Evaluation to rule out other causes of shock, diarrhea, etc.
24 hour urinary HIAA (5-hydroxyindoleacetic acid)
Echocardiography
Imaging to locate the tumor, if not known
Carcinoid syndrome
Allergic reaction/urticaria
Hemochromatosis
Anaphylaxis
Amyloidosis
Angioedema
Celiac disease
Anxiety attack