Ozempic®, dehydration and the kidney warning

What the warning describes

Section 5.6 is titled Acute Kidney Injury Due to Volume Depletion; volume depletion means the body has lost too much fluid. The label describes acute kidney injury reported after approval in people using semaglutide, some of whom needed hemodialysis, and notes that most of the reported events happened in people with stomach and bowel reactions that led to dehydration ^[1]. Section 6.2 repeats acute kidney injury in its list of reports received after approval, and section 6 counts it among the serious adverse reactions ^[1].

Europe frames the same risk as a precaution: nausea, vomiting and diarrhoea may cause dehydration, which in rare cases can worsen kidney function, so this should be considered in people with impaired kidneys and patients should take precautions to avoid fluid depletion ^[2]. Canada adds that some reported cases were in people without known kidney disease, lists dehydration, renal impairment and renal failure among post-market reports, and asks for caution when starting or raising Ozempic® in people with kidney impairment ^[3].

The stomach reactions behind it

The warning points to three reactions in particular. All three were more frequent on Ozempic® than on placebo in the two US placebo-controlled studies of adults with type 2 diabetes, and the label says most reports of them came during dose escalation ^[1].

What kidney data from trials show

A post hoc analysis of the SUSTAIN 1 to 7 trials, covering 8,416 adults with type 2 diabetes, found that estimated kidney function (eGFR) fell slightly in the first 12 weeks with all active treatments and then levelled off. By the end of treatment, eGFR on semaglutide did not differ from placebo overall, protein in the urine fell, and kidney adverse events were balanced between groups. The analysis was funded by the manufacturer ^[4].

Canada pools four large trials of semaglutide in people with type 2 diabetes and heart or kidney disease, including FLOW. Serious acute kidney injury was reported in 2.9% on semaglutide and 3.3% on placebo. In people with chronic kidney disease, serious and severe adverse events were more frequent than in people with heart disease alone, on both semaglutide and placebo ^[3].

A 2025 analysis of the US FDA adverse event reporting system looked at reports involving semaglutide in type 2 diabetes and found no signal of acute or chronic kidney injury. Reporting data cannot show how often a problem occurs, only whether it is reported more often than expected ^[6].

Existing kidney disease and the FLOW indication

In the trials behind the US safety table, about 36% of participants had mildly reduced kidney function at the start and about 7% moderately reduced, and section 8.6 says no dose change is recommended for kidney impairment ^[1].

Ozempic® also has an approval, based on the FLOW trial of 3,533 adults with type 2 diabetes and chronic kidney disease, to lower the risk of sustained eGFR decline, end-stage kidney disease and cardiovascular death. In FLOW the main kidney and heart outcome was 24% less frequent on Ozempic® 1 mg than on placebo, and the label notes that no new serious or severe adverse reactions were identified ^[1][5]. Our separate article on Ozempic® and chronic kidney disease covers that indication.

Why it may happen

What the label supports: the chain runs from stomach reactions to fluid loss to kidney injury. The label says most reported cases followed dehydration from nausea, vomiting or diarrhea ^[1].

What is not established: the documents do not describe a direct toxic effect of semaglutide on the kidney, and the US label says the mechanism behind the kidney benefit in FLOW has not been established either ^[1].

General background: MedlinePlus lists dehydration and very low blood pressure among causes of reduced blood flow to the kidneys that can lead to acute kidney failure ^[7].

Other causes of acute kidney injury

• Dehydration from any cause, including fever, heat, vomiting or diarrhoea from a stomach bug, or not drinking enough when unwell ^[7][8].
• Medicines including non-steroidal anti-inflammatory drugs (NSAIDs), certain antibiotics and blood pressure medicines, and contrast dye used in scans ^[7].
• Blockage of the urinary tract, severe infections and conditions affecting blood flow to the kidneys ^[7].
• Diuretics and uncontrolled diabetes, which can make you pass more urine and lose fluid ^[8].

What may help

• Drink fluids to lower the chance of dehydration, as the Medication Guide advises, and take precautions against fluid loss, as Europe and section 17 put it ^[1][2].
• Report nausea, vomiting or diarrhea that will not stop to your healthcare provider promptly ^[1].
• MedlinePlus advises drinking plenty of fluids when you have a fever, vomiting or diarrhoea, and calling a provider before dehydration sets in if you think it may happen ^[8].
• If you use NSAIDs, diuretics or blood pressure medicines, ask your prescriber or pharmacist what to do on days when you cannot keep fluids down; do not stop or change a medicine on your own ^[7].

Keeping fluids and symptoms on record

When stomach symptoms hit, note how many times you vomited or had diarrhea, roughly how much you drank, when you last passed urine and its colour, and any dizziness. Several days of symptoms and fluid notes side by side make it easier to tell your provider how long things have been going on.

Ozempic® is a registered trademark of Novo Nordisk A/S. PepLabo is not affiliated with or endorsed by Novo Nordisk.