Black Stools and Vomiting Blood: Recognising Upper Gastrointestinal Bleeding
A community pharmacy triage guide to recognising upper gastrointestinal bleeding, distinguishing melaena from iron-induced dark stools, and identifying who needs 999.
Why this matters
Upper gastrointestinal (GI) bleeding is bleeding from anywhere between the oesophagus and the duodenum. It ranges from a slow ooze from a peptic ulcer to catastrophic haemorrhage from oesophageal varices in a patient with liver disease. Community pharmacists encounter it regularly, often without realising: the person asking for antacids because of indigestion and dark stools, the warfarin patient whose stools have changed colour, or the regular ibuprofen user who mentions feeling dizzy when standing up.
The critical pharmacy skill is not treatment: it is recognition and referral speed. The two presentations that matter most are melaena (typically jet black, tarry, and sticky stools from digested blood, often with a characteristic offensive odour) and haematemesis (vomiting bright red blood or material resembling coffee grounds). Both require urgent medical assessment. The pharmacist's most common trap is reassuring a patient on iron tablets that black stools are simply a side effect, when the stools are in fact melaena. The distinction is made on stool character, consistency, associated symptoms, medication history, and context rather than colour alone.
Several medicines dispensed every day in community pharmacy substantially increase the risk of upper GI bleeding: non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen, and diclofenac; antiplatelet medicines including low-dose and standard-dose aspirin, clopidogrel, and ticagrelor; oral anticoagulants including warfarin, apixaban, rivaroxaban, edoxaban, and dabigatran; corticosteroids (particularly when combined with NSAIDs); and selective serotonin reuptake inhibitors (SSRIs), particularly when combined with NSAIDs. Patients receiving both anticoagulants and antiplatelet medicines are at particularly high risk of GI bleeding.
Red flags vs more likely benign
| Feature | More likely benign | Red flag ⚠ |
|---|---|---|
| Stool appearance and character | Dark stools shortly after starting iron tablets or bismuth (Pepto-Bismol): not sticky, not tarry, no offensive odour | Jet black, tarry, sticky stools, often with a characteristic offensive odour (melaena): digested blood from the upper GI tract. This is not an iron tablet side effect. |
| Vomiting | Nausea or vomiting without any blood, bile-coloured | Bright red blood vomited, or vomit that looks like coffee grounds (haematemesis): both indicate active or recent upper GI bleeding. Call 999. |
| Dizziness and postural symptoms | Mild, brief, situational dizziness unrelated to standing | Dizziness specifically on standing up, near-fainting, or actual fainting: suggests significant blood loss with haemodynamic compromise |
| Abdominal pain | Mild, intermittent upper abdominal discomfort, typical indigestion pattern | Severe, persistent upper abdominal pain, or pain that is tender to touch: may indicate perforation alongside bleeding |
| General appearance | Alert, comfortable, normal skin colour | Pale, cold or clammy skin, marked fatigue or weakness: signs of significant blood loss requiring urgent assessment |
| Medication history | No relevant medicines; isolated dark stool with clear cause (iron started this week) | Current or recent NSAIDs, aspirin, clopidogrel, ticagrelor, anticoagulants, corticosteroids, or SSRIs: all increase bleeding risk. New dark stools or GI symptoms in these patients warrant same-day assessment. |
| Background history | No relevant GI history, liver disease, or previous bleeding | Known peptic ulcer disease, liver disease, heavy alcohol use, or previous upper GI bleed: all significantly increase the risk of serious haemorrhage |
Think Upper GI Bleeding if Your Patient Says...
These phrases should immediately raise concern. The melaena description is the most important: patients will often struggle to describe it, but they know it is different.
- "My stools have been really dark, almost black, and they smell awful."
- "I was sick this morning and there was blood in it, or it looked like coffee grounds."
- "I feel really dizzy when I stand up."
- "I am on warfarin and my stools have turned black."
- "I take ibuprofen every day for my back and I have started getting indigestion and dark stools."
- "The stools are sticky and very dark, not like when I took iron before."
A patient who says their black stools smell different, feel different, or have appeared alongside dizziness or vomiting needs urgent assessment, not reassurance. If in doubt about whether black stools are melaena or medication-related, refer rather than wait.
🛑 TARRY: A Quick Assessment Framework
Use this prompt when a patient reports black stools, dark stools, or vomiting with blood.
Melaena is jet black, sticky like tar, and often has an offensive odour. Iron and bismuth cause dark stools without this character. Ask: is it sticky? Does it smell different from normal?
NSAIDs, aspirin, clopidogrel, ticagrelor, warfarin, apixaban, rivaroxaban, edoxaban, and dabigatran all increase GI bleeding risk. Any possible melaena in these patients needs same-day assessment.
Haematemesis in any form (bright red or coffee-ground) is a 999 situation. There is no safe watchful waiting option for vomiting blood.
Postural dizziness or near-syncope means significant blood loss has already occurred. Call 999 without delay.
Upper GI bleeding can worsen rapidly. When any of the above are present, pharmacy is not the right setting. Refer to 999 or same-day urgent care and do not offer antacids as a holding measure.
Common Causes and High-Risk Groups
Knowing the causes helps the pharmacist ask the right questions and identify who is at greater risk of serious haemorrhage.
- Peptic ulcer disease: the most common cause of upper GI bleeding, caused by Helicobacter pylori infection or NSAID use. Patients often have a background of indigestion, night pain, or previous ulcer diagnosis.
- Oesophageal varices: dilated veins in the oesophagus caused by portal hypertension, usually from liver disease or heavy alcohol use. Variceal bleeds can be catastrophic and rapidly fatal.
- Mallory-Weiss tear: a mucosal tear at the junction of the oesophagus and stomach, typically following forceful or prolonged vomiting. Bright red haematemesis after retching is the characteristic presentation.
- Gastric erosions, gastritis, and oesophagitis: common in NSAID users, heavy alcohol users, and those on corticosteroids.
- Gastric or oesophageal cancer: consider alongside upper GI bleeding in any patient with unexplained weight loss, difficulty swallowing, or persistent symptoms despite treatment.
Any patient with known liver disease who develops haematemesis should be assumed to have possible variceal bleeding until assessed in hospital: variceal bleeds can deteriorate extremely rapidly and always require 999. The highest-risk medication combination is an anticoagulant alongside an antiplatelet agent (aspirin, clopidogrel, or ticagrelor). Many patients on long-term NSAIDs, particularly those at increased GI risk, should also receive gastroprotection with a proton pump inhibitor (PPI): if it is not in place, this is a medicines optimisation opportunity as well as a safety concern.
What to do in pharmacy
Key takeaways
- Melaena is jet black, tarry, sticky, and often has an offensive odour: do not reassure a patient that black stools are caused by iron tablets without confirming the stools lack these features.
- Any haematemesis (vomiting blood or coffee-ground material) and any melaena with dizziness, pallor, or fainting requires 999 without delay.
- Patients on anticoagulants, NSAIDs, or aspirin with new dark stools or GI symptoms need same-day medical assessment, not antacids.