Large Black Spots In Stool: Common Causes & When To Worry

Our content is not intended nor recommended as a substitute for medical advice by your doctor. Use for informational purposes only.

Quick Insights from the article:

  • In 90% of cases, black spots in stool are due to the food or medications you intake.
  • If you are young in age (less than 40) and a healthy individual, it is not necessary to jump into expecting the worst scenario.
  • However, if the condition is persistent or accompanied by other worrisome symptoms, consult your doctor.
  • The first thing to do if you experience black spots in the stool is to review the food and medications you have taken in the past 48 hours. If you intake one of the below-enlisted foods or medication, there is no need to worry.
  • If you have had no food or medication intake in the past 48 hours to black spots, it is better to consult your doctor.


What makes the black spots in your stool?


Simply, one of the 3 major substances can be the cause of dark spots in your stool:

  • Food.
  • Medications.
  • Blood. (digested blood is black.)

As we mentioned before,  food and medications are the major cause of the black spots or patches in your stool. But the presence of the possibility of blood as the cause of dark stool shouldn’t raise unnecessary anxiety about your health, especially if you don’t have worrisome symptoms or risk factors.

So, we will explain in little detail how to suspect each of the medical conditions that may lead to black stool spots or specks.

Please read them carefully and consult your doctor if you find one or more of the red signs enlisted below.


When to see a doctor when you have black spots in your stool?


Consult your doctor if:

    • Signs of anemia: easy fatigue, palpitation (rapid heartbeats), dizziness or fainting attacks.
    • Any other signs of bleeding: such as attacks of black tarry stools, bright red blood in the stool, vomiting of reddish or blackish clots, coffee ground vomiting.
    • Presence of unusual Gut manifestations: such as epigastric pain, unusual abdominal colics, nausea or vomiting, severe diarrhea or mucus in stool.
    • History suggesting peptic ulcer disease: such as the history of abuse of pain medications (ibuprofen, ketoprofen, Naproxen, …etc), previous history of bleeding from peptic ulcer (vomiting blood or passing tarry stool).
    • Signs suspicious of malignancy: weight loss, fever of unknown origin,  family history of colon cancer, or being older in age.
    • History of use of blood-thinning medications: Aspirin in heart disease, Warfarin, or other anticoagulant drugs.
    • History of Major liver conditions (such as liver cirrhosis, Budd-Chiari syndrome).
    • Signs of impaired blood coagulation: such as the presence of reddish-blue skin patches (ecchymosis) or bright red skin spots (petechiae).
    • Black spots in stools that cannot be explained by food or medications.


1- Foods causing black spots in the stool.


The most common cause of black spots in the stool is black food materials. This food material may be: [source]

black stool spots

  • Iron in iron-containing foods:
    • Red meat, 
    • Spinach,
    • beets, 
    • kidney beans, 
    • molasses, 
    • and oysters.
  • Black-colored foods & fruits 
    • Blueberries.
    • Blackberries.
    • Plums.
    • Black beans.
    • Figs.
    • Cherries.
    • Spices such as black pepper.
    • Bananas.
    • Dark puddings
    • Artificial food coloring: such as
      • black licorice.
      • Chocolate puddings.
    • Undigested seeds: such as: 
      • Strawberry seeds.
      • Sesame seeds.
      • Guava seeds.
    • Green leafy vegetables: once digested, they turn dark green or black.
    • Tomatoes and tomato products.
    • Red wine.
    • Raw or undercooked meat: besides containing iron, it also contains some blood inside the meat fibers.


How to deal if you think food is the cause of black spots in stool?

If you have a history of eating one of the above offending foods (especially if you consumed large amounts). You have to follow up on the condition:

  • Cut the offending food and wait for at least 48 hours.
  • Follow up on your black spots in the stool after 48 hours have passed.
  • If food or medications can’t explain the black spots in the stool, ask your doctor about the condition.


2- Medications causing black stool spots.


Medications can cause black or dark spots in stools by one of two mechanisms: (source)

  • Medications that are dark-colored: are common; no need to worry.
  • Medications that cause bleeding inside your gut: many drugs can affect the lining of your stomach or duodenum causing ulcers. Other medications can cause blood thinning and lead to painless bleeding inside your gut.


Medications that are dark-colored: 


1– Iron-containing supplements.

 Iron deficiency anemia medications are a common example. Another common source is general tonic supplements that contain low doses of iron.

2- antacid medications containing Bismuth subsalicylate (Pepto-Bismol ®)

The Bismuth containing antacid is famous for causing dark or black stools and also dark coating of the tongue. If you are using bismuth, consult your doctor about the black spots in your stool. ( as you already may have stomach problems).

If you are taking iron and bismuth, there is no need to worry about them; restricting these drugs can decrease black spots in your stool.

MORE: Pepto Bismol (Bismuth Subsalicylates) OTC: Review & Drug Profile.

3- Blood as a cause of dark spots in your stool: 


Usually, bleeding inside your stomach, small intestine, or colon results in a black or tarry stool. Dark spots are unusual findings. And the presence of only dark spots may denote intermittent bleeding of small amounts of blood. 

Overview of the causes of Gastro-intestinal bleeding:

  • Medications.
  • Peptic ulcer (in stomach or duodenum).
  • Malformed vessels inside the wall of your stomach or intestine.
  • Mallory-Weiss syndrome: minimal bleeding from the esophagus with severe vomiting.
  • A mass inside your stomach, intestine, or colon (Benign as a polyp or cancerous as colon cancer).
  • Generalized bleeding diseases such as low blood platelets and hemophilia.
  • Some parasitic infections, such as Ascaris.
  • Others (see below). 


A- Medications that may cause Gut bleeding (consult your doctor immediately)


Gut bleeding usually leads to tarry blackish stool and not Black spots (rare)

With this type of medication, it leads to

    • black or tarry stool (melena): gut bleeding usually presents with black “tarry” stool. That is usually blackish, liquid, and smells like fish or rotten meat. This is a medical emergency; seek medical assistance as soon as possible.
    • Bright red blood in the stool.
    • Vomiting of blood. 
    • OR less commonly (only if bleeding is minimal) black spots in your stool.

If you have a history of using one of the below drugs, consult your doctor about black spots in your stool.

1- Non-steroidal anti-inflammatory drugs, such as [Ref]

  • Aspirin.
  • Diclofenac
  • Ibuprofen. (Advil ®)
  • Indomethacin (Indocin ®)
  • Ketorolac.
  • Naproxen.

2- Anti-coagulants and antiplatelet drugs: drugs used with certain diseases such as atrial fibrillation, deep venous thrombosis or pulmonary embolism. They include:

  • Warfarin (Coumadin ®)
  • Direct oral anticoagulants.
  • Injection anti-coagulants, such as unfractionated heparin and low molecular weight heparins.
  • Clopidogrel (Plavix ®)


B- Peptic Ulcer disease:


Peptic ulcer disease refers to ulcers occurring in your stomach or duodenum. The most common causes of peptic ulcers are H. Pylori infection and medications such as Non-Steroidal Anti-inflammatory Drugs (mentioned above). 

Stomach and duodenal ulcers are the most common cause of Upper GIT bleeding [Ref]

It is common for peptic ulcers to cause more severe bleeding in the form of black or tarry stool. Minimal or recurrent peptic ulcer bleeding may cause black spots in your stool.

Suspect peptic ulcer as a cause of black spots in your stool if:

  • Stomach pain in the upper part of your abdomen.
  • The pain is burning or discomfort that is related to food.
  • Dyspepsia, Heartburn, nausea, or vomiting may occur.
  • Approximately 70% of Peptic ulcers have NO symptoms at all, so if you have a history of peptic ulcer or using pain medications (NSAIDs), please consult your doctor.


C- Other causes of bleeding from your upper gut tract (Esophagus, stomach, duodenum, and upper part of the small intestine).


causes of black stool, melena

(Data Reference)

Many other causes of bleeding occur but are relatively uncommon, such as:

  • Bleeding from oesophageal or gastric varices: dilated vessels inside the wall of the esophagus or stomach as a result of liver problems (liver cirrhosis, Budd-Chiari syndrome). 
  • Mallory-Weiss syndrome: a tear in the inner lining of the esophagus due to forceful, repeated vomiting.
  • Vascular malformations: abnormal vessels bleed anywhere inside your digestive system.
  • Any gastric masses [benign and malignant tumors: any benign or malignant tumors can lead to bleeding.


D- Bleeding from your colon or small intestine:


Many causes can lead to bleeding inside your colon. But usually, this causes blackish or reddish blood in the stool. Only Minor bleeding may cause dark red or blackish spots in your stool.

Examples include:

    • Diverticular disease: a rare condition where there are multiple sacs in the wall of your colon. The sacs can become inflamed and cause minute bleeding, which can be reddish or blackish spots in your stool. The condition is usually associated with abdominal pain and maybe diarrhea. It is diagnosed by colonoscopy.
    • Inflammatory bowel disease: bloody diarrhea and mucus with abdominal pain, fever, or weight loss. IBD is a Multi-symptomatic disease, unlikely to present only as blackish spots in stool.
    • Bleeding from colon polyp.
    • Mesenteric vascular occlusion: Unlikely because the presentation is severe with intense abdominal pain, distension, and vomiting.


E- Benign or malignant colon tumors (cancer).


Unfortunately, colon cancer may be present as dark or bright blood in the stool without abdominal pain. But usually a bright red or tarry black stool and very rarely as black spots in stool.

Suspect if: (risk factors)

  • If you are older in age (above 40).
  • Unexplained fever or weight loss.
  • Attacks of bright red or black tarry stools [not only black spots].
  • Family history of colon cancer.

No need to worry if you have just one risk factor, and only consult your doctor about colon cancer if:

  • Having more than a risk factor.
  • Black spots didn’t go away after cutting offending foods or medications.

We discussed in-depth the signs and risk factors of colon cancer here.

Learn more here.

MORE: 5 Causes of Painless Bright Red Blood in Stool & When to Worry.


E- Parasitic infections: 


Some parasitic infections may cause minute bleeding inside your intestine or colon. Which presents as black spots in your stool. [source]

Common parasites causing such conditions are Ascaris and tape-worms. Parasitic infection usually presents as abdominal pain, distension, anal itching, and diarrhea. 

You may also see the offending parasite in your stool. Consult your doctor if you suspect that parasitic infestations cause dark spots in the stool.


F- Impaired blood coagulation:


Impaired blood coagulation can lead to serious bleeding. It occurs due to:

  • Blood diseases: most commonly idiopathic thrombocytopenic purpura (ITP).
  • Medications (anticoagulants): as we mentioned before.

Suspect impaired blood coagulation if:

  • Having reddish-blue patches under your skin (ecchymosis)
  • Have small reddish spots under your skin(petechiae).
  • Bleeding tendency: bleeding gums, nose, excessive menstruation, vomiting of blood, or bleeding under your eye whites).
  • History of taking the anticoagulant medication.

Bleeding due to impaired blood coagulation occurs at multiple sites simultaneously. And the skin is usually involved. It is unlikely to cause isolated black spots in your stool.

Learn more about bleeding disorders.

MORE: Dark Green Poop: 6 Causes Explained.