Usually not. Among 3,660 patients with at least one baseline non-GLP-1 glucose-lowering drug, the recorded count went down for 17.2% and up for 44.0% [1]. The median count rose from one substance to two. For most people the list got longer.
One reasonable hope when starting an expensive new drug is that it replaces something you are already paying for. This study tracked what actually happened to the rest of the regimen. The version of that question involving insulin specifically is in what swapping mealtime insulin actually buys. That is the one case where a substitution is the point.
The spread between molecules
The spread between drugs is the most interesting number and the least explained. Higher counts followed dulaglutide in 52.9% of patients and tirzepatide in 20.4% — a difference of more than two and a half times. Potency is the obvious candidate, since a more effective drug should require less help. Era is another: dulaglutide users started earlier, when prescribing habits and available alternatives were different. Nothing in the abstract separates the two.
The one substitution with trials behind it
Mealtime insulin is the exception. Across seven randomized trials, replacing it with a GLP-1-based strategy left HbA1c unchanged at −0.08 points [2]. It cut total daily insulin by 33.32 units and took off 4.94 kg.
A null on HbA1c is the objective there rather than a failure. What it buys is fewer injections and less weight, at many times the price of the insulin removed. So the trade in money runs opposite to the trade in convenience. Nothing on this page is a reason to change an insulin regimen without a prescriber directing it.
What a longer list costs in practice
Each added medication is another chance for the chain to break. In a pragmatic trial, participants filled prescriptions through their own insurance [3]. 84% assigned one drug had filled it at four months, against 53% assigned two. Among those who did fill, 49% of the dual group later discontinued one.
Those were insured patients, in a trial, with staff helping, so the friction measured there is the floor rather than the ceiling. A self-pay buyer meets the same pharmacy and the same side effects without either.
What does get replaced is a target, not a tablet
The package people think they are buying is weight, blood pressure and cholesterol at once. A post hoc analysis of the SURMOUNT trials counted how often all three arrived together [4]. At the 5% weight threshold, 32–38% of tirzepatide participants hit all three against 2–8% on placebo.
Read the other way, most participants did not hit all three, and some who missed a target improved on it anyway. A blood pressure drug coming off is a clinical decision made on a reading, not something a weight-loss result guarantees.
What this means for a budget
For a reader budgeting, the practical reading is that adding one of these drugs is more likely to add cost than to move it. Fewer than one in five patients ended up on fewer medications, and the modal outcome was more. That belongs alongside the price picture in what a GLP-1 actually costs and the gap between advertised and billed amounts in the headline against the bill.
The setting is the same Polish private network behind the PCOS prescribing trends. Two findings from one data source are not two independent observations, and neither describes a US cash market.