Study suggests dosing may be more important than drug brand in weight loss for type 2 diabetes

New research indicates that matching doses of semaglutide and tirzepatide yields comparable weight loss in type 2 diabetes, highlighting the potential for dose-based substitution amid supply and cost pressures.

A new attempt to answer one of obesity and diabetes medicine’s most practical questions suggests the key issue may be dose, not brand. A paper in Diabetes Therapy, listed by PubMed as published in July 2026, found that semaglutide 2.4mg weekly and tirzepatide 10mg weekly had a very high probability of producing equivalent weight loss in people with type 2 diabetes, with a second high-probability match at semaglutide 7.2mg and tirzepatide 15mg. The finding lands as drug switches have become more common because of cost, supply and insurance pressures.

The study was led by Carlos E. Builes-Montaño with Andrés F. Suárez-Rodríguez and Maria A. Alzate-Vinasco. Using 48 treatment arms from 23 phase III randomised trials involving 16,524 participants, the researchers pulled together evidence from the SUSTAIN, STEP, SURPASS and SURMOUNT programmes. Fifteen trials informed the semaglutide analysis, covering weekly doses from 0.5mg to 7.2mg, while eight informed the tirzepatide side at 5mg, 10mg and 15mg. Across the trial programmes, participants were broadly similar, with a mean age of about 55, baseline HbA1c close to 7.8% and body mass index around 33 to 34.

Rather than rely on a single direct comparison, the authors built dose-response curves for both medicines. They used generalised additive models to trace how weight loss changed as dose increased, then a Bayesian hierarchical model to estimate how likely prespecified dose pairs were to sit within an equivalence margin of two percentage points of body-weight change. Treatment duration, which ranged from 26 to 104 weeks, was built into the analysis, and study-level differences were handled statistically. Crucially, though, this was done with trial-arm averages rather than records for individual patients.

What emerged was a similar shape for both drugs: the earliest dose increases brought the biggest gains, while extra benefit tapered as doses rose. For semaglutide, the model put median weight loss at roughly 5% to 6% at 1mg a week and about 10% at 2.4mg, with further reduction at 7.2mg. Tirzepatide showed a steady gradient across 5mg to 15mg. The strongest dose matches were semaglutide 2.4mg versus tirzepatide 10mg, with a 99.4% posterior probability of equivalence, and semaglutide 7.2mg versus tirzepatide 15mg, at 94.8%. Lower-dose semaglutide did not look comparable to the higher tirzepatide regimens.

The paper also tried to turn those curves into bedside decisions. For someone already taking semaglutide 1mg, either stepping up to 2.4mg or changing to tirzepatide 5mg was likely to improve weight loss, but remaining on semaglutide and titrating upwards had the better chance of adding at least two more percentage points of weight reduction. At the other end of the range, the model suggested that some patients on tirzepatide 10mg might gain more from moving to semaglutide 7.2mg than from increasing tirzepatide to 15mg. The authors presented that as a modelling insight, not a blanket recommendation, but it reinforces the idea that dose equivalence may matter more than the badge on the pen.

That message overlaps with a separate line of evidence Novo Nordisk pushed earlier this year through an official release and market reports carried by Reuters, Yahoo Finance and other investor outlets. On 6 June, the company said a retrospective US claims analysis involving more than 64,000 adults with type 2 diabetes showed that patients moved from semaglutide 1mg to 2mg were about as likely as those switched to tirzepatide to reach HbA1c below 7% after one year. In a weight-loss cohort of more than 56,000 adults, 60.5% of those escalated to semaglutide 2mg achieved at least 5% weight loss, compared with 55.3% of those switched to tirzepatide. Michael Radin, an executive medical director at Novo Nordisk, said the findings addressed “an important clinical consideration” because “dose escalation of current therapy may get patients to their treatment goals”.

There are, however, reasons not to read too much into either analysis. The Diabetes Therapy paper did not formally model adverse events or discontinuation, treated the semaglutide 7.2mg estimate as exploratory because it came from a single trial, and examined weight loss rather than broader outcomes such as cardiovascular events or overall safety. The company’s real-world claims study carried a different set of caveats. Novo Nordisk said itself that retrospective claims data can show associations but cannot prove causation, and that such databases may miss people with intermittent cover or underserved populations.

Taken together, the evidence points to a more complicated picture than a straight semaglutide-versus-tirzepatide contest. In type 2 diabetes, lower semaglutide doses do not appear to match higher tirzepatide doses for weight loss, but some higher-dose pairings may be close enough to guide a planned switch when shortages, formularies, side effects or cost force a change. For prescribers, that offers a more quantitative way to think about substitutions. For patients, it is a reminder that the number of milligrams may matter at least as much as the molecule itself.