Most arsenic exposures are chronic, without obvious symptoms or signs, and so medical management shifts to prevention, mitigation, and risk assessment. If, despite avoidance of arsenic (primarily in water and food), there is remaining concern or clinical suspicion for potential ongoing arsenic exposure; a quantitative timed urine specimen (8 or 12 hours in children 24 hours in adults; a first morning “spot” urine, along with a urine creatinine to correct for concentration, is less accurate). An acid-washed container should be used to avoid sample contamination. If the laboratory reports total arsenic, it should be “speciated” or fractionated to distinguish between the toxic inorganic species (if present) as well as the organic species (currently considered non-toxic) typically found in seafood. Consultation with laboratory staff is recommended before ordering the test. For more information, visit Agency for Toxic Substances and Disease Registry (ATSDR) Arsenic Toxicity website.