Most urine chemistry tests require a 24-hour collection. Record on the test request form any medications that the patient is receiving. If a preservative is required, it is important that the designated preservative be in the urine collection container at the start of the collection. When the 24-hour urine output is less than 1 liter, 4 grams of boric acid can be used when boric acid is the specified preservative or 10 mL of 6N HCl can be used when HCl is specified. The patient (or responsible individual) should be cautioned that the preservative may be toxic and caustic, and not to spill or discard the preservative.
On the day of the collection, discard the first morning urine void, and begin the collection after this void. Collect all urine for the next 24 hours so that the morning urine void on the second day is the final collection. Measure the total 24-hour urine volume. Record this volume on the test request form and on the urine transport vial (see Pediatric Specimen Tubes below). Transfer the requested volume into the labeled urine transport vial. Do not send the entire urine collection.