Test Overview

Test Methodology

Compound Enzyme Assay

Test Usage

Renal function test, patients who form calcium oxalate kidney stones appear to absorb and excrete a higher portion of dietary oxalate in urine than do normal patients.

Reference Range*

Less than 40 mg/24 hrs (less than 456 mcMol/24 hrs)

* Reference ranges may change over time. Please refer to the original patient report when evaluating results.

Test Details

Days Test Performed

Weekly, Wednesday.

Analytic Time

8 hours

Soft Order Code


MiChart Code

Oxalate, 24 HR Urine



Calcium Oxalate
Oxalic Acid
Oxalic Acid, Urine

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Chemical Pathology

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Specimen Requirements

Offsite Collection Instructions

Collect 24 hour urine specimen. Add 25 mL of 50% glacial acetic acid (15 mL for pediatric patients) to container prior to start of collection. Following collection, mix very well to dissolve any oxalate crystals that may have formed, measure 24 hour urine volume, aliquot 10 mL into a plastic urine container and refrigerate. Record total 24 hour urine volume and collection dates/times on request form. Specimens with no preservative are also acceptable: send entire 24 hour collection to MLabs. Random urine collections not acceptable.

Normal Volume

10 mL aliquot of 24 hour urine collection

Minimum Volume

5 mL aliquot of 24 hour urine collection

Additional Information

Urinary citrate tests for calcium-dependent kidney stones may be run on the same specimen. By ordering "calcium oxalate" the clinician acknowledges that a urine calcium will be performed and billed at a separate additional charge. Hyperoxaluria may occur with high intake of rhubarb, beans, spinach, chocolate, cocoa and tea, with pyridoxine deficiency and occasionally with high ascorbic acid ingestion. Some rare genetic disorders may increase oxalate production. Patients with pancreatic insufficiency, sprue, biliary diversion and who have small intestinal stasis may demonstrate a relationship between fat malabsorption and oxaluria.

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