Hyperoxaluria (hi-pur-ok-suh-LU-ree-uh) happens when you have too much oxalate in your urine. Oxalate is a natural chemical the body makes. It's also found in some foods. But too much oxalate in the urine can cause serious problems.

Hyperoxaluria can be caused by a change in a gene, an intestine disease or eating too many foods that are high in oxalate. The long-term health of your kidneys depends on finding hyperoxaluria early and getting it treated quickly.

Oxalosis (ok-suh-LOW-sis) happens after the kidneys stop working well in people who have primary and intestine-related causes of hyperoxaluria. Too much oxalate collects in the blood. This can lead to oxalate buildups in blood vessels, bones and organs.


Often, the first sign of hyperoxaluria is a kidney stone. Kidney stone symptoms can include:

  • Sharp pain in the back, side, lower stomach area or groin.
  • Urine that looks pink, red or brown due to blood.
  • Frequent urge to pee, also called urination.
  • Pain when peeing.
  • Not being able to urinate or peeing only a small amount.
  • Chills, fever, upset stomach or vomiting.

When to see a doctor

It's not common for children to get kidney stones. Kidney stones that form in children and teenagers are likely to be caused by a health problem, such as hyperoxaluria.

All young people with kidney stones should have a checkup. The checkup should include a test that measures oxalate in the urine. Adults who keep getting kidney stones also should be tested for oxalate in the urine.


Hyperoxaluria happens when too much of a chemical called oxalate builds up in the urine. There are different types of hyperoxaluria:

  • Primary hyperoxaluria. This type is a rare inherited disease, which means that it's passed down in families. It's caused by changes in a gene. With primary hyperoxaluria, the liver doesn't make enough of a certain protein that prevents too much oxalate from being made. Or the protein doesn't work as it should. The body gets rid of excess oxalate through the kidneys, in urine. The extra oxalate can combine with calcium to form kidney stones and crystals. These can damage the kidneys and cause them to stop working.

    With primary hyperoxaluria, kidney stones form early. They most often cause symptoms from childhood through age 20. The kidneys of many people with primary hyperoxaluria stop working well by early to middle adulthood. But kidney failure can happen even in babies with this disease. Others with primary hyperoxaluria may never have kidney failure.

  • Enteric hyperoxaluria. Some intestine problems cause the body to absorb more oxalate from foods. This can then increase the amount of oxalate in the urine. Crohn's disease is one intestine problem that can lead to enteric hyperoxaluria. Another is short bowel syndrome, which can happen when parts of the small intestine are removed during surgery.

    Other health problems make it hard for the small intestine to absorb fats from food. If this happens, it might leave oxalate more available for the gut to absorb. Usually, oxalate combines with calcium in the gut and exits the body through stools. But when there is increased fat in the gut, calcium binds to the fat instead. This allows oxalate to be free in the gut and absorbed in the bloodstream. It's then filtered by the kidneys. Roux-en-Y gastric bypass surgery also can lead to trouble absorbing fat in the gut, which raises the risk of hyperoxaluria.

  • Hyperoxaluria tied to eating foods with lots of oxalate. Eating large amounts of foods high in oxalate can raise your risk of hyperoxaluria or kidney stones. These foods include nuts, chocolate, brewed tea, spinach, potatoes, beets and rhubarb. It's important to stay away from high-oxalate foods if you have diet-related or enteric hyperoxaluria. Your doctor also may tell you to limit these foods if you have primary hyperoxaluria.


Without treatment, primary hyperoxaluria can damage the kidneys. Over time the kidneys may stop working. This is called kidney failure. For some people, this is the first sign of the disease.

Symptoms of kidney failure include:

  • Peeing less than usual or not peeing at all.
  • Feeling ill and tired.
  • Not feeling hungry.
  • Upset stomach and vomiting.
  • Pale, ashen skin or other changes to skin color tied to having a low number of red blood cells, also called anemia.
  • Swelling of hands and feet.

Oxalosis happens if you have primary or enteric hyperoxaluria and your kidneys stop working well enough. The body can no longer get rid of the extra oxalate, so the oxalate starts building up. First it builds up in the blood, then in the eyes, bones, skin, muscles, blood vessels, heart and other organs.

Oxalosis can cause many health problems outside the kidneys in its late stages. These include:

  • Bone disease.
  • Anemia.
  • Skin ulcers.
  • Heart and eye problems.
  • In children, serious problems developing and growing.

Hyperoxaluria and oxalosis care at Mayo Clinic

May 11, 2023
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