Quick Facts
- Sample: 24-hour urine collection
- Fasting: Not required
- Turn-around: 1–6 business days. May take longer based on weather, holiday, or lab delays.
Benefits
- Prevent kidney stones before they form — identify elevated oxalate levels and your personal stone risk early
- Complete metabolic picture — 24-hour collection captures full daily patterns more reliably than single samples
- Convenient at-home collection — no office visit required; collect samples in your natural environment
- Creatinine normalization included — accounts for hydration status and kidney function for accurate results
- Actionable insights — guides specific dietary changes, hydration targets, and preventive strategies
- Cost-effective screening — avoid expensive emergency visits and surgical procedures later
Who Is This Test For?
- Individuals with a personal or family history of kidney stones
- People experiencing recurrent kidney stone episodes
- Those with chronic diarrhea, inflammatory bowel disease, or post-bariatric surgery
- Patients diagnosed with or suspected of having primary hyperoxaluria
- Adults following high-oxalate diets (spinach, nuts, chocolate, beets)
- Anyone seeking proactive metabolic screening for stone prevention
How It Works – Just 3 Steps
- Order and pickup collection kit - schedule your appointment at a nearby lab and go to pick up your collection kit for urine sample
- Collect 24-hour urine sample - follow simple instructions, refrigerate sample throughout collection.
- Return kit and get results - Return your collection kit to the lab, receive confidential results online.
FAQ
What does this test measure? It measures oxalate (a metabolic waste product) and creatinine levels in your urine over 24 hours. High oxalate increases kidney stone risk; creatinine confirms collection accuracy and kidney function.
How accurate is a 24-hour urine test? Very accurate when collected properly. The 24-hour collection captures complete daily urinary patterns, making it more reliable than spot samples for metabolic assessment (NIH 2024).
What if my oxalate levels are high? Elevated oxalate (>38 mg/24h) indicates increased stone risk. Your doctor may recommend dietary changes, increased hydration (2.5L+ daily), calcium intake adjustments, or medications like potassium citrate (Mayo Clinic 2025).
Can diet alone lower oxalate levels? Yes. Eating adequate calcium with meals (1,000-1,200 mg/day), drinking more water, limiting high-oxalate foods, and reducing sodium can significantly lower urinary oxalate.
Do I need to fast before collecting? No fasting required. Maintain your normal diet and fluid intake during collection for accurate baseline results. Avoid vitamin C supplements exceeding 1,000 mg/day for 48 hours prior.
How often should I retest? If elevated, retest every 3-6 months initially after starting treatment, then every 6-12 months for ongoing monitoring. Normal results may not need repeat testing unless symptoms develop.
More Details
What is the purpose of this test?
The Oxalic Acid, 24-Hour Urine with Creatinine test measures urinary oxalate excretion over 24 hours to identify hyperoxaluria (elevated oxalate), a major risk factor for kidney stone formation. Approximately 9.9% of U.S. adults have experienced kidney stones, with 20-30% of recurrent stone formers showing elevated urinary oxalate. Oxalate is the single strongest chemical promoter of kidney stones—roughly 15-20 times more potent than excess urinary calcium.
This test evaluates your kidney stone risk profile, differentiates between primary hyperoxaluria (inherited metabolic disorder) and secondary hyperoxaluria (dietary or malabsorption-related), and monitors treatment effectiveness. Creatinine measurement normalizes results for urine volume and kidney function, ensuring accurate interpretation. Early detection enables targeted dietary modifications, hydration strategies, and preventive medications before painful stone episodes occur (Mayo Clinic Laboratories 2025).
Who would benefit from this test?
This test provides critical insights for individuals at risk of kidney stones or metabolic disorders:
- Recurrent kidney stone formers — identify the metabolic cause and prevent future episodes
- First-time stone patients — determine if elevated oxalate contributed to stone formation
- Family history of stones — screen for inherited predisposition before symptoms develop
- Primary hyperoxaluria patients — monitor disease progression and treatment response
- Post-bariatric surgery patients — assess malabsorption-related hyperoxaluria risk
- Inflammatory bowel disease (IBD) — detect fat malabsorption causing oxalate overabsorption
- Cystic fibrosis patients — monitor oxalate levels as part of comprehensive care
- High-oxalate diet consumers — evaluate impact of spinach, nuts, chocolate, beets
- Women seeking preventive health — kidney stone prevalence in women increased from 6.5% to 9.1% during 2007-2020
When should I order the Oxalic Acid, 24-Hour Urine with Creatinine test?
Consider ordering this test if you experience or have:
- Recurrent kidney stones — two or more stone episodes warrant metabolic evaluation
- Calcium oxalate stone composition — confirmed by stone analysis
- Unexplained lower back or flank pain — possible stone-related discomfort
- Blood in urine (hematuria) — may indicate stone passage or kidney damage
- Family history of kidney stones — genetic predisposition to hyperoxaluria
- Chronic diarrhea or malabsorption — increases oxalate absorption risk
- Post-gastric bypass surgery — significant hyperoxaluria risk due to altered digestion
- Monitoring treatment response — reassess after dietary changes or medication initiation
For patients on treatment, repeat testing every 3-6 months initially, then every 6-12 months for ongoing monitoring. Those with confirmed primary hyperoxaluria require more frequent assessment, particularly when starting new therapies.
How do I interpret the results?
Your results will show oxalate and creatinine levels measured over 24 hours:
- 3.6–38.0 mg/24h: Normal range — continue healthy habits and maintain hydration
- 38.1–64.0 mg/24h: Mild hyperoxaluria with increased stone risk — adopt dietary changes, increase water intake to 2.5+ L/day, and optimize calcium intake
- 64.1–100.0 mg/24h: Moderate hyperoxaluria, possibly indicating primary hyperoxaluria — pursue further testing (glycolate/glycerate), consider genetic evaluation, and expect possible need for medical therapy
- >100.0 mg/24h: Severe hyperoxaluria, commonly seen in primary hyperoxaluria — requires immediate nephrology referral, genetic testing, and specialized treatments such as vitamin B6 or other therapies
Disclaimer: Reference ranges may vary by laboratory. Listed ranges are general guidelines and may differ from those used by the performing lab. Always consult your healthcare provider for interpretation.
Pre-test preparation
48 hours before collection:
- Avoid high-dose vitamin C supplements (>1,000 mg/day converts to oxalate)
- Limit extreme oxalate intake — moderate consumption of spinach, beets, rhubarb, almonds, chocolate, Swiss chard for baseline assessment
- Continue regular medications — unless instructed otherwise by your healthcare provider
- Maintain normal hydration — drink your usual fluid amount; don't artificially increase or decrease
Collection day:
- Choose a day at home — you'll need access to bathroom facilities throughout 24 hours
- Avoid strenuous exercise — maintain normal activity levels
- Keep sample cool — refrigerate collection container if possible; use cooler with ice packs
- Record all medications and supplements — list everything taken during collection period
Collection procedure: - Start: Upon first morning urination, empty bladder completely into toilet (discard this sample). Record exact start time.
- Collect: For the next 24 hours, collect every drop of urine into the provided container.
- End: Exactly 24 hours later, empty bladder one final time into container. Record exact end time.
- Transport: Deliver to the lab within 24 hours in a cooler with ice packs.
How often should I get tested?
Testing frequency depends on your kidney stone risk and treatment status:
- Initial screening (no stone history): Once; repeat only if symptoms develop
- First kidney stone episode: Once after stone passes; repeat in 3–6 months if elevated
- Recurrent stone former (2+ episodes): Every 6–12 months for ongoing monitoring
- Starting new treatment (diet/medication): Retest at 3 months, then again at 6 months to confirm effectiveness
- Confirmed primary hyperoxaluria: Every 3–12 months depending on severity and treatment plan
- Post-bariatric surgery or IBD: Annually or as symptoms warrant
Patients with elevated oxalate should repeat testing every 3-6 months initially after starting treatment, then every 6-12 months for ongoing monitoring. A decrease in urine oxalate of at least one-third indicates definite response to treatment.
Why early detection matters
Kidney stone disease affects nearly 10% of U.S. adults and imposes substantial healthcare costs through emergency visits, hospitalizations, and surgical interventions. Early metabolic screening identifies hyperoxaluria before painful stone episodes occur, enabling preventive interventions that dramatically reduce stone recurrence.
Prevention is highly effective: Research demonstrates that potassium-magnesium citrate combination therapy reduced stone recurrence by approximately 95% in calcium stone formers (AUA News 2022). Simple dietary modifications—adequate calcium intake, increased hydration, sodium reduction—can lower urinary oxalate significantly without medication.
Protecting kidney function: Recurrent kidney stones can lead to chronic kidney disease over time. Primary hyperoxaluria, if undiagnosed, causes progressive kidney damage and may require dialysis or transplantation. Early detection through 24-hour urine testing allows intervention before irreversible damage occurs.
Improving quality of life: Kidney stone pain is debilitating. Proactive screening and prevention eliminate the severe pain, missed work, emergency visits, and anxiety associated with recurrent stone episodes. For individuals with family history or risk factors, testing provides peace of mind and actionable health insights (Mayo Clinic 2025).
Related tests you may consider
Kidney #3 Extreme Blood and Urine Test Panel — Helps detect complex metabolic or renal abnormalities that may influence urinary oxalate levels.
Magnesium, 24-Hour Urine Test — Assesses urinary magnesium, a natural inhibitor of calcium oxalate crystallization.
Calcium, 24-Hour Urine Test — Evaluates urinary calcium levels, a key factor in calcium-oxalate stone formation and often assessed alongside urinary oxalate.
