Although it can cause concern, the appearance of black urine is most often caused by minor changes, such as eating some foods or using new medications prescribed by the doctor.
However, this color of urine can also be caused by more serious health problems, such as porphyria or even skin cancer. Thus, if black urine appears for more than 2 days or if it is accompanied by other symptoms, it is advisable to go to the general practitioner to identify the cause and start the appropriate treatment.
3 main causes of black urine
Changes in urine color usually have 3 main types of causes:
1. Intake of some foods
This is the least worrying cause of the appearance of black urine and is related to the excessive intake of foods with natural or artificial colors such as:
- Rhubarb: usually causes only darker urine, but in very high amounts it can cause the urine to turn black; Broad beans: they are rich in L-dopa, a substance that makes urine darker, brown or black; Aloe, in the form of juice, for example: contains aloin, a substance that can make urine black.
In addition, foods rich in sorbitol, such as apples, pears, peaches and plums, as well as sugar-free foods such as gum, ice cream or candies can also change the color of urine to black. However, when sorbitol is in very high amounts it also causes stomach pain, cramps and diarrhea.
The use of copper pots for cooking can also cause black urine in some people, especially those who cannot metabolize the mineral, eliminating it in high amounts in the urine, which makes the urine very dark.
What to do: If the person realizes that the urine turned black after a meal rich in this type of food, although it is not a concern, it is recommended to avoid the consumption of these foods, opting for others that may have nutritional or similar characteristics.
2. Use of medicines or chemicals
This is the second leading cause of change in the color of urine and usually happens due to frequent contact with some chemicals present in various medicines. Some of the drugs or chemicals that can cause black urine are:
- Phenacetin: it is present in many painkillers and when used frequently it leads to the destruction of hemoglobin in the blood, which is eliminated in the urine, causing a very dark color; Levodopa: is a medicine used in Parkinson's treatment that contains L-dopa, which can make the urine very dark; Phenol: this substance normally enters the body through repeated contact with disinfectant or cleaning products, so it is recommended to use gloves when using this type of product; Laxatives: some contain cascara or senna, two substances that when used in excess can make urine very dark; Chloroquine and Primaquine: are remedies used to treat malaria that can cause black urine, as a side effect; Furazolidone, Metronidazole or Nitrofurantoin: they are antibiotics that can change the color of the urine, and can vary between dark red and black; Methyldopa: is a medicine for high blood pressure that releases metabolites in the urine that, when they come in contact with the bleach used in cleaning the toilet, can cause black urine.
In some cases, povidone-iodine, which is a liquid widely used to clean some wounds, when used on very large areas of skin can be absorbed by the body and eliminated in the urine, causing the color black.
What to do: When the problem is caused by the use of these drugs, one should consult the doctor who prescribed them to adapt the dose used or change the medication.
3. Diseases
One of the main health problems that can cause the appearance of black urine is skin cancer, as this disease causes an exaggerated production of melanin, the substance that causes dark skin color. When it is present in high levels, melanin can be eliminated by the body through urine, leaving it dark brown or black.
However, other more rare diseases such as Alcaptonuria, cutaneous Porphyria or Black Water Fever can also cause black urine. In addition, liver problems, such as hepatitis or cirrhosis, kidney infections, or diseases caused by viruses such as Haff's disease, can make urine very dark in color, such as brown or red, and can easily be mistaken for black urine.
What to do: If the black urine happened without any relation to the use of medication or food, it is advisable to consult a general practitioner quickly to identify if there is a disease that is causing the problem, in order to start the appropriate treatment, which varies according to the cause.
