FLOW (trial)

FLOW was the first large trial built to ask whether a GLP-1 protects kidneys, rather than noticing kidney effects as a side finding. It randomized 3,533 adults who had both type 2 diabetes and chronic kidney disease to semaglutide 1 mg weekly or placebo. Entry required a measurable degree of kidney impairment, defined by eGFR together with the amount of albumin leaking into urine. Perkovic and colleagues published it in the New England Journal of Medicine in 2024.

The primary outcome bundled the things patients and nephrologists actually fear: kidney failure, a sustained 50% fall in eGFR from baseline, or death from kidney or cardiovascular causes. Events occurred in 331 people on semaglutide versus 410 on placebo — a 24% lower risk, hazard ratio 0.76. The trial was stopped early on an interim analysis because the benefit was already clear.

The secondary results were consistent rather than isolated. The kidney-specific components alone improved (hazard ratio 0.79), major cardiovascular events fell 18%, and death from any cause fell 20%. When several different endpoints move together in the same direction, the finding is harder to dismiss as chance.

FLOW rewrote a label. Ozempic now carries an indication to reduce the risk of sustained eGFR decline, end-stage kidney disease and cardiovascular death in adults with type 2 diabetes and chronic kidney disease. The common confusion is extending that to everyone: FLOW studied people who had both diabetes and established kidney disease, and it used the 1 mg diabetes dose, not the 2.4 mg weight-management dose.

Worth asking your clinician: whether your kidney function is being tracked with both eGFR and urine albumin, whether you are also on an SGLT2 inhibitor or an ACE inhibitor (the combinations these trials were layered on top of), and how dehydration from GLP-1 side effects should be handled. Our FLOW deep dive and kidney study roundup go further.