Folic acid is the coenzyme for the conversion of FIGLU to glutamate. Block in this step leads to increased excretion of FIGLU in urinrFIGLU Excretion Test It is a sensitive indicator for folic acid deficiency. About 5 g of histidine is given three times at 4hourly intervals. Urine is collected for 24 hours after the initial dose. Normally less than 30 mg of FIGLU is excreted per day; the value is increased in folate deficiency.Reference Textbook of Biochemistry DM Vasudevan 7th edition: page no 244