Black urine is typically caused by the ingestion of foods with natural or artificial coloring, such as rhubarb, fava beans, plums, and ice cream, but can also be caused by medications like levodopa or phenol.

Black urine can also be caused by more serious health conditions like Haff disease, liver problems, kidney disease, rhabdomyolysis, or skin cancer that need to be identified and treated.

It is important to consult a nephrologist or urologist for black urine lasting more than 2 days or accompanied by symptoms like severe pain, joint stiffness, or unexplained weight loss. Tests can be done to help identify a cause and arrange for the best treatment.

gloved hand holding a vial of dark urine

Main causes

The main causes of black urine are:

1. Eating certain foods

Certain foods may cause black urine due to natural or artificial colors, which is not cause for concern. This include foods like rhubarb, fava beans, and aloe vera.

Excess consumption of foods high in sorbitol, like apples, pears, peaches, and plums, as well as sugar-free foods like gum, ice cream, or candies, can also turn the urine black. Large quantities of sorbitol also cause stomachache, cramps, and diarrhea.

The use of copper pots for cooking may also cause black urine in some people, especially in individuals who are unable to metabolize copper and end up eliminating it in large quantities in the urine, turning the urine black.

What to do: People who experience black urine after consuming meals high in the foods listed above should avoid these foods and opt for other foods with similar nutritional benefits.

2. Taking certain medications

Regular use of certain medications may also cause black urine. This typically happens as the result of frequent contact with certain chemicals present in these medications. Some medications and chemicals that can cause black urine include:

Levodopa: A medication used to treat Parkinson's disease that contains L-DOPA, which can make the urine very dark;
Phenol: A substance that typically enters the body through repeated contact with disinfectants or cleaning products, making it important to wear gloves when handling these products;
Laxatives: Some laxatives contain cascara sagrada or senna, two substances that when used in excess can cause very dark urine;
Chloroquine and primaquine: Medications used to treat malaria that may cause black urine as a side effect;
Furazolidone, metronidazole, or nitrofurantoin: Antibiotics that can change the color of the urine to a dark red or black color;
Methyldopa: A blood pressure medication that releases metabolites in the urine that can cause the urine to appear black when they come into contact with bleach used to clean the toilet.

When used over large areas of the skin, povidone-iodine (which is commonly used to clean wounds) can be absorbed by the skin and eliminated through the urine, causing the urine to turn black in color.

What to do: It is recommended to consult your prescribing provider if you are experiencing black urine caused by medications. Treatment may include switching medications, changing the dose, or suspending use of the medication.

3. Haff disease

Black urine is one of the main symptoms of Haff disease, which is a rare disease caused by a thermostable biological toxin that can be found in certain freshwater fish and crustaceans.

The presence of this toxin in the body can cause destruction of muscle cells, resulting in severe pain, muscle stiffness, and numbness in addition to dark urine related to kidney damage.

What to do: Symptoms of Haff disease develop a few hours after coming into contact with the toxin. People experiencing symptoms of Haff disease after consuming freshwater fish or crustaceans should go to the nearest hospital for treatment, which consists of hydration, analgesics, and diuretics to help eliminate the toxin from the body.

4. Rhabdomyolysis

Rhabdomyolysis is a serious condition involving destruction of the muscle fibers that can happen as the result of intense and prolonged physical exercise, poisoning from drinks or medications, or prolonged immobilization.

Symptoms of rhabdomyolysis include weakness, dark urine, nausea and vomiting, joint pain, and general malaise, which are caused by an accumulation of the contents of muscle cells due to the destruction of muscle fibers.

What to do: People with suspected rhabdomyolysis need to be seen right away at the hospital for testing to confirm the diagnosis and determine the severity of the condition. In some cases, it may be necessary for the individual to stay at the hospital to receive fluids and medications through an IV as well as monitoring to prevent complications.

5. Liver problems

Black urine can also be a sign of certain liver problems, such as cirrhosis and hepatitis, due to alterations in liver function that interfere with the proper breakdown of bilirubin so it can be eliminated in the urine. This accumulation of bilirubin leads to dark-colored urine.

What to do: It is important to consult your primary care provider or a hepatologist for an evaluation to help identify any liver conditions that could be causing black urine. Based on the cause, treatment may involve medications and dietary changes.

6. Kidney disease

Kidney damage related to infection or illness can also cause black urine due to problems in filtration and absorption that result in darker, more concentrated urine.

What to do: A primary care provider should evaluate for symptoms of kidney disease and may need to place a referral to a urologist or nephrologist to help identify a cause and arrange for the best treatment. Treatment will vary based on the cause and may involve antibiotics (in the case of infection), diuretics, and antihypertensives, as well as dietary changes.

7. Alkaptonuria

Alkaptonuria, also called ochronosis, is a rare genetic disease that can also cause black urine.

This is due to the accumulation of a substance called homogentisic acid caused by the lack of a certain enzyme in the body.

Other symptoms of alkaptonuria are dark spots in the white part of the eye (sclera) and around the ears and stiffness of the cartilage.

What to do: There is no cure for alkaptonuria, however treatment of the condition can help manage symptoms and improve quality of life. Treatment may include anti-inflammatories and analgesics, physical therapy, and dietary changes, including increasing consumption of vitamin C foods.

8. Skin cancer

Black urine can also be a sign of skin cancer due to the excess production of melanin, the substance responsible for pigmentation. Melanin that is eliminated through the urine oxidizes when it comes into contact with the air, making the urine appear darker.

What to do: In the case of skin cancer, it is necessary to follow a treatment plan recommended by an oncologist or dermatologist, which may involve surgery to remove the cancerous lesion followed by sessions of chemotherapy and radiation.