Ozempic (semaglutide) is a glucagon-like peptide-1 (GLP-1) receptor agonist widely prescribed in the UK for type 2 diabetes mellitus. Understanding the relationship between Ozempic and kidney function is crucial, particularly as many people with diabetes have concurrent renal impairment. Whilst semaglutide is not primarily eliminated by the kidneys and does not directly damage renal tissue, certain side effects—especially gastrointestinal symptoms—can lead to dehydration and acute kidney injury if fluid intake is inadequate. Clinical evidence suggests potential renal benefits, including reduced albuminuria, though vigilant monitoring remains essential for safe prescribing.

How Ozempic Affects Kidney Function

Ozempic (semaglutide) is a glucagon-like peptide-1 (GLP-1) receptor agonist licensed in the UK for the treatment of type 2 diabetes mellitus. Understanding its relationship with kidney function is essential for both patients and healthcare professionals, particularly as many individuals with diabetes have concurrent renal impairment.

Semaglutide works by mimicking the action of the naturally occurring hormone GLP-1, which stimulates insulin secretion in a glucose-dependent manner, suppresses glucagon release, and slows gastric emptying. Importantly, semaglutide is not primarily eliminated by the kidneys. The drug undergoes proteolytic degradation similar to endogenous proteins, with renal excretion accounting for only a small fraction of its clearance. This pharmacokinetic profile means that dose adjustments are generally not required in patients with renal impairment, although clinical experience in end-stage renal disease (ESRD) and dialysis is limited, so caution and monitoring are advised in these populations.

Clinical trial data, including the SUSTAIN programme, suggest that Ozempic may offer potential renal benefits in people with type 2 diabetes. Studies have shown a reduction in new-onset and persistent macroalbuminuria, with improvements in urinary albumin-to-creatinine ratio (uACR). These effects are likely related to improved glycaemic control and modest weight reduction, though it's important to note that kidney protection is not a licensed indication for Ozempic in the UK.

Whilst Ozempic does not directly impair kidney function, certain side effects—particularly gastrointestinal symptoms such as nausea, vomiting, and diarrhoea—can lead to dehydration and acute kidney injury (AKI) if fluid intake is inadequate. The Summary of Product Characteristics (SmPC) specifically warns about monitoring renal function when patients experience severe gastrointestinal adverse reactions. This risk is particularly relevant during treatment initiation or dose escalation. Therefore, understanding both the potential benefits and indirect risks is crucial for safe prescribing and patient counselling.

Monitoring Kidney Function During Ozempic Treatment

Routine monitoring of kidney function is an integral component of diabetes care and becomes particularly important when initiating or continuing treatment with Ozempic. NICE guidelines recommend regular assessment of renal function in all patients with type 2 diabetes, regardless of the medications prescribed.

Before starting Ozempic, healthcare professionals should obtain baseline renal function tests, including serum creatinine and estimated glomerular filtration rate (eGFR). These measurements establish a reference point for future comparisons and help identify patients with pre-existing chronic kidney disease (CKD). According to NICE guidance (NG28), patients with diabetes should have their renal function checked at least annually, though more frequent monitoring may be warranted in those with established CKD or other risk factors.

During the initial weeks of treatment, particularly when titrating the dose upwards, patients should be counselled about maintaining adequate hydration, especially if experiencing gastrointestinal side effects. For individuals with moderate to severe renal impairment (eGFR <45 mL/min/1.73m²), clinicians might consider checking renal function 2–4 weeks after starting treatment and following each dose increase, particularly in high-risk patients, though this is not mandated by the SmPC.

Urinary albumin monitoring is also valuable, as reductions in albuminuria may indicate beneficial effects. NICE recommends annual uACR testing in people with diabetes. If significant changes in kidney function occur—either improvement or deterioration—the frequency of monitoring should be adjusted accordingly.

Patients taking concomitant medications that affect renal function, such as ACE inhibitors, ARBs, diuretics, or NSAIDs, require particularly vigilant oversight, as the combination may increase the risk of acute kidney injury during episodes of dehydration. In line with UK 'sick day rules', patients should be advised to consider temporarily withholding Ozempic during acute illness with poor oral intake or dehydration, and to seek clinical advice before restarting.

Referral to specialist nephrology services should be considered according to NICE guidance (NG203) for patients with rapid decline in eGFR, eGFR <30 mL/min/1.73m², ACR ≥70 mg/mmol, or persistent haematuria with albuminuria.

Potential Kidney-Related Side Effects

Whilst Ozempic itself does not directly damage the kidneys, several indirect mechanisms can affect renal function, primarily through volume depletion. The most commonly reported adverse effects of semaglutide are gastrointestinal in nature, occurring in approximately 10-40% of patients according to the SmPC. These include:

• Nausea and vomiting (particularly during dose escalation)

• Diarrhoea

• Reduced appetite and fluid intake

When these symptoms are severe or prolonged, they can lead to dehydration, which reduces renal perfusion and may precipitate acute kidney injury (AKI). This risk is heightened in vulnerable populations, including older adults, those with pre-existing CKD, and patients taking medications that affect fluid balance or renal haemodynamics.

Post-marketing surveillance data and case reports have documented instances of acute kidney injury associated with Ozempic use, though causality is often difficult to establish definitively. In most reported cases, AKI occurred in the context of severe gastrointestinal symptoms with inadequate fluid replacement. The SmPC specifically advises monitoring renal function when patients experience severe gastrointestinal adverse reactions.

There is no established evidence that Ozempic causes chronic kidney disease or directly damages renal tissue. Conversely, clinical trial data suggest potential benefits on albuminuria, with slower progression of some markers of diabetic nephropathy compared to some other glucose-lowering agents. However, individual patient responses vary, and any unexplained decline in renal function warrants thorough investigation.

Rare adverse effects that may indirectly affect the kidneys include pancreatitis (which can cause systemic inflammation and prerenal AKI) and allergic reactions. Patients should be counselled to recognise symptoms of these serious complications and seek immediate medical attention if they occur. Healthcare professionals should maintain a low threshold for temporarily withholding Ozempic during acute illnesses that increase dehydration risk, such as gastroenteritis or febrile infections.

Healthcare professionals and patients are encouraged to report suspected adverse reactions to Ozempic via the MHRA Yellow Card Scheme.

When to Seek Medical Advice About Kidney Health

Patient education is paramount in preventing kidney-related complications during Ozempic treatment. Individuals should be advised to contact their GP or diabetes specialist nurse promptly if they experience:

• Persistent vomiting or diarrhoea lasting more than 24 hours

• Inability to maintain adequate fluid intake

• Signs of dehydration: dizziness, reduced urine output, dark-coloured urine, dry mouth, or excessive thirst

• Unexplained fatigue or weakness

• Swelling of the ankles, feet, or face (which may indicate fluid retention or worsening kidney function)

Patients with pre-existing kidney disease should be particularly vigilant and may benefit from more frequent contact with their healthcare team during treatment initiation. Any acute illness that affects fluid balance—such as gastroenteritis, influenza, or urinary tract infections—warrants medical review, as temporary cessation of Ozempic may be necessary to prevent AKI. In line with UK sick day rules, patients should consider temporarily withholding Ozempic during periods of acute illness with poor oral intake or dehydration, and seek clinical advice before restarting.

Immediate medical attention (via NHS 111 or emergency services) is required if patients develop:

• Severe, persistent abdominal pain (possible pancreatitis)

• Marked reduction in urine output or complete cessation

• Confusion or altered consciousness

• Severe allergic reactions (rash, difficulty breathing, facial swelling)

Healthcare professionals should establish clear safety-netting arrangements, ensuring patients understand when and how to seek help. Regular medication reviews provide opportunities to assess kidney function trends, review concurrent medications that may interact, and reinforce hydration advice. According to NICE guidance (NG203), any patient with diabetes experiencing an acute deterioration in renal function should have a comprehensive assessment, including review of all medications, hydration status, and potential nephrotoxic exposures. Collaborative care between GPs, diabetes specialists, and renal physicians optimises outcomes for patients with complex needs, ensuring that the benefits of Ozempic therapy are realised whilst minimising potential risks to kidney health.

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