If some one drink drano wouldn't show and his blood or his toxic level?

Caustic ingestion: If someone drinks a corrosive alkali substance, such as drain cleaner, which contains sodium or potassium hydroxide; it will be diagnosed based on information provided in a history, not by a blood test. Symptoms may vary. Patients may complain of pain in the mouth/throat, chest or stomach, or painful/difficult swallowing. They may have vomiting or belly tenderness, if the GI tract has perforated.