Mannitol and Creatinine, Urine/Serum Ratio

What is this test?

Mannitol is a sugar that is normally absorbed and passed in urine. Measuring it along with creatinine, a marker of urine concentration and kidney function, helps clinicians assess intestinal permeability. The results may be reported as a ratio derived from urine and serum measurements.

Why might I need this test?

This test may be used when intestinal lining damage or increased intestinal permeability is suspected, including in the evaluation of gastrointestinal conditions such as celiac disease or inflammatory bowel disease. It may also be used in selected research or specialist settings.

How is the test performed?

You may be given a measured amount of mannitol to drink. Blood and urine samples are then collected according to the laboratory’s protocol, and the mannitol and creatinine results are used to calculate the reported ratio. The collection period and timing are important because incomplete urine collection can affect the results.

How do I prepare for the test?

Follow the laboratory’s instructions about drinking the mannitol solution, fasting, and the exact time for urine collection. Stay normally hydrated unless your clinician directs otherwise, and tell the care team about any illness, vomiting, diarrhea, or kidney problems that could affect the results.