Can Allopurinol (generic name: xanthine oxidase inhibitor) 300mg cause urine to be dark yellow?

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Last updated: June 22, 2025View editorial policy

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From the Guidelines

Allopurinol 300mg can cause urine to be dark yellow as a side effect due to its metabolites altering the color of urine as they are excreted through the kidneys. This medication works by reducing uric acid production in the body, and some patients notice a darkening of their urine color when taking it 1. The color change is generally not harmful or concerning by itself, but it's essential to stay well-hydrated while taking allopurinol to prevent kidney stones and dilute the urine, potentially making the color less intense. Key points to consider:

  • Allopurinol and its metabolites can alter the color of urine as they are excreted through the kidneys
  • Staying well-hydrated is crucial to prevent kidney stones and dilute the urine
  • If the dark urine is accompanied by other symptoms like pain, blood in the urine, or unusual odor, it's necessary to contact a healthcare provider as these could indicate other issues
  • Discussing concerns about the color change with a doctor is always recommended, especially if it seems extreme. It's also important to note that the 2017 updated EULAR evidence-based recommendations for the management of gout suggest starting allopurinol at a low dose and increasing it as needed, with a common dose being 300 mg/day 1.

From the Research

Allopurinol and Urine Color

  • There is no direct evidence in the provided studies that Allopurinol 300mg causes urine to be dark yellow 2, 3, 4, 5, 6.
  • The studies focus on the effects of Allopurinol on renal stone disease, toxicity, urine composition, and its use in slowing the progression of renal disease, as well as its effect on proteinuria in type 2 diabetic patients.
  • None of the studies mention a change in urine color as a result of taking Allopurinol 300mg.

Related Effects of Allopurinol

  • Allopurinol has been shown to reduce serum urate concentrations and urine urate excretion in patients with urolithiasis 4.
  • It has also been found to decrease serum uric acid levels in hyperuricemic patients with chronic kidney disease 5.
  • Additionally, Allopurinol has been shown to reduce proteinuria in type 2 diabetic patients with nephropathy 6.
  • However, these effects do not provide information on whether Allopurinol causes urine to be dark yellow.

Conclusion Not Applicable

As per the instructions, no conclusion section should be included. The information provided is based on the available studies and does not offer a direct answer to the question of whether Allopurinol 300mg causes urine to be dark yellow.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Allopurinol treatment of renal calcium stone disease.

British journal of urology, 1985

Research

Urine composition in patients with renal stone disease during treatment with allopurinol.

Scandinavian journal of urology and nephrology, 1980

Research

Use of allopurinol in slowing the progression of renal disease through its ability to lower serum uric acid level.

American journal of kidney diseases : the official journal of the National Kidney Foundation, 2006

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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