Laboratory Studies to Rule Out Organic Causes Complete blood cell (CBC) count Thyroid-stimulating hormone (TSH) Vitamin B-12 Rapid plasma reagin (RPR) HIV test Electrolytes, including calcium, phosphate, and magnesium levels Blood urea nitrogen (BUN) and creatinine Liver function tests (LFTs) Blood alcohol level Blood and urine toxicology screen Arterial blood gas (ABG) Dexamethasone suppression test (Cushing disease, but also positive in depression) Cosyntropin (ACTH) stimulation test (Addison disease)