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Urine Calcium, 24-Hour

How much calcium your kidneys release into urine over a full day. It helps explain kidney stones and calcium or bone problems.

AI-verified against cited sources. Awaiting expert reviewAlso called 24h UCaLOINC 6874-2

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The usual range for 24-h urine calcium depends on sex. Choose female or male above to see where you stand.

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What it is

Calcium is a mineral your body uses for bones, nerves, muscles and your heart. Your kidneys filter calcium out of your blood and take most of it back, and the rest leaves in your urine. This test measures all the calcium in your urine over 24 hours, which shows how much your body releases in a typical day. The result depends a lot on what you eat, especially salt, protein and calcium, and on hormones such as parathyroid hormone (PTH) and vitamin D.

Why it matters

A 24-hour urine calcium is a main test for people who get kidney stones. About 80% of kidney stones contain calcium, and high urine calcium is the most common metabolic finding in people who keep forming calcium stones. The test also helps clinicians look into high or low blood calcium, parathyroid problems and bone disease. It is often part of a larger kidney stone panel with oxalate, citrate, urine volume and pH. The result is a clue about risk, not a diagnosis. Stone risk rises gradually with urine calcium, and experts don't agree on one cutoff.

If it’s low

A lower result usually reflects low calcium intake, calcium that isn't absorbed well from food, or the way your kidneys hold on to calcium. It is often harmless and fits a low-calcium diet. A few conditions cause it, so your clinician will read it alongside your blood calcium, vitamin D and PTH.

Common causes

  • Eating little calcium
  • Conditions that make it hard to absorb nutrients from food, or malnutrition
  • Severe vitamin D deficiency
  • Thiazide diuretics, a type of water pill that helps kidneys hold on to calcium
  • Underactive parathyroid glands (hypoparathyroidism)
  • Kidney disease
  • Familial hypocalciuric hypercalcemia, an inherited condition that raises blood calcium but usually keeps urine calcium low

What can help

  • Ask whether your calcium intake and vitamin D level are in a good range
  • Ask whether blood calcium, vitamin D or PTH tests would help explain the result
  • Ask whether any of your medicines or supplements could be affecting your urine calcium

If it’s high

A higher result means more calcium is passing out through your kidneys than your lab's usual limit. It is common in people who form calcium kidney stones, and diet often plays a part. It can also be a sign that your parathyroid glands, vitamin D level or bones need a closer look, so your clinician will read it together with your blood calcium.

Common causes

  • A diet high in salt (sodium) or animal protein
  • Idiopathic hypercalciuria, meaning high urine calcium with no other cause found, which is the most common finding in people who keep forming calcium stones
  • Calcium supplements or calcium-based antacids
  • Too much vitamin D
  • Loop diuretics, a type of water pill
  • Overactive parathyroid glands (hyperparathyroidism)
  • Sarcoidosis
  • Some bone conditions, and rarely some cancers that involve bone
  • Some kidney conditions

What can help

  • Ask your clinician whether eating less salt and less animal protein could help, since both raise urine calcium
  • Ask before cutting back on calcium-rich foods. Eating less calcium can raise the oxalate your body absorbs, which can make stones more likely
  • Review your calcium and vitamin D supplements, antacids and other medicines with your clinician
  • Ask whether your blood calcium and PTH should be checked
  • Ask what daily fluid and urine-volume goal makes sense for you

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on sex. Choose women or men to see the one that applies.

ESE 2022 consensus hypercalciuria cut-off for women (more than 250 mg/24 h; definitions vary)

  • Below the hypercalciuria cut-offbelow 250 mg/24 h
  • Above the hypercalciuria cut-off250 and above mg/24 h

ESE 2022 consensus hypercalciuria cut-off for men (more than 300 mg/24 h; definitions vary)

  • Below the hypercalciuria cut-offbelow 300 mg/24 h
  • Above the hypercalciuria cut-off300 and above mg/24 h

What can affect your result

  • Salt (sodium) and animal protein intake raise urine calcium
  • Calcium intake: ARUP lists 50-150 mg/day on a low-calcium diet, 100-250 on an average diet (about 800 mg/day) and above 250 on a high-calcium diet
  • Sex: Mayo's upper limit is 250 mg/24 h for men and 200 mg/24 h for women
  • Body size: stone care also uses a weight-based cut-off of 4 mg/kg/24 h
  • Whether the 24-hour collection was complete, and how the urine was kept
  • Medicines and supplements, including calcium, vitamin D, antacids, loop diuretics and thiazide diuretics
  • Hormones and bone health, including parathyroid hormone and vitamin D
  • An incomplete or over-long collection changes the total. Labs often check urine creatinine to judge completeness (about 15-20 mg/kg/day in women and 20-25 mg/kg/day in men).
  • What you eat during the collection matters. More salt (sodium) or animal protein raises urine calcium, and calcium intake does too, so a 24-hour test is usually done on your usual diet.
  • Calcium or vitamin D supplements and calcium-based antacids can raise the result. Loop diuretics (a type of water pill) can raise it, and thiazide diuretics tend to lower it.
  • Labs differ on preservative. ARUP asks for acid (pH 1.5-2.0), while Mayo's kidney stone profile prefers a different preservative and does not accept acid or a warm, unpreserved container. Use the container and instructions your lab gives you.

A timed 24-hour collection. Empty your bladder to start and throw that urine away, then collect every drop for the next 24 hours, including the first urine the next morning. Keep the container cold (refrigerator or cooler) and follow your lab's directions about any preservative. Reflects the 24 hours you collected. It can shift with changes in diet, salt intake, supplements or medicines.

When to talk to a clinician

A urine calcium result on its own is not an emergency. Talk with the clinician who ordered it about any result outside your lab's range. See a clinician promptly for sharp pain in your side, back, lower belly or groin, blood in your urine, pain when you urinate, or fever and chills, since these can go with a kidney stone or an infection. Get urgent care if you can't urinate at all or only pass a little.

Questions you could ask

  • Was my 24-hour collection complete, based on the creatinine?
  • Should we repeat the collection to confirm the result?
  • How does this fit with my other kidney stone panel results?
  • Could my salt or protein intake explain this result?
  • Should we check my blood calcium and PTH?
  • Could any of my supplements or medicines be raising my urine calcium?

Questions people ask

Why do labs give different upper limits for urine calcium?

There is no single agreed cutoff. Some labs use 250 mg per day for men and 200 for women, others show 100-250 for everyone, and stone specialists often use 250 or 300 mg per day, or 4 mg per kg of body weight. Urine calcium also follows what you eat, so the same person can land in different places on different days.

Should I cut calcium from my diet if my urine calcium is high?

Ask your clinician first. A review of kidney stone nutrition advises against restricting dietary calcium, because eating less calcium can raise the oxalate your body absorbs. Cutting back on salt and animal protein is often discussed instead.

How do I convert mg per 24 hours to mmol per 24 hours?

Divide the mg value by 40.08. For example, 250 mg/24 h is about 6.2 mmol/24 h. To go the other way, multiply mmol by 40.08.

Show the science and sources

Units

  • 1 mg/24 h = 1 mg/24 h
  • 1 mg/24 h = 0.02495 mmol/24 h

Open the 24-h urine calcium unit converter

Is a change real?

24-h urine calcium naturally varies about 27.5% from test to test in the same healthy person. Between two results from the same lab, a rise of 131% or more, or a fall of 57% or more, is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Desirable Biological Variation Database specifications, 2014 update (Minchinela J, Ricos C, et al.; the 'Ricos database', a compilation of median published CVI/CVG).

For clinicians and researchers

Reported as mg/24 h (LOINC 6874-2, mass per time) or mmol/24 h (14637-3); multiply mmol by 40.08 to get mg. Some labs also print the concentration in the collection (mg/dL). Reference limits differ: Mayo's stone profile prints <250 mg/24 h for men and <200 mg/24 h for women, ARUP prints 100-250 mg/24 h on an average (about 800 mg/day) diet with diet-specific intervals, and MedlinePlus gives 100-250 mg/day with values above 300 mg/day called high. In stone care, hypercalciuria is variably defined as more than 200-300 mg/day, as more than 250 mg/24 h in women and 300 mg/24 h in men, or as more than 4 mg/kg/24 h (ESE 2022; AJKD 2023). The AJKD Core Curriculum notes a graded rise in stone risk from about 150 mg/day, advises reading 24-hour values as continuous risk variables rather than absolute thresholds, and suggests correlating with urine sodium to see whether salt intake drives the calcium. Excretion reflects intestinal absorption, bone turnover and tubular reabsorption (PTH, vitamin D, loop and thiazide diuretics, the calcium-sensing receptor). Primary hyperparathyroidism, vitamin D excess and sarcoidosis tend to raise it. Familial hypocalciuric hypercalcemia typically shows low urinary calcium, and ESE 2022 uses a calcium-to-creatinine clearance ratio under 0.01 as a screen for it. Restricting dietary calcium can increase intestinal oxalate absorption and urine oxalate (Clin Nutr Res 2015). Creatinine excretion is used to check collection completeness.

LOINC 6874-2 (primary), 14637-3, 18488-7, 25362-5. Specimen: urine-24h.

Sources

  1. Supersaturation Profile, 24 Hour, Urine (Mayo test SUP24), Mayo Clinic Laboratories
  2. Calcium, Urine (ARUP test 0020472), ARUP Laboratories
  3. Calcium - urine (MedlinePlus Medical Encyclopedia), MedlinePlus, U.S. National Library of Medicine (2025)
  4. Calcium in Urine Test (MedlinePlus Medical Test), MedlinePlus, U.S. National Library of Medicine
  5. Nutritional Management of Kidney Stones (Nephrolithiasis), Clinical Nutrition Research (2015)
  6. Kidney Stone Pathophysiology, Evaluation and Management: Core Curriculum 2023, American Journal of Kidney Diseases (2023)
  7. European expert consensus on practical management of specific aspects of parathyroid disorders in adults and in pregnancy: recommendations of the ESE Educational Program of Parathyroid Disorders (PARAT 2021), European Journal of Endocrinology (European Society of Endocrinology) (2022)
  8. Calcium (PubChem compound 5460341), PubChem, U.S. National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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