CALCIUM - 24 HOURS URINE

The CALCIUM - 24 HOURS URINE test measures the total amount of calcium excreted in urine during a complete 24-hour period. Calcium is an essential mineral required for strong bones and teeth, normal muscle contraction, nerve function, blood clotting and heart activity. The kidneys help maintain calcium balance by filtering calcium from the blood and returning or eliminating it according to the body's needs.

A single urine sample can vary considerably depending on hydration, meals and the time of day. Collecting every urine specimen over 24 hours provides a more representative measurement of daily calcium excretion. The result helps doctors assess abnormal calcium metabolism and investigate conditions involving the kidneys, bones, parathyroid glands or digestive system.

Excessive urinary calcium is called hypercalciuria and may increase the risk of calcium-containing kidney stones. Low urinary calcium is called hypocalciuria and can occur with low calcium intake, reduced intestinal absorption, vitamin D deficiency, certain kidney disorders or familial conditions. The result does not identify the cause by itself and should be interpreted with blood tests, clinical findings and an assessment of collection completeness.

Benefits of the Test

• Measures total calcium excreted in urine during an entire day.
• Supports evaluation of recurrent or suspected calcium-containing kidney stones.
• Helps investigate high or low calcium concentrations in the blood.
• Provides information about parathyroid, kidney and bone-related disorders.
• May support evaluation of intestinal calcium absorption and vitamin D-related conditions.
• Helps monitor dietary measures or medicines used to manage abnormal urinary calcium.

Why Doctors Recommend This Test

A doctor may recommend this test for people with recurrent kidney stones, blood in the urine, flank pain or imaging findings suggesting urinary stones. Measuring urinary calcium can help determine whether excessive calcium excretion contributes to stone formation and may guide dietary or medication-based prevention.

The test may also be ordered when blood calcium is abnormally high or low. It can contribute to the evaluation of primary hyperparathyroidism, hypoparathyroidism, vitamin D disorders, sarcoidosis, kidney disease, certain inherited calcium-handling conditions and abnormal intestinal absorption.

In selected patients with osteoporosis or unexplained reduction in bone density, the test can help determine whether excessive calcium is being lost through the kidneys. Doctors may repeat it to monitor the response to changes in sodium or calcium intake, thiazide medicines or other treatments. Urinary calcium results must be assessed with serum calcium, creatinine, parathyroid hormone, vitamin D and other relevant findings.

Preparation Before Test

Follow the doctor's dietary and medication instructions. Do not deliberately increase or restrict calcium, salt or fluid intake unless specifically advised, because major changes can affect the result. Inform the healthcare provider about calcium and vitamin D supplements, antacids, diuretics, lithium and all other medicines. Do not stop prescribed treatment without medical advice.

Obtain the correct 24-hour urine container from Focus Diagnostics. On the starting day, empty the bladder into the toilet immediately after waking and record that time; this first urine is not collected. After that, collect every urine passed during the next 24 hours in the provided container. At the same time the following morning, collect the final urine and add it to the container.

Keep the container tightly closed and refrigerated or stored according to the laboratory's instructions throughout the collection. Avoid contamination with stool, menstrual blood, tissue paper or water. If any urine is missed, spilled or collected outside the prescribed period, inform the laboratory because the collection may need to be repeated. Return the complete specimen promptly and provide the recorded start and finish times.

Normal Reporting Time

This is a routine biochemistry measurement and is commonly reported on the same day or within 24 hours after the completed 24-hour collection reaches the laboratory. The collection itself requires a full day, and the exact reporting time may vary with laboratory workflow, specimen condition and the need for verification.

Who Should Take This Test?

The test may be suitable for individuals with recurrent kidney stones, unexplained high or low blood calcium, suspected parathyroid disease, reduced bone density or an abnormal calcium metabolism result. It may also be advised for people undergoing investigation of vitamin D disorders, intestinal malabsorption, kidney disease or an inherited calcium-handling condition.

Patients receiving treatment for excessive urinary calcium may undergo repeat testing to assess their response. This test should be ordered and interpreted by a qualified healthcare professional because age, diet, kidney function, medicines and collection accuracy can influence results.

Detailed Information

Calcium balance depends on dietary intake, intestinal absorption, bone storage, kidney handling, vitamin D and parathyroid hormone. Parathyroid hormone helps regulate blood calcium by influencing the bones, kidneys and activation of vitamin D. When this system is disturbed, urinary calcium can become abnormally high or low.

High urinary calcium may occur with idiopathic hypercalciuria, primary hyperparathyroidism, excessive vitamin D activity, high sodium intake, certain cancers, sarcoidosis, prolonged immobility or some medicines. It can increase the concentration of calcium in urine and promote the formation of calcium oxalate or calcium phosphate stones.

Low urinary calcium may occur with low dietary intake, vitamin D deficiency, malabsorption, impaired kidney function, hypoparathyroidism or familial hypocalciuric hypercalcaemia. Distinguishing familial hypocalciuric hypercalcaemia from primary hyperparathyroidism may require simultaneous blood and urine calcium and creatinine measurements and calculation of a calcium-to-creatinine clearance ratio.

Reference ranges vary by age, sex, dietary calcium, laboratory method and clinical context. A low result can also be caused by an incomplete collection, while excessive collection time can falsely increase the measured total. The laboratory may measure 24-hour urine creatinine to help assess whether the collection appears complete.

A result outside the reference interval does not independently diagnose a disease. The doctor may recommend serum calcium, ionised calcium, phosphate, creatinine, parathyroid hormone, vitamin D, urine oxalate, citrate, uric acid or sodium testing. Results should be reviewed with a healthcare professional before changing diet, supplements or medicines.