This is a urine test to see if you have a high level of the chemical oxalate in your urine. Oxalate is a natural end product of metabolism in the body. It should leave your body through your urine. If your oxalate levels are too high, the extra oxalate can combine with calcium to form kidney stones. These stones are hard masses of chemicals that can get stuck in the urinary tract. They commonly cause severe pain. Calcium-oxalate kidney stones are the most common type. Higher levels of oxalate may be caused by eating foods high in oxalate, or by your body absorbing or making too much oxalate.
You may need this test if you have kidney stones often. Your healthcare provider might order this test to help them advise you on treatment. It may also be used to find out how well limiting the amount of oxalate in your food is working. You might have this test to see if you have a rare inherited condition called primary hyperoxaluria and are at an increased risk of developing kidney stones.
You might also need tests to look for other chemicals in your urine: glycolate and glycerate. A blood sample may also be needed to test for a genetic form of hyperoxaluria.
Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you.
The normal level of urine oxalate excretion is less than 45 milligrams per day (mg/day). A higher level of urine oxalate may mean you are at risk of developing kidney stones. Risk of stone formation seems to increase even at levels above 25 mg/day, which is considered a normal level.
This test needs a 24-hour urine sample. For this sample, you must collect all of your urine for 24 hours. Empty your bladder completely first in the morning without collecting it. Note the time. Then collect your urine every time you go to the bathroom over the next 24 hours.
Eating foods high in vitamin C can affect your test results. In the body, vitamin C is changed into oxalate. Your test results also may be affected by an inflammation of the bowel or if you've had intestinal or colon surgery. Eating spinach, peanuts, chocolate, and other foods high in oxalate may increase oxalate in your urine.
Don't eat or drink any food with vitamin C for 24 hours before you collect your urine sample. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.