In a healthy person, the hemoglobin is filtered and then reabsorbed by the kidneys to prevent any loss of hemoglobin through the urine. Patients with hemolytic anemia have a higher level of free hemoglobin in plasma, because of the high destruction of the red blood cells which causes the hemoglobin to be released into the plasma. This higher amount of free hemoglobin cannot fully be reabsorbed by the kidneys and a part of it appears in the urine. Hemoglobin has a bright red color and gives the urine a darker, red-brown color. Having hemoglobin in urine is called hemoglobinuria.

”Especially in the morning, my urine is really dark. I thought this was normal until I once saw the urine of my partner and saw the big difference in colour. Now we make fun of it”
Female, 28 years

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