Lead and other heavy metals are classified as which in urinalysis?

• A. Common toxins
• B. Proteins
• C. Enzymes
• D. Hormones

Answer: (A)

Lead and other heavy metals are exogenous substances that the body eliminates through urine because they are toxic to cells. In urinalysis, substances are categorized based on their nature: normal body-derived constituents like proteins, enzymes, and hormones, or non-native toxicants. Heavy metals do not represent normal urinary components; their presence indicates exposure to toxins and potential harm, so they’re classified as toxins (often referred to in teaching materials as common toxins). This distinction helps clinicians differentiate routine urine findings from indicators of environmental or occupational exposure to harmful metals.