CBC
Chemistries
BUN may be elevated if bleeding occurs from site high in GI tract
Coags
LFTs
Type and screen
Consider:
ECG (if concern for silent ischemia in patients likely to have CAD)
Fibrinogen
CTA
Requires brisk bleeding rate (0.5 cc/min) for detection[citation needed]
Tagged red blood cell scan (not typically an emergency study)
BUN may be elevated if bleeding occurs from site high in GI tract
ECG (if concern for silent ischemia in patients likely to have CAD)
Fibrinogen
CTA
Requires brisk bleeding rate (0.5 cc/min) for detection[citation needed]
Tagged red blood cell scan (not typically an emergency study)
Requires brisk bleeding rate (0.5 cc/min) for detection[citation needed]
Consider:
Anoscopy if source of bleeding cannot be identified on external exam
Proctoscopy (22cm from anal verge)
Sigmoidoscopy (60cm from anal verge)
Anoscopy if source of bleeding cannot be identified on external exam
Proctoscopy (22cm from anal verge)
Sigmoidoscopy (60cm from anal verge)
Red meat
Red jello
Fruit and vegetables
Melon, broccoli, radish, beets
Iron (causes GI bleed by irritation)
Melon, broccoli, radish, beets
Lower gastrointestinal bleeding
Upper GI Bleeding
Gastrointestinal bleeding 
Diverticular disease
Colitis
Diverticulosis
Leaking G-tube
Diverticulitis