Dehydration: This is a common and straightforward cause of dark urine, especially in adolescents who may not drink enough water throughout the day. Dehydration concentrates the urine, making it appear darker.

Urinary Tract Infection (UTI): UTIs can cause changes in urine color, including darkening, due to the presence of blood, bacteria, or other substances.
Kidney Stones: While less common in adolescents, kidney stones can cause pain and changes in urine color, including darkening due to blood or concentrated urine.
Menstrual Blood in Urine: In adolescent females, menstrual blood can sometimes be mistaken for dark urine, especially if there is heavy menstrual flow or if sanitary products are not used correctly.

Rhabdomyolysis: A serious condition where muscle tissue breaks down, releasing myoglobin into the bloodstream, which can cause dark, tea-colored urine. This condition requires immediate medical attention.
Hemolytic Uremic Syndrome (HUS): A condition characterized by the destruction of red blood cells, which can lead to kidney failure and dark urine. It's crucial to identify and treat HUS promptly.
Acute Kidney Injury (AKI): Any condition that causes a sudden loss of kidney function can lead to changes in urine output and color, including dark urine. Early detection and treatment of AKI are vital.

Alkaptonuria: A rare genetic disorder that affects the breakdown of certain amino acids, leading to dark urine due to the accumulation of homogentisic acid.
Melanuria: A condition where melanin is present in the urine, giving it a dark color. This can be associated with melanoma or other conditions affecting melanin production.
Porphyrias: A group of rare genetic disorders that can affect the production of heme, leading to the accumulation of porphyrins in the urine, which can cause it to appear dark.