Urine may appear dark brown or black if certain compounds are present. Sometimes the darkening occurs only after the urine has stood for several hours under conditions favoring oxidation (sunlight, air).

Darken on Standing (Oxidation)


melanogenuria (melanuria)

metastatic melanoma or Addison's disease, hemochromatosis (see previous section)


converted from hemoglobin, especially if urine acid

gentisic acid

metabolite of salicylates

homogentisic acid

in alkaptonuria, especially if urine alkaline

indican (indol-3-yl sulfate, 3-indoxysulfuric acid)

metabolite of tryptophan, seen in stagnant small bowel contents

phenol poisoning



yellow foam, jaundiced


Drugs causing brown or black urine:

(1) furazolidone

(2) iron sorbitol

(3) levodopa

(4) methyldopa (especially if oxidizing agents present)

(5) metronidazole

(6) nitrofurantoin

(7) phenacetin

(8) methocarbamol


Other causes:

(1) povidone iodine

(2) rhubarb

(5) tyrosinosis

(6) senna (leaves of Cassia senna used as a cathartic)

(7) nitrites


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