Dehydration: This is often the most common reason for dark or tea-colored urine, as it concentrates the urine, making it appear darker than usual. Prolonged dehydration over a month could easily lead to this symptom.

Liver Disease (e.g., Hepatitis, Cirrhosis): Liver conditions can lead to changes in urine color due to the buildup of bilirubin, a byproduct of the liver's processing of old red blood cells. Tea-colored urine can be a sign of bilirubin in the urine.
Kidney Disease: Certain kidney diseases can cause changes in urine color, including tea-colored urine, due to the kidney's inability to properly filter waste and excess fluids.
Urinary Tract Infection (UTI): While more commonly associated with symptoms like burning during urination and frequent urination, some UTIs can cause changes in urine color.

Hemolytic Anemia: This condition involves the breakdown of red blood cells faster than they can be made. It can lead to the release of bilirubin into the bloodstream, which is then excreted into the urine, causing it to appear tea-colored. Missing this diagnosis could lead to severe anemia and other complications.
Malignancy (e.g., Bladder, Kidney, or Liver Cancer): Although less common, certain cancers can cause changes in urine color, including tea-colored urine, due to the presence of blood or other substances in the urine.

Alkaptonuria: A rare genetic disorder that affects the body's ability to break down certain amino acids, leading to the accumulation of homogentisic acid in the body. This can cause urine to turn dark or tea-colored upon standing.
Porphyrias: A group of rare disorders that can lead to the accumulation of porphyrins in the body, which can cause urine to appear dark or tea-colored.
Melanuria: A condition where melanin is present in the urine, which can cause it to appear dark or tea-colored. This is extremely rare and usually associated with melanoma.