Final answer:
A patient with symptoms of ringing in ears, abdominal pain, and mild metabolic acidosis may have overdosed on a substance like aspirin, which leads to acidosis due to the acidity of its metabolite, sulfasalicylic acid.
Step-by-step explanation:
The patient presenting with symptoms of ringing in ears, abdominal pain, and mild metabolic acidosis could be suffering from an overdose of a substance that causes acidosis. One such substance is aspirin, whose active metabolite sulfasalicylic acid can cause acidosis through its acidity upon overdose. Other possible substances that can induce metabolic acidosis when overdosed include uremia due to the retention of urea and uric acid, diabetic ketoacidosis from an excess of ketones in the blood, or a decrease in hydrogen ion excretion which hinders bicarbonate conservation.