1. Acute kidney injury (AKI) can be diagnosed by assessing urine and serum markers such as a urine sodium level greater than 20 or a serum urea/creatinine ratio greater than 40, which indicates pre-renal AKI. 2. Laboratory tests that can help determine the underlying cause of AKI include checking for hypercalcemia, which can indicate multiple myeloma or lymphoma, and measuring CPK to check for rhabdomyolysis. 3. An elevated osmolar gap on lab tests, particularly one over 25, along with an otherwise unexplained high anion gap metabolic acidosis, suggests ethylene glycol or methanol intoxication in a patient suspected of poisoning.