Almost every seller on this site charges more for tirzepatide than for semaglutide, and across the sellers publishing both figures the step is a median of $64 a month. That is a large recurring cost to carry on a difference most buyers have only seen described in marketing — see what sellers actually charge. Here is what the trials measured.
The two pivotal obesity trials
STEP 1 randomized 1,961 adults with overweight or obesity and without diabetes to once-weekly semaglutide 2.4 mg or placebo for 68 weeks. Mean weight change from baseline was −14.9% against −2.4% on placebo.[1]
SURMOUNT-1 randomized 2,539 similar adults to tirzepatide or placebo for 72 weeks. Mean reduction was −15.0% at 5 mg, −19.5% at 10 mg and −20.9% at 15 mg, against −3.1% on placebo.[2]
Those are separate trials with different participants and different durations. The tirzepatide figures are larger, and the comparison is not a controlled one. SURMOUNT-5 now answers the direct obesity comparison with both drugs in the same randomized trial.
SURMOUNT-5 directly compared obesity treatment
SURMOUNT-5 randomized 751 adults with obesity and without diabetes to maximum tolerated tirzepatide 10 or 15 mg or semaglutide 1.7 or 2.4 mg for 72 weeks. Mean weight reduction was 20.2% with tirzepatide(95% CI, 19.1–21.4) versus 13.7% with semaglutide(95% CI, 12.6–14.9), a 6.5 percentage point difference. This was an open-label trial funded by Eli Lilly; gastrointestinal adverse events were common with both treatments, mostly during escalation.[5]The SURMOUNT-5 explanationcovers the endpoints and limitations.
SURPASS-2 answers a different diabetes question
SURPASS-2 randomized 1,879 adults with type 2 diabetes to tirzepatide or semaglutide 1 mg — note the dose, lower than the 2.4 mg used for weight — over 40 weeks. Tirzepatide was superior on HbA1c at every dose, and produced greater weight reduction.[3]
That result is frequently cited as proof that tirzepatide beats semaglutide for weight loss. It is not that. It compared a lower semaglutide dose, in a different population, with glycemic control as the primary endpoint. It is real evidence about something adjacent to the question most readers are asking. It also says nothing about the compounded versions most sellers actually supply.
What the price difference is buying
On the trial averages, tirzepatide at its higher doses produced larger mean weight reduction than semaglutide at its labeled obesity dose. What no trial tells you is which will work better for you. Averages conceal wide individual variation, and tolerability decides more real outcomes than potency does — a drug stopped at week six may not deliver the longer-term benefit measured in a trial, which is why the side-effect profile matters as much as the effect size.
The commercial question is separate and worth asking plainly. If a seller charges $99 for semaglutide and $299 for tirzepatide, that is $2,400 a year for a difference the evidence describes as an average across populations. Some sellers charge the same for either, which removes the question entirely — see the tirzepatide board for who does.
Beyond weight
SELECT randomized 17,604 adults with cardiovascular disease and overweight or obesity, without diabetes, to semaglutide 2.4 mg or placebo. The primary cardiovascular endpoint occurred in 6.5% on semaglutide against 8.0% on placebo over a mean 39.8 months — a 20% relative reduction.[4] No equivalent outcome trial has reported for tirzepatide in this population.
That is the clearest asymmetry in the evidence, and it points the other way from the weight figures. If cardiovascular risk is the reason for treatment, semaglutide is the molecule with the outcome data.
What none of this covers
Every trial above studied the branded, FDA-approved products at labeled doses. Most sellers on this site supply compounded versions, which are prepared against a prescription and are not FDA-approved or reviewed for safety, efficacy or quality before dispensing. The trial results describe the molecule, not the vial you receive.