Semaglutide and Kidney Disease: FLOW Results

Semaglutide reduced a combined kidney-and-cardiovascular outcome in FLOW, a randomized trial of adults with type 2 diabetes and chronic kidney disease. The often-quoted 24% reduction is a relative reduction in the hazard of that combined outcome. It is not a 24-percentage-point reduction in dialysis, and it does not establish kidney protection for everyone taking semaglutide for weight loss. ¹

Who was actually studied?

FLOW randomized 3,533 adults to weekly subcutaneous semaglutide 1.0 mg or placebo. Participants had type 2 diabetes and chronic kidney disease defined by kidney filtration and urine albumin criteria. This was a population already at substantial risk, rather than a general weight-management sample. Median follow-up was 3.4 years; the trial stopped early after a prespecified interim analysis. ¹

The entry criteria matter. People with an estimated glomerular filtration rate, or eGFR, of 50–75 mL/min/1.73 m² needed a urine albumin-to-creatinine ratio above 300 and below 5,000 mg/g. Those with eGFR of 25 to below 50 mL/min/1.73 m² needed a ratio above 100 and below 5,000 mg/g. These are trial eligibility details, not instructions to diagnose yourself or decide on treatment from one laboratory result. ¹

A trial can be persuasive within its population while leaving other questions unanswered. FLOW does not directly establish the same effect in people without diabetes, in people with normal kidney function, or in every cause and stage of kidney disease. Nor does it test a telehealth company's particular compounded preparation. The tested medicine, route and population belong with any statement of the result.

What the 24% figure measures

The primary outcome combined kidney failure, a sustained major decline in filtration, and death from kidney or cardiovascular causes. There were 331 first primary-outcome events among 1,767 people assigned semaglutide and 410 among 1,766 assigned placebo. The hazard ratio was 0.76, with a 95% confidence interval of 0.66–0.88. ¹

Subtracting 0.76 from 1 gives the reported 24% relative hazard reduction. It describes the comparison over follow-up, accounting for the timing of events. It is different from subtracting the proportions of people who experienced an event. Using the published counts gives approximately 18.7% versus 23.2%, a crude difference of about 4.5 percentage points over the observed follow-up. That calculation helps with scale but does not replace the trial's time-to-event analysis. ¹

This distinction is especially important when a headline replaces the outcome with “dialysis.” FLOW's combined result cannot be described as a 24% reduction in dialysis alone. Likewise, including cardiovascular death does not make the trial irrelevant to kidney care; it means the result answers a broader question than filtration alone. Readers should be able to see that broader question before being asked to interpret the percentage.

What changed in the approved indication?

The January 2025 Ozempic label includes reducing sustained eGFR decline, end-stage kidney disease and cardiovascular death in adults with type 2 diabetes and chronic kidney disease. That is a product-specific indication with a defined patient group. It should not be rewritten as approval to prevent kidney disease in any person who wants to lose weight. ²

Does every semaglutide product have the same evidence?

The same ingredient can appear in different products with different evidence and labeling. A prescription should identify the actual finished medicine and treatment purpose. The semaglutide cardiovascular evidence provides another example: a result becomes more useful when the population and outcome stay attached to it.

For a product-level comparison, the NovoCare Pharmacy review lists named Ozempic and Wegovy presentations separately. Confirm the finished product and intended indication with your clinician before applying a kidney-outcomes claim to an offer described simply as semaglutide.

Approval also does not mean semaglutide replaces every other part of kidney care. FLOW compared an additional treatment strategy with placebo under the trial's care arrangements. It was not a test of abandoning existing medicines or monitoring. Decisions about combinations belong with the clinicians who know the patient's blood pressure, glucose control, kidney measurements and other treatments.

Kidney benefit does not remove the need to watch dehydration

A long-term benefit and a short-term adverse effect can both be real. Ozempic's label warns about acute kidney injury due to volume depletion and recommends monitoring kidney function when adverse reactions could cause dehydration. Nausea, vomiting and diarrhea are among the common adverse reactions. A person who is struggling to keep fluids down should contact the care team rather than interpret the kidney indication as protection from all kidney problems. ²

This is a practical reason to agree on follow-up before starting treatment. Ask whom to contact for persistent gastrointestinal symptoms, how the clinical team coordinates with existing kidney care, and which laboratory results it will review. These questions are more useful than asking whether the medicine is simply “good” or “bad” for kidneys.

The study's average benefit cannot determine an individual's balance of risks. A clinician also needs to consider contraindications, other medicines and the reason for treatment. This article explains the evidence; it does not provide a starting dose, a titration plan or instructions to replace a current prescription.

What remains uncertain?

Early stopping was prespecified, which is different from stopping after an informal look at favorable numbers. Nevertheless, the published follow-up is the follow-up available; it is not lifetime observation. The study was funded by Novo Nordisk, and replication and longer-term evidence remain valuable even when a randomized result is convincing. ¹

The most useful unanswered questions concern applicability. How closely does a particular patient resemble the enrolled group? Which other treatments are already being used? Is the proposed medicine the approved product studied? These are narrower, answerable questions than whether all GLP-1 products protect all kidneys.

For someone with type 2 diabetes and CKD, FLOW supplies meaningful evidence to discuss with the care team. For someone without those conditions, it is a reason to understand the limits of a headline rather than assume the same measured benefit. Keep the diagnosis, formulation and outcome together when comparing claims.