Dark urine on Ozempic (semaglutide) concerns many patients, though it is not listed as a common side effect in UK regulatory documentation. Most cases result from dehydration caused by the medication's gastrointestinal effects—particularly nausea, vomiting, and diarrhoea—which lead to concentrated urine appearing darker in colour. Whilst often benign and reversible with increased fluid intake, persistent dark urine may occasionally indicate more serious conditions requiring medical evaluation, including gallbladder disease, hepatobiliary disorders, or acute kidney injury. Understanding when dark urine represents a temporary, manageable effect versus a warning sign helps patients use Ozempic safely and seek appropriate medical advice when necessary.

What Causes Dark Urine When Taking Ozempic?

Dark urine whilst taking Ozempic (semaglutide) can arise from several mechanisms, though it is not directly listed as a common adverse effect in the product's Summary of Product Characteristics. Understanding the potential causes requires consideration of both the medication's pharmacological effects and indirect physiological changes.

Dehydration represents the most frequent cause of dark urine in patients taking Ozempic. The medication works as a glucagon-like peptide-1 (GLP-1) receptor agonist, which slows gastric emptying and reduces appetite. Common gastrointestinal side effects—particularly nausea, vomiting, and diarrhoea—can lead to significant fluid loss. When the body becomes dehydrated, the kidneys conserve water by producing more concentrated urine, which appears darker in colour, ranging from deep yellow to amber. This concentration effect increases the density of urobilin and other pigments normally present in urine.

Other potential causes warrant consideration, particularly in the context of weight loss and metabolic changes. Dietary changes often accompany Ozempic therapy—reduced food intake or altered eating patterns may affect hydration status and urinary concentration. Additionally, certain foods and supplements can naturally alter urine colour independently of any medication effects.

Rarely, dark urine may indicate more serious conditions requiring prompt medical evaluation. These include gallbladder disease (cholelithiasis is a recognised side effect of Ozempic), hepatobiliary disorders (where bilirubin enters the urine, creating a tea-coloured appearance), or acute kidney injury (which has been reported with semaglutide, typically in the context of dehydration). Other common causes unrelated to medication include urinary tract infections or blood in the urine (haematuria), which may coincidentally occur during treatment.

Is Dark Urine a Common Side Effect of Ozempic?

Dark urine is not classified as a common or documented side effect of Ozempic in regulatory documentation from the MHRA or EMA. The medication's known adverse effect profile, as detailed in the Summary of Product Characteristics (SmPC), does not specifically list changes in urine colour as a recognised occurrence. However, this does not mean patients never experience this symptom—rather, it reflects that dark urine typically results from secondary effects rather than direct drug action.

The most common side effects of Ozempic affect the gastrointestinal system, as documented in the SmPC. These include:

• Nausea (very common, affecting more than 1 in 10 people)

• Diarrhoea (common, affecting up to 1 in 10 people)

• Vomiting (common)

• Constipation (common)

• Abdominal pain and discomfort (common)

These gastrointestinal effects create the conditions for dehydration, which subsequently causes urine to become concentrated and darker. The frequency of dark urine therefore correlates more closely with the severity and duration of these primary side effects rather than representing an independent adverse reaction to semaglutide itself.

According to the SmPC, gastrointestinal adverse reactions are most frequent during treatment initiation and dose escalation, and tend to diminish over time. Maintaining adequate hydration, particularly during the titration period, can help prevent dehydration-related dark urine. When dark urine does occur in Ozempic users, it most commonly appears during these initial weeks or following dose increases.

It is important to distinguish between dark urine caused by concentration (which appears deep yellow to amber and clears with increased fluid intake) and abnormal pigmentation suggesting pathology (such as tea-coloured urine indicating bilirubin, or red-brown urine suggesting blood or myoglobin). The former is a benign, reversible finding; the latter requires immediate medical assessment.

When to Seek Medical Advice About Dark Urine on Ozempic

Patients should contact their GP or diabetes team promptly if dark urine persists despite adequate hydration or if it accompanies other concerning symptoms. Whilst isolated episodes of concentrated urine due to temporary dehydration rarely require urgent intervention, certain presentations warrant timely medical evaluation to exclude serious underlying conditions.

Seek medical advice within 24-48 hours if you experience:

• Dark urine that does not lighten after increasing your fluid intake (aim for pale yellow urine, but follow any specific fluid restriction advice if you have heart or kidney disease)

• Urine that appears tea-coloured, cola-coloured, or brown (suggesting possible bilirubin)

• Persistent dark urine lasting more than 2-3 days

• Accompanying symptoms such as pale stools or yellowing of the skin or eyes (jaundice)

• Reduced urine output or difficulty passing urine

• Unexplained fatigue, weakness, or confusion

Seek immediate medical attention (contact 999 or attend A&E) if dark urine occurs alongside:

• Severe, persistent abdominal pain, particularly if accompanied by vomiting (possible pancreatitis—stop taking Ozempic pending medical review)

• Persistent vomiting preventing fluid intake

• Signs of severe dehydration (dizziness when standing, rapid heartbeat, very dry mouth, sunken eyes)

• Fever with dark urine

• Heavy bleeding in urine with clots or inability to pass urine

NICE guidance on acute kidney injury (NG148) emphasises the importance of monitoring patients on medications that may affect renal function, particularly when combined with dehydration. Healthcare professionals should assess renal function through blood tests (urea, creatinine, electrolytes) and urinalysis if dark urine persists or if there are risk factors for kidney problems.

Before your appointment, it can be helpful to note the colour and frequency of urination, fluid intake, any other medications or supplements taken, and associated symptoms. This information assists clinicians in determining whether investigations such as liver function tests, urinalysis, or renal function assessment are necessary.

If you suspect your dark urine is a side effect of Ozempic, you can report this through the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk or via the Yellow Card app).

Other Ozempic Side Effects That May Affect Urine Colour

Beyond dehydration-related concentration, several other mechanisms associated with Ozempic therapy may indirectly influence urine appearance, though these are less common. Understanding these potential connections helps patients and healthcare professionals distinguish between benign changes and those requiring investigation.

Gastrointestinal side effects remain the primary pathway through which Ozempic affects urinary characteristics. Severe or prolonged diarrhoea and vomiting can lead to electrolyte imbalances and acute kidney injury, both of which may alter urine concentration and colour. The MHRA/emc SmPC for Ozempic notes that renal impairment has been reported, typically in the context of dehydration from gastrointestinal side effects. Patients experiencing persistent gastrointestinal symptoms should maintain careful attention to hydration status and consider oral rehydration solutions containing electrolytes, not just water alone.

Dietary changes accompanying Ozempic use can also affect urine colour through entirely benign mechanisms. The medication's appetite-suppressing effects often lead to reduced food intake and altered dietary patterns. Certain foods and beverages naturally influence urine colour—for example, beetroot can cause pink or red urine, whilst B vitamins (often in multivitamin supplements) produce bright yellow urine. Patients eating less may also consume different proportions of these foods or may take supplements to compensate for reduced dietary intake.

Ketosis resulting from significant caloric restriction may occur in some patients experiencing substantial weight loss on Ozempic. When the body metabolises fat for energy in the absence of sufficient carbohydrate intake, ketone bodies are produced and excreted in urine. Whilst ketones themselves do not typically darken urine significantly, the associated metabolic state and potential dehydration can contribute to darker urine colour. Patients following very low-carbohydrate diets alongside Ozempic therapy should be particularly mindful of hydration.

Gallbladder disease is a recognised risk with semaglutide and may present with jaundice and dark urine. The SmPC lists cholelithiasis (gallstones) as a common side effect. Other serious but rare adverse effects documented with GLP-1 receptor agonists include acute pancreatitis. Dark urine accompanied by jaundice, severe abdominal pain, or significantly reduced urine output requires immediate medical evaluation to exclude these serious complications. Healthcare professionals should maintain a low threshold for investigating persistent or unexplained changes in urine colour, particularly when accompanied by systemic symptoms.

Note that Ozempic is licensed in the UK for the treatment of type 2 diabetes. While weight loss may occur with Ozempic, the specific semaglutide product licensed for weight management is Wegovy.

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