Urinalysis - The Carter Center

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Interfering Factors
It is usually important to consider, that on standing of urine for more than
30 minutes, the urobilinogen that is found in urine will oxidize and
change to urobilin. Thus due to this process, the color of urine becomes
dark. Therefore, the physical examination of urine should be done
immediately after the delivery of urine to the laboratory.
Other interfering factors that result in abnormal urine color formation are
certain foodstuff, and medications.
• Food stuf, such as beets will give white red color.
• Drugs such as Vitamin B 12 and riboflavin will give bright yellow color
to urine.
• Rifampicilin will give red color to urine.
• Iron salt will give dark color to urine.
• Sulfonamides will give rusty yellow or brownish color.
Therefore, when abnormal colored urine is observed, it is important to
ask the patient, what kind of food he consumed in the last 36-24 hrs, and
also whether he used drugs or not. If so, it is important to know what
food and what drug he used.
3.5 Appearance (Transparency)
Fresh voided urine specimen is normally clear and transparent. On long
standing, due to chemical changes that occur in normal constituents of
urine through time, as described in the introduction part of this lecture
note, it becomes turbid.
Procedure of the Test
• Appearance (transparency) of urine can be measured only by
observation of fresh voided urine specimen.