Black Stool - Should I Be Worried?

Black stool ! You notice this when you go to the bathroom; should you worry? Is this a medical emergency or just something you have eaten? You are probably wondering " what does black stool mean ?" Find out here when you should take action and what the possible causes are.

Melena is the medical term used by your doctor to describe this type of stool when it is caused by bleeding from high up in the intestinal tract.

False melena is dark stool caused by something else.

In this section of the website we are going to look at different stool types and when you should be concerned. We are starting with black stool. This can have different causes but if it is dark black and has a sticky, tarry, loose consistency and is like diarrhea it will probably indicate that you are bleeding from somewhere in the intestinal tract.

Normally the bleeding site will be in the esophagus (the food pipe), the stomach or the duodenum (the first part of the small intestine attached to the stomach).

As the stools pass along the intestinal tract enzymes start to digest the blood and it turns from red to black.

Sometimes bleeding from lower down in the intestines can cause melena if the transit time of the stools is very slow.

If you experience this type of bowel movement you should see a doctor urgently. Sometimes melena can indicate a slow bleed but if it is severe or you have more than one episode it could indicate a large hemorrhage, especially if you feel faint and have a rapid heartbeat. If this happens to you, then go to the hospital immediately.

Melena Case Study

Once I was working on a surgical ward when a frail elderly lady was admitted suffering from epigastric pain (central pain below the breast bone and above the belly button). Let’s call her Lily. She was pale and feeling faint. Lily’s daughter had called the family doctor to see her mother as she was concerned about her condition and he had arranged for her to be admitted for tests.

As we were waiting for the ward doctor to arrive and examine her she suddenly experienced a large black melenic bowel movement. Her stools were just like a large pool of tar in the bed.

We knew that this had turned from a routine admission, into a medical emergency.  Oxygen and a blood transfusion were started immediately (with O negative blood, the universal donor) and she was rushed to theater for surgery where they discovered that Lily had a perforated duodenal ulcer.

Lily was fortunate that she was in the right place, at the right time and her life was saved.

Black Stool Causes

There are many different things that can cause black stool. Some of them need further investigation as they are causing bleeding but this color stool can be the result of ingesting certain foods and medications. In these cases it is nothing to worry about.

Causes of Bleeding That Can Lead to Black Stools

  • Bleeding ulcer in the stomach or the duodenum
  • Tear in the esophagus due to major vomiting (Mallory-Weiss tear)
  • Widened veins of the stomach or esophagus (varices)
  • Inflammation of the stomach or esophagus
  • Crohn’s Disease
  • Overdose of blood thinning drugs like Coumadin (Warfarin)
  • Use of certain medicines like aspirin, steroids and chemotherapy drugs
  • Tumors of the upper intestinal tract
  • Foreign body causing trauma
  • Trauma caused externally via a blow for example
  • Bleeding from an abnormal blood vessel

False Melena

There are some things which when ingested can lead to black stool but this type of false or pseudo melena is not caused by dangerous bleeding and is not usually anything to worry about.

If you have black feces when you open your bowels, before you begin to panic, first consider, could it be one of these things which can make a person's stool change to this color?

  • Liquorice
  • Blueberries
  • Iron tablets
  • Pepto-bismol
  • Blood sausage
  • Nose bleed (the blood can be swallowed)
  • Squid ink
  • Lead poisoning
  • Stout beer like Guinness
Black Stool - Blueberries

Are My Stools Really Black?

Sometimes it can be difficult to tell if you have black stools or if they are dark green because in the toilet bowl these two colors can look very similar.

A good way to tell the difference is to open your bowels onto some tissue and smear some onto white paper. Shine a light onto the paper and you will easily be able to tell if you have black stool or dark green.

For more information about green stools see here.


Black stools or melena can lead to hypovolemic shock. This is when the volume of blood in the circulation falls by one fifth or more. It is a medical emergency and if not treated promptly can lead to death. The symptoms are:

  • Cool clammy skin
  • Pale skin
  • Rapid breathing
  • Rapid weak pulse
  • Feeling faint or dizzy
  • Weakness
  • Little or no urine output
  • Confusion and or agitation
  • Unconsciousness

If you suspect shock then lie the affected person flat, keep them warm and raise their feet (unless they have a spinal or head injury). Give nothing by mouth. Seek emergency medical help immediately.

If you go to the bathroom and are shocked to see black stool do not panic. First think about anything you have eaten or swallowed which may have resulted in black stools. If however, you have tell tale black tarry stools which are like the tar that they use to repair the roads you should immediately seek medical attention.

If you have other types of diarrhea then please look at causes of diarrhea.

For more information about black poop and different types of stool please see the related pages below.

If you have black tarry stools like Lily in the case study then please see more information here.

Black Poop Causes

Black poop can be a sign of bleeding from the upper intestinal tract but it is commonly caused by everyday foodstuffs. Read more here about the hoaxers which can make you worry.

Go to Black Poop Causes

Red Poop - Should I Worry?

You could be bleeding but it is far more common for red poop to be caused by something you have eaten. Read more about this worrying sign.

Go to Red Poop - When to Worry

Blue Poop - What Causes It?

You visit the bathroom and you are shocked to find that you have blue poop. Find out what could be causing it and whether you need to worry.

Go to Blue Poop - What Causes It?

White Poop - When to Call the Doctor

White poop is normally an indication that you have a health problem but there are exceptions. Find out here when to call the doctor.

Go to White Poop - When to Call the Doctor

Mucus in Stool - Is It Normal?

Mucus in stool can be sign of many different bowel problems. Find out here what could be causing it and if you should be concerned.

Go to Mucus in Stool - Is it Normal?

Blood in Poop - Don't Panic!

Read here about what causes fresh red blood in your poop and which tests you may need.

Go to Blood in Poop - Don't Panic

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