What medications or foods can cause black tarry stool?

Understanding “Black and Tarry” Stools (Melena)
Black, tarry stools—known medically as melena—can be alarming. In many cases, they result from harmless causes such as certain foods or over-the-counter remedies. However, melena can also signal bleeding in the upper gastrointestinal (GI) tract. This guide outlines common medications and foods that may turn your stool black or tar-like, helps you distinguish benign causes from those needing prompt medical attention, and suggests next steps if you’re concerned.

Why Stool Turns Black and Tarry

Stool color normally reflects what you eat plus the digestive processes in your gut. When blood enters the stomach or small intestine, digestive enzymes break it down, producing a dark, sticky, “tar-like” stool. But various non-bleeding substances can mimic this appearance by staining stool a dark color.

Medications That Can Cause Dark or Tarry Stool

• Iron supplements
– Ferrous sulfate, ferrous gluconate, ferrous fumarate
– Commonly taken to treat or prevent iron-deficiency anemia
– Often produce stools that are dark green, black, or tarry
• Bismuth-containing products
– Pepto-Bismol (bismuth subsalicylate), Kaopectate
– Bismuth combines with small amounts of sulfur in saliva and gastric juices, forming bismuth sulfide (black pigment)
– Stools may appear uniformly black but are usually non-sticky
• Activated charcoal
– Used in emergency treatment of certain types of poisoning
– Binds toxins in the gut but will also blacken stool
• Barium sulfate
– Given by mouth or enema for imaging tests (barium swallow, upper GI series)
– Renders stool white to chalky immediately after the test, then often darkens as remnants pass
• Medications containing heavy metals or dyes
– Some compounds with lead, bismuth, or indigo dyes (rare in modern pharmaceuticals)
– Can impart a black or bluish hue to stool

Foods and Beverages That May Darken Stool

• Black licorice and dark candies
– Artificial coloring and licorice root extract can stain stool dark
• Blueberries, blackberries, and grape juice
– Deep-colored berries and juices may leave a dark residue
• Dark chocolate and cocoa
– High concentrations of cocoa may darken stool slightly
• Beets (rarely)
– More likely to cause red or pink stool (“beeturia”) but may appear dark in small amounts
• Iron-rich foods
– Spinach, kale, prunes, blackstrap molasses
– Can darken stool if consumed in large quantities
• Artificial food dyes (E151, E180)
– Found in some processed foods, candies, and baked goods

Distinguishing Benign Staining from True Melena

It’s important to tell harmless darkening apart from melena caused by bleeding:

1. Texture and Consistency
   – Benign discoloration: stool color changes but remains formed and soft.
   – True melena: stool is sticky, tar-like, foul-smelling, often with an oily sheen.

2. Timing and Pattern
   – Benign causes: color change usually follows consumption of a specific food or medication and resolves within a day or two of stopping it.
   – True melena: persists or worsens, may be accompanied by other symptoms.

3. Additional Symptoms
   – Check for fever, abdominal pain, lightheadedness, weakness, or signs of anemia (paleness, rapid heartbeat).
   – Bleeding may also produce coffee-ground vomitus or bright red blood in vomit or stool (hematemesis or hematochezia).

Medications That May Cause GI Bleeding (and Melena)

Some drugs don’t directly stain stool but can cause upper GI bleeding, leading to true melena:
• Non-steroidal anti-inflammatory drugs (NSAIDs)
– Ibuprofen, naproxen, aspirin
– Can irritate the stomach lining, increasing risk of ulcers and bleeding
• Blood thinners (anticoagulants)
– Warfarin, heparin, direct oral anticoagulants (e.g., apixaban, rivaroxaban)
– Heighten bleeding risk in presence of stomach ulcers or lesions
• Corticosteroids (when combined with NSAIDs)
– Prednisone, dexamethasone
– May exacerbate ulcer formation when used long-term alongside NSAIDs

If you’re taking these and notice black, tar-like stools, assume it could be melena and seek medical advice promptly.

What to Do If You Notice Black, Tarry Stool

1. Review recent diet and medications
   – Ask: Did I take iron, Pepto-Bismol, activated charcoal, or eat a lot of dark berries or licorice?
   – If yes, hold the suspect item and watch for 24–48 hours.
2. Monitor associated symptoms
   – Dizziness, faintness, rapid heartbeat → could signal significant blood loss
   – Abdominal pain, vomiting, fever → might indicate ulcer or infection
3. Consider a free, online symptom check, using the doctor approved Ubie Symptom Checker
   – Ubie’s tool can help you understand possible causes based on your full symptom profile.
   – Click here: free, online symptom check, using the doctor approved Ubie Symptom Checker
4. Keep track of changes
   – Note stool color, frequency, and any new symptoms
   – Share this information with your healthcare provider

When to Seek Immediate Medical Attention

Black, tarry stools can sometimes signal life-threatening conditions. Seek emergency care or call your doctor right away if you experience:
• Profuse, ongoing black stools or bright red blood in stool
• Dizziness, fainting, or rapid heart rate
• Severe abdominal pain or cramping
• Vomiting blood or coffee-ground material
• Signs of shock (sweating, paleness, confusion)

Talking to Your Doctor

Even if you suspect a harmless cause, it’s wise to discuss any unexpected change in bowel habits. When you speak to your doctor, be prepared to share:
• A list of all medications, vitamins, and supplements you take
• Details on recent meals, especially dark-colored foods or drinks
• Onset, duration, and appearance of the stool change
• Any other symptoms (pain, dizziness, fatigue)

Your doctor may recommend simple stool tests, blood work, or imaging studies. In some cases, an upper endoscopy (EGD) is needed to directly view the lining of your esophagus, stomach, and small intestine.

Key Takeaways

• Black and tarry stools can be caused by harmless substances like iron supplements, bismuth products, activated charcoal, or certain foods and dyes.
• True melena—sticky, foul-smelling, tarry stool—often signals upper GI bleeding and warrants prompt evaluation.
• Review recent dietary changes or over-the-counter remedies first; if discoloration persists or is accompanied by worrisome symptoms, seek medical care.
• Consider a free, online symptom check, using the doctor approved Ubie Symptom Checker, to help clarify possible causes.
• Always speak to a doctor about anything that could be life-threatening or serious.

If you have any concerns about black, tarry stool or other GI symptoms, don’t hesitate—speak to a doctor today.