Comparison

Semaglutide vs tirzepatide

One targets a single receptor, the other two. The trial averages differ by about six percentage points of body weight — and the cheaper one to buy is not the more effective one.

Updated 2026-08-145 sources

What is different about them

Semaglutide is a GLP-1 receptor agonist. Tirzepatide is a dual agonist, acting at both the GIP and GLP-1 receptors. Both are once-weekly injections; semaglutide is also available as a tablet.

Semaglutide and tirzepatide compared
	Semaglutide	Tirzepatide
Target	GLP-1 receptor	GIP and GLP-1 receptors
Brands	Wegovy, Ozempic	Zepbound, Mounjaro
Dosing	Once weekly injection, or tablet	Once weekly injection
Headline trial result	−14.9% at 68 weeks (STEP 1, 2.4 mg)	−20.9% at 72 weeks (SURMOUNT-1, 15 mg)
Placebo arm	−2.4%	−3.1%
Cheapest verified brand price	$149/mo (Wegovy pill, NovoCare)	$299/mo (Zepbound 2.5 mg, LillyDirect)
Cheapest verified compounded	$169/mo all-in (Alloy)	$199/mo all-in (Alloy)

What the trial numbers do and do not mean

The two headline figures come from different trials with different populations, durations and designs. They were not run head-to-head, so the six-point gap is a comparison of two separate results rather than a measured difference between the drugs.

Both figures are also averages among people who stayed on treatment for the full trial period, in a supported research setting. A subscription is not that setting.

The cost inversion

The larger average effect is currently the more expensive molecule to buy brand-name: $299/month at Lilly’s starting dose against $149/month for the Wegovy pill through NovoCare. On the compounded side the gap narrows to about $30/month at Alloy.

What compounded means, and where the rules are heading

Compounded GLP-1s are not FDA-approved products. Several of the services selling them say so on their own sales pages: Alloy states that “unlike FDA-approved drugs, compounded medications are not reviewed by the FDA for safety, effectiveness, or quality,” and Noom draws the sharper distinction — its product is “produced in an FDA-registered facility but has not been reviewed by the FDA for safety, efficacy, or quality.” A registered facility is not a reviewed medicine.

This tier is now under active enforcement. FDA announced 30 warning letters to telehealth companies in March 2026 and a further 25 in June, over false or misleading marketing of compounded GLP-1 products — including claiming or implying FDA approval, and describing a compounding pharmacy or outsourcing facility as “FDA-approved” or “FDA-licensed,” which is an authorisation the agency does not grant. Five providers reviewed on this site are named recipients; their reviews say so at the top.

The larger development is structural, and it is worth quoting exactly. In a notice published on 1 May 2026 (91 FR 23431, Docket FDA-2018-N-3240), FDA said it “proposes not to include on the 503B Bulks List: semaglutide, tirzepatide, and liraglutide.” That list is the set of substances for which FDA has found “a clinical need for outsourcing facilities to use in compounding”. Leaving all three off it would remove the legal basis for 503B outsourcing facilities to compound them in bulk — which is most of the cheap tier on this site.

It is a proposal, not a rule, and it is not settled. FDA extended the comment period on 26 June 2026, moving the deadline to 30 July. Nothing has been finalised as of this update. But anyone signing a twelve-month prepaid compounded plan should understand that the supply may not be lawful for the length of the plan, and should ask the provider what happens to the balance if it is not.

We could not retrieve fda.gov directly during this research, so the warning-letter counts are cited from the search index. The Federal Register notices above are quoted from the Federal Register’s own API.

Questions

Which one works better?

Tirzepatide produced the larger average change in its trial — −20.9% at 72 weeks against −14.9% at 68 weeks for semaglutide. But those are separate trials, not a head-to-head comparison, and individual response varies widely.

Which is cheaper?

Semaglutide, at the moment. The Wegovy pill is published at $149/month self-pay through NovoCare, against $299/month for Zepbound’s starting dose through LillyDirect.

Can I switch between them?

That is a clinical decision. Dosing is not interchangeable between the two molecules and switching needs a prescriber’s involvement.

Sources

Everything on this page traces to one of the links below, retrieved on the date shown. Prices and programme terms in this market change without notice — confirm against the provider before you buy.

01NovoCare Pharmacy — Wegovy doses, pricing and shippingretrieved 2026-08-14
02LillyDirect — Zepbound pricing and fulfilmentretrieved 2026-08-14
03Alloy — compounded semaglutide pricing and membershipretrieved 2026-08-14
04Alloy — compounded tirzepatide, shipping and FDA caveatretrieved 2026-08-14
05Sesame — semaglutide pricing, labs and compounded positionretrieved 2026-08-14