To correctly diagnose a patient with anorexia nervosa, medical history according to DSM-IV or ICD-10 criteria and the physical examination is essential. Furthermore, it is useful for a physician to have knowledge regarding typical alteration in laboratory parameters of anorectic patients to realize diagnostical hints. Typical laboratory changes, although not exclusively seen in anorexia nervosa, include hyponatremia, hypokalemia, hypochloremia, liver enzyme elevation, and low red and white blood cell count. The hormones leptin, neuropeptide Y (NPY), triiodothyronine (T3), follicle-stimulating hormone (FSH), luteinizing hormone (LH) and oestrogen are usually below the normal range, whereas ghrelin, pancreatic polypeptide (PP), tumor necrosis factor-alpha (TNF-alpha) and cortisol levels are reported to be typically elevated.