Collect 24 hour urine specimen. Add 25 mL of 50% glacial acetic acid (15 mL for pediatric patients) to container prior to start of collection. Following collection, mix well, measure 24 hour urine volume, aliquot 10 mL into a plastic urine container and refrigerate. Record total 24 hour urine volume and collection dates/times on request form. Specimens with no preservative are also acceptable: add 50% glacial acetic acid to container following collection, mix well and send 10 mL aliquot (preferred); alternatively a non-acidified aliquot will be accepted. Patient should avoid bananas, pineapple, walnuts, chocolate, kiwi, cough medicine and avocados prior to and during collection; also phenothiazines should be withheld for several days prior to collection if possible.