Specimen Collection:
At the start of the 24 hour collection, discard first morning urine, from that time collect all urine for 24 hours adding 5g sodium carbonate (Na2CO3) to the jug at the start, this will adjust the pH to a range of 6-7. Urine must be kept refrigerated during collection or kept on ice. Once 24 hour collection is complete, record total volume of urine, mix well, then aliquot 2.0 mL to a screw top container, protect from light and send refrigerated. Indicate total volume of 24 hour urine on aliquot and requisition before shipping.

Whenever possible, the specimen should be collected during an acute episode because porphobilinogen (PBG) may decrease rapidly upon remission. PBG may also degrade when samples are exposed to UV light for extended periods, or are transported at ambient temperature. If an amber collection jug/urine cup is not available, the sample must be protected from light by completely wrapping the container in aluminum foil. Twenty-four hour specimens should be refrigerated and protected from UV light during collection. PBG is most stable at pH 6-7. All results should be interpreted in the context of clinical findings, relevant history, and other laboratory data.