inulin /in″yo͝olin/ , a fructose-based starch derived from rhizomes of plants from the Compositae family. It is used as a diagnostic aid in tests of kidney function, specifically glomerular filtration. It is not metabolized or absorbed by the body. It is freely filtered by the glomeruli of the kidney but is neither secreted nor reabsorbed by the tubules, making its clearance equivalent to the glomerular filteration rate.
