The Arsenic 24-Hour Urine Test (or Arsenic 24H) measures total arsenic in your urine over a full day to assess recent exposure, especially when the source is unknown, helping diagnose arsenic poisoning by identifying harmful inorganic vs. benign organic forms. It requires collecting all urine for 24 hours in a special metal-free container, avoiding seafood/supplements beforehand, and the lab analyzes the total amount, often fractionating it to see types of arsenic. High levels (often >100 µg/L) suggest significant exposure, guiding doctors to potential sources like contaminated water, food (seafood), or industrial areas