Hypercalciuria
Too much calcium in the urine
Quick Facts
- Type: Metabolic / kidney-related condition
- Main concern: Kidney stones and bone loss
- Common cause: Idiopathic (no single identifiable cause)
- Diagnosis: 24-hour urine calcium test
Overview
Hypercalciuria means that the urine contains more calcium than normal. The kidneys filter calcium from the blood and normally reabsorb most of it, sending only a small amount into the urine. When too much calcium spills into the urine, it can combine with other substances and form crystals, which is why hypercalciuria is one of the most common reasons people develop calcium kidney stones.
Hypercalciuria itself often causes no symptoms and is discovered during the evaluation of kidney stones or blood in the urine. In many people the blood calcium level is normal, and the high urine calcium is the main finding. Over the long term, losing extra calcium in the urine can also affect bone strength.
Symptoms
By itself, hypercalciuria usually produces no symptoms. Most problems come from the complications it can cause, particularly kidney stones.
- Sudden, severe pain in the side or back that may spread to the lower abdomen or groin (renal colic from a stone)
- Blood in the urine, which may be visible or found on testing
- Frequent or painful urination
- Cloudy or strong-smelling urine
- In children, recurrent urinary symptoms or unexplained blood in the urine
Long-standing high urine calcium can contribute to weaker bones, though this develops silently.
Causes
Hypercalciuria can result from how the body handles calcium in the gut, the kidneys, or the bones. In many people no single cause is found, and the condition is called idiopathic hypercalciuria.
- Idiopathic hypercalciuria: The most common type, often running in families, where the kidneys release more calcium for reasons that are not fully understood.
- High calcium absorption: The intestines take up more calcium from food than usual.
- Overactive parathyroid glands: Hyperparathyroidism raises blood calcium and the amount passed in the urine.
- Other causes: High vitamin D intake, certain medications such as some diuretics, prolonged bed rest, and some kidney and bone disorders.
A diet very high in salt or animal protein, or very high in supplemental calcium, can increase urine calcium as well.
Risk Factors
- A personal or family history of kidney stones
- A diet high in salt or animal protein
- High intake of vitamin D or calcium supplements
- Overactive parathyroid glands
- Long periods of immobility
- Certain medications, including some diuretics and steroids
Diagnosis
Hypercalciuria is identified mainly through urine testing, often as part of a kidney stone work-up:
- 24-hour urine collection: The key test, measuring the total calcium passed in the urine over a full day.
- Blood tests: Calcium, parathyroid hormone, and vitamin D levels help find an underlying cause.
- Urinalysis: Checks for blood, crystals, and infection.
- Imaging: Ultrasound or a CT scan looks for kidney stones or calcium deposits in the kidneys.
Treatment
Treatment aims to lower urine calcium, prevent stones, and protect bone, and it depends on the cause.
- Fluids: Drinking plenty of water dilutes the urine and reduces the chance of crystals forming.
- Dietary changes: Lowering salt and limiting animal protein reduce urine calcium; getting a normal (not low) amount of dietary calcium is usually advised, as very low calcium diets can backfire.
- Medications: Thiazide diuretics can reduce the calcium the kidneys release; other medicines target specific causes.
- Treating the underlying problem: For example, surgery for overactive parathyroid glands or adjusting high-dose vitamin D.
A doctor or dietitian can tailor advice based on the 24-hour urine results.
Prevention
- Drink enough water each day to keep urine pale
- Limit salty and highly processed foods
- Avoid excessive animal protein
- Take calcium and vitamin D supplements only as advised, not in large unsupervised doses
- Follow up on kidney stones and any parathyroid or bone conditions
When to See a Doctor
See a doctor if you have repeated kidney stones, unexplained blood in the urine, or recurrent urinary symptoms. Seek urgent care for sudden, severe pain in the side or back, especially with nausea, fever, or difficulty passing urine, which can signal a kidney stone blocking the flow of urine and may need prompt treatment.
Frequently Asked Questions
Does hypercalciuria cause symptoms?
On its own it usually causes no symptoms. Most people learn they have it after developing kidney stones or having blood found in their urine. Long-term calcium loss can also affect bone strength silently.
Should I stop eating calcium if I have hypercalciuria?
No. A normal amount of dietary calcium is usually recommended, because very low calcium diets can actually increase the risk of stones. The more helpful steps are drinking plenty of water and cutting back on salt and excess animal protein.
How is hypercalciuria diagnosed?
The main test is a 24-hour urine collection that measures how much calcium you pass over a full day. Blood tests for calcium, parathyroid hormone, and vitamin D help find an underlying cause, and imaging can check for stones.
Can hypercalciuria be treated with medicine?
Yes. When diet and fluids are not enough, a thiazide diuretic can reduce the calcium your kidneys release into the urine. Other treatments target specific causes, such as surgery for overactive parathyroid glands.
References
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Kidney Stones.
- MedlinePlus, U.S. National Library of Medicine. Urine calcium.
- National Kidney Foundation. Kidney Stones.
- Mayo Clinic. Kidney stones.