What can cause urine to appear dark yellow or amber?

When urine appears dark yellow or amber, it is primarily an indication of increased concentration of the urine, most commonly due to dehydration. When the body is dehydrated, there is less water available to dilute the waste products that are excreted, leading to a more concentrated urine that reflects its higher solute content. This concentration can cause the urine to take on a darker hue, ranging from deeper shades of yellow to amber.

In contrast, excessive water intake typically leads to diluted urine, making it appear more pale or clear. The ingestion of certain foods and a high-protein diet can also influence urine color, but these effects are generally more variable and not as directly linked to dark coloration as dehydration is. For instance, certain foods like beets or blackberries can lead to red or pink urine, while a protein-rich diet might result in darker urine but typically this would not be uniformly amber as dehydration would cause. Thus, the most direct and common cause for dark yellow or amber urine is indeed dehydration.