 2025, 503B 19 Mar 2025).	established	FDA, 'FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize' (Internet Archive snapshot)

Sources

Where this comes from

Researched and edited by Thomas Prommer — biohacker, performance athlete, data enthusiast and health coach.

Every number on this page traces to a named source. There are 6 sourced claims below the fold, each with the document it came from.

Sources consulted: NEJM, Eli Lilly / NEJM, SURMOUNT-1 / Zepbound label, FDA.

Not clinically reviewed. This page was researched and written against primary regulatory and trial sources, and no clinician has checked it.

Sources last read 2026-08-23.

Keep reading

Educational content, reviewed 2026-08-23. Not medical advice, not a prescription, and not a substitute for a clinician who knows your history. Doses named here are label schedules or doses used in named trials, never a recommendation to you.

Tirzepatide Microdosing: What SURMOUNT-1 Says About Low Doses