Laboratory Test Overview: What This Test Measures, Why Your Healthcare Provider May Order It, How to Prepare, How the Sample Is Collected, and What Your Results Mean

What is this laboratory test, what does it measure in your body, and how can it help your healthcare provider understand your health or guide care decisions?

The urine calcium test measures the concentration of calcium in your urine. Calcium is an essential mineral that plays a crucial role in bone health, muscle function, nerve signaling, and blood clotting. Your body carefully regulates calcium levels through a balance of absorption in the intestines, storage in bones, and excretion through kidneys. This test helps doctors understand how well this balance is working.

Why is this laboratory test performed, and what symptoms, illnesses, medications, pregnancy concerns, chronic conditions, or routine health goals can it help evaluate?

Your doctor may order a urine calcium test to evaluate several conditions: to investigate the cause of kidney stones, to assess parathyroid gland function, to monitor bone diseases such as osteoporosis or osteomalacia, to evaluate kidney function, or to check for certain metabolic disorders. It may also be used to monitor the effects of certain medications that affect calcium levels.

How should you prepare for this laboratory test, and what should you ask your healthcare provider about fasting, food, water, medications, supplements, or activity before the sample is collected?

Your doctor may ask you to follow specific instructions before the test. You may need to temporarily stop taking certain medications such as diuretics, antacids, or calcium supplements. You might also be asked to maintain your normal diet or follow a specific calcium intake for a period before the collection. It's important to follow these instructions carefully for accurate results. Inform your doctor about all medications and supplements you are taking.

How is the sample for this laboratory test collected, and what should you expect if the sample is blood, urine, stool, saliva, or another body sample taken at a clinic or laboratory visit?

For a 24-hour urine collection, you will receive a special container from the laboratory. On the morning of collection, start by urinating into the toilet and note the time. Collect all urine for the next 24 hours in the provided container, including the final morning urine on day two. Store the container in a cool place or refrigerator during collection. For a single urine sample, simply provide a clean-catch midstream urine sample in a sterile container.

What do the results of this laboratory test mean, and how might your healthcare provider interpret reference ranges, trends, symptoms, and other findings to decide whether the result is normal, abnormal, or needs follow-up?

Results are typically reported as milligrams (mg) or millimoles (mmol) of calcium per liter of urine over 24 hours. High urine calcium (hypercalciuria) may indicate kidney stones, hyperparathyroidism, certain cancers, sarcoidosis, or excessive vitamin D intake. Low urine calcium (hypocalciuria) may be due to hypoparathyroidroidism, vitamin D deficiency, kidney disease, or certain medications. Your doctor will interpret your results in context with your overall health, symptoms, and other test results.