The causes for a blue or purple colored urine are limited.


Reasons for a bluish colored urine:

(1) biliverdiin

(2) indigo blue, indigo carmine or other dye

(3) methylene blue

(4) triamterene


In urine drug testing a blue dye is added to the toilet bowl water, which may rarely be submitted by the person being tested (perhaps someone who is color blind)


Reasons for a purplish urine:

(1) phenolphthalein (with urine acidic; red with alkaline urine)


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