Understanding Your Medical Test: Purpose, Procedure, Preparation, and Possible Risks
A test that measures the amount of calcium in your urine collected over a 24-hour period to evaluate calcium metabolism and kidney function.
{"Measures calcium excreted in urine over 24 hours","Helps diagnose kidney stones, bone diseases, and parathyroid disorders","Requires collecting all urine in a special container for 24 hours","High results may indicate hypercalciuria; low results may indicate hypocalciuria","Follow specific collection instructions carefully for accurate results"}
Key facts at a glance
- LOINC
- 14637-3
- Short code
- U-Ca24hr
- Synonyms
- Calcium 24h Ur-sRate
- Category
- electrolyte
- Sample
- urine
- Container
- 24-hour urine collection container with preservative (e.g., HCl or thymol) or clean container without preservative if refrigerated
- Units
- not specified
- Ref low
- 2.5
- Ref high
- 7.5
- Critical range
- 6 not specified – 14 not specified
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- Atomic Absorption Spectroscopy (AAS) or Spectrophotometry using Arsenazo III dye
- CPT
- 82340
- SNOMED
- 314896005
- Specimen volume
- Minimum 10-20 mL from well-mixed 24-hour collection required for analysis
- Stability
- Room temperature: 24-48 hours; Refrigerated (2-8°C): 5-7 days; Frozen (-20°C): >30 days
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 24–72 hours
- Order
- routine
What is this test? This test is used to evaluate a specific aspect of your health and may help your healthcare provider diagnose a condition, monitor treatment, or guide next steps.
The 24-Hour Urine Calcium test measures the total amount of calcium excreted in your urine over a 24-hour period. Calcium is an essential mineral that plays important roles in bone health, nerve function, and muscle contraction. Normally, your kidneys filter calcium from the blood, and some of it is excreted in urine while the rest is reabsorbed back into the bloodstream.
How is the test performed? Your healthcare professional will explain the procedure, collect the necessary information or sample, and use approved methods to analyze the results safely and accurately.
You will receive a special collection container from your healthcare provider. On the day of collection: 1) Start by urinating into the toilet when you wake up (this first morning urine is not collected). 2) For the next 24 hours, collect ALL urine in the provided container. 3) Keep the container refrigerated or in a cool place. 4) At the end of 24 hours, urinate one final time into the container. 5) Return the container to the lab as instructed. It is important to collect every urine sample during the 24-hour period for accurate results.
Why might I need this test? You may need this test because of symptoms, a routine evaluation, an existing medical condition, treatment monitoring, or a need for more information about your health.
Your doctor may order this test if you have symptoms or conditions such as: kidney stones, bone disease (osteoporosis or osteomalacia), parathyroid disorders, certain types of cancer, or unexplained high or low calcium levels in blood. It is also used to monitor treatment effectiveness for conditions affecting calcium metabolism.
Are there any risks or preparations? Preparation and risks depend on the specific test, so follow your healthcare provider’s instructions and ask whether you should adjust food, medicines, activity, or appointments.
There are no significant risks associated with this test. However, you should: follow your normal diet unless instructed otherwise by your doctor, avoid taking vitamin D or calcium supplements for 24 hours before and during collection unless directed, inform your doctor about all medications you are taking, and keep the urine collection container clean and refrigerated. Certain medications such as diuretics, antacids, and lithium can affect test results.
Reference range
2.5-7.5 mmol/24 hnot specified
Complete 24-hour urine collection required; refrigerate during collection; avoid calcium supplements if directed by clinician
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated urine calcium (hypercalciuria) may indicate: kidney stones, hyperparathyroidism, certain cancers, osteoporosis, vitamin D excess, or use of certain medications. Low urine calcium (hypocalciuria) may indicate: vitamin D deficiency, hypoparathyroidism, kidney disease, or malnutrition. This test helps doctors distinguish between different causes of abnormal blood calcium levels and guide appropriate treatment.
Frequently asked questions
What happens if I miss a urine sample during the 24-hour collection?
Can I exercise during the collection period?
What do abnormal results mean?
How long does it take to get results?
Sources
- 1
- 2Mayo Clinic - UrinalysisSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy