How Long Is the Evidence, Actually?

These medicines are prescribed as indefinite treatment. Stop and the weight returns, which is the finding every trial of stopping has produced — so the plan, stated or not, is usually “continue”. It is worth knowing how much of that indefinite future has actually been observed. In the largest and longest randomized trial at the weight indication, the mean time participants spent taking the drug was 34.2 months.^[2] Just under three years.

What the long trials actually ran for

So the honest summary is that the weight-indication evidence runs to roughly two to three years, and the longest randomized exposure of any kind in this class sits under four. For a treatment framed as ongoing, that is the whole of what has been watched.

Why the diabetes trials do not simply fill the gap

GLP-1 medicines have been prescribed in type 2 diabetes far longer than they have for weight, and it is tempting to treat that history as reassurance that covers everything. Partly it does. LEADER randomized people to liraglutide with a median follow-up of 3.8 years, and it is a genuine long-duration safety dataset.^[3]

But it does not transfer cleanly. Those trials studied a different population, at different doses, for a different purpose. Semaglutide at 2.4 mg for weight is a substantially higher dose than the diabetes trials used, and the people taking it are on average healthier and younger. Reassurance from one setting is worth something in the other; it is not the same as having been measured there.

What a short evidence base does and does not mean

This is the part that gets distorted in both directions, so it is worth stating flatly.

• It does not predict harm. No signal has emerged at three years that was invisible at one. Nothing here is a reason to expect something to go wrong at year five.
• It does mean the answer is unknown, to everyone, including your prescriber and including us. Ten-year data on semaglutide at the weight dose does not exist because ten years have not passed.
• The comparison is not against certainty. Living with untreated obesity has its own long-term outcomes, and they are well characterized and not good. A short evidence base on a treatment is not automatically worse than a long evidence base on the alternative.
• The cardiovascular finding is real and came from the long trial. In SELECT, a primary cardiovascular event occurred in 6.5% on semaglutide against 8.0% on placebo.^[2] Long trials are how benefits of that kind get found at all.

The unknown here is genuinely unknown. That is different from hidden, and different from bad.

What this means for a decision you are actually making

The practical consequence is not “do not take it”. It is that the indefinite part of indefinite treatment should be a conversation, held early, with someone who knows your history — rather than something you discover at the point where the supply or the money stops.

Two things follow from that. First, whether you can keep getting it is a clinical question and not only a financial one, because stopping has a predictable result: our what happens when you stop covers the trial evidence, and the price tracker keeps a dated figure for every seller we follow. Second, being on a treatment whose long-term record is still being written is a reason for ordinary monitoring, not alarm.