Single most likely diagnosis
- Dehydration: This is often the most common cause of dark or black urine, as concentrated urine can appear darker due to the higher concentration of waste products.
Other Likely diagnoses
- Medication side effects: Certain medications, such as metronidazole or rifampicin, can cause urine to turn dark or black.
- Alkaptonuria: A rare genetic disorder that affects the breakdown of certain amino acids, leading to the accumulation of homogentisic acid, which can cause urine to turn black upon standing.
- Melanin or melanogen: In some cases, the presence of melanin or its precursors in the urine can cause it to appear black.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Rhabdomyolysis: A serious condition where muscle tissue breaks down, releasing myoglobin into the bloodstream, which can then be excreted in the urine, causing it to appear dark or black.
- Hemolysis: The breakdown of red blood cells can release hemoglobin into the urine, which can cause it to appear dark or black.
Rare diagnoses
- Porphyria: A group of rare genetic disorders that can cause the accumulation of porphyrins, which can lead to dark or black urine.
- Fungal infections: Certain fungal infections, such as those caused by Aspergillus or Candida, can produce pigments that cause urine to appear black.
- Prolonged exposure to certain chemicals: Exposure to certain chemicals, such as aniline dyes, can cause urine to appear black.