Update Type: Production schedule change
Test Updated: 10/04/2023
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 Set Up
Every other week, Wednesday.
Analytic Time

8 hours

Soft Order Code
MiChart Code
Oxalate, 24 HR Urine
  • Calcium Oxalate
  • Oxalic Acid
  • Oxalic Acid, Urine
Chemical Pathology
Special Chemistry
Specimen Requirements
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.

Alternate Specimen
May be collected in plain (no preservative) container and acid added at the end of collection. It is preferred to have acid added as soon as possible at the client site, mixed very well, and an aliquot sent. It is very important to mix well with acid prior to aliquotting to dissolve any crystals that may have formed. If acid cannot be added at the client site, the entire collection must be sent. [rev 9/08]
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.

CPT Code
Fee Code