Green Bowel Movement and Green Diarrhea – What Are the Causes?

Varying shades of brown is accepted as the normal stool color but sometimes it may be other colors. Most of these other hues are considered as abnormal. One of these abnormal colors ia green tinge to overtly green color of the bowel movement. It has to be investigated as this can be a sign of various diseases. The condition is even more serious if there is diarrhea that is green.

Most of the time green bowel movement and green diarrhea are thought to be due to bile. This is the substance that is produced by the liver and stored in the gallbladder. Bile is naturally a greenish color and released into the small intestine during the digestion of food. However, bile is reabsorbed and also processed by colonic bacteria which yields a yellow to brown color that gives stool its natural color.

Causes of a Green Bowel Movement

Green bowel movement that is of normal consistency and not overly frequent like in diarrhea is mainly due to strong dyes or colorants staining the stool a green color. This may arise with certain foods, beverages, medication and supplements. Sometimes these substances are not green in color but with digestion and interaction with other substances in the bowel, these substances may make the stool appear green in color.


Green bowel movement may be normal for a person that ingests a lot of:

  • Green leafy vegetables like broccoli, lettuce, spinach, cabbage
  • Black licorice
  • Baby formula – vegetable mashes
  • Artificial colors, commonly added to ice creams, soda, fruit juices, or other drinks, morning cereals, milk products, sweets, etc.
  • Iron-rich foods like enriched breakfast cereals, red meat, spinach, beans, etc.

Dark green color may persist for up to five days after ingesting above mentioned foods. Supplements or artificial colors may give bright green color to the stool.

In infants, stool is green in the first few days after birth. This is normal. It may also occur later in infancy due to breastfeeding. Some baby formulas may also cause a green color f infant stool. Children on a clear-liquid “starvation diet” during illness may have green watery stools since bile is the only substance that is passing through the gut and out of the bowels.

Medications and Supplements

Certain medication and supplements, that are taken orally, may cause green bowel movement for several different reasons. The following drugs and supplements are more likely to cause green bowel movement:

  • Iron supplements
  • Laxatives – due to shortened bowel transit time (movement through the gut).
  • Algae
  • Chlorophyll
  • Children syrups often contain sweeteners fructose or sorbitol that both can speed up peristalsis what may result in green bowel movements.
  • Vitamins /mineral supplements, or eventually any other medication or supplement taken by mouth, if it is artificially colored, or if it contains fructose or sorbitol, that may speed up movement through the bowels.

Causes of Green Diarrhea

Sometimes an abnormally green color of the stool is also associated with diarrhea. Therefore the diarrheal stool apears green in color. In these cases the greenish hue may be due to the unprocessed bile or due to other causes that can taint the stool green while causing diarrhea simultaneously. For example, a green colored alcoholic beverage like sambuca can cause diarrhea when consumed in excess while tainting the stool with its strong green color.

Decreased Bowel Transit Time

Green bile, after excretion from the liver into duodenum, slowly changes to yellow, and then to brown color due to chemical changes performed by normal intestinal bacteria and enzymes. When the bowel content flows through the intestine fast, original bile color does not change, resulting in green or yellow stool. Causes of decreased bowel transit time include:

  • Diarrhea – loose bowel movements; there are several causes of loose bowel movements, including food poisoning (giardia and salmonella infection often result in green diarrhea), rotavirus infection, food allergies, lactose intolerance, fructose malabsorption, celiac disease, Crohn’s disease, ulcerative colitis, and so on.
  • GERD (Gastro-Esophageal Reflux Disease) is where there is reverse flow of stomach acid and in some instances there may be associated diarrhea which can be significantly stained with bile.
  • Thyrotoxicosis – elevated levels of hormone thyroxine in the blood, usually due to autoimmune thyroid disorder (Grave’s disease)
  • Impaired gut innervation, common in diabetes when a condition known as diabetic neuropathy occurs. This alters bowel motility.

Impaired Bile Re-absorption in the Small Intestine

As bile passed down the gut, it is processed by the digestive system. Bile salts that are in the bile and largely responsible for its green color is reabsorbed to some extent. It is then processed again by the body. Bile salts are absorbed into blood mainly from last part of small intestine (terminal ileum). Causes of impaired bile re-absorption includes:

  • Inflammation of the small intestine, mainly due to Crohn’s disease
  • Surgical removal of the terminal ileum

Some of these bile salts are then secreted again in to the bowel through the bile or processed by the kidney and expelled with urine.

What to Do, If You Have Green Bowel Movements?

Green bowel movements due to ingested food or medication/supplement are normal, and may not require any medical intervention. The stool will return toa  normal color once the causative substance is flushed out of the digestive tract. However, medication and supplements should not be stopped until a doctor or pharmacist advises so. Green bowel movement is not always serious in these cases but should nevertheless be investigated if it is persistent.

In all other cases, especially if symptoms like fever, diarrhea, constipation, weight loss, or general malaise are present, then it needs to be investigated by a medical professional. Sometimes this greenish stool can be due to a serious underlying disorder. It is important to bear in mind that greenish bowel movement is just a symptom some underlying condition or temporary disturbance. A stool sample may have to be collected and sent to a laboratory for analysis.

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  • Natalie


    When I eat pasta, I make my own sauce. I fry up onions, mushrooms, garlic and sweet red peppers in olive oil (a lot of olive oil btw) and add canned tomato sauce. After about 30 minutes I get watery BMs. This only happens after I eat this meal.

  • Jan Modric


    you can remove ingredients one by one from the sauce to see which one affects you…

  • steve

    For three days I have had green/yellow diarrhea. I have been drinking lots to stop myself being dehydrated, and I’ve been eating simple meals such as beans on toast.
    I feel that I might have food poisoning from pasta I had a day before I got the diarrhea. A friend cooked a dish consisting of chorizo sausages, tomato, peppers and pasta.
    Though I had cinema popcorn on the same day.

  • Jan Modric


    bacterial food poisoning could result in a green/yellow diarrhea, which should stop on its own within a week without any treatment. Sausages/pasta sounds much more likely cause than popcorn to me. Doctors now advise a regular diet (what you feel comfortable with) during diarrhea. Water or a sport drink (with sodium and glucose) is good for rehydration in mild diarrhea. If diarrhea doesn’t stop in a week, I recommend you to visit a doctor and consider the possibility of a parasitic infection.

  • JimSamson

    I’m a 22 year old male who works 11 hour days and has a pretty bad diet. for the past 4 days I’ve had diarrhea with high fever(went away after 24 hours) but on the 4th day(today) I had slightly loose stool that was 100% pure emerald green. Is this a sign of something very serious? or is it just diet/food poisoning. I’m actually quite nervous it’s been 4 days the movements are much further apart just alot of cramps (feels like trapped gas) Should i be alamred by any of this or am i just getting over a case of food poisoning?

  • Jan Modric


    bacterial food poisoning usually heals on its own within a week. If not, intestinal parasites (like giardia) can be suspected – for this a stool test and appropriate treatment is recommended otherwise the infection may last for weeks or months. Another possibility would be Clostridium difficile (bacterium) overgrowth in the colon (a special stool test is needed for the diagnosis) – if your temperature rises again, I recommend you to visit a gastroenterologist right away.

  • Mommyb

    Ok-my little boy 12mo had a fever of 104.3 yesterday and did nothing but sleep and let me hold him. He drank well and ate 2 popice’s so he stayed well hydrated. He ate slightly less than normal, but not a really significant amount less. His only other symptoms are a clear runny nose and gas (and seems to strain when he toots). He hasn’t pooped in 3 days. The week leading up to this he had a BM everyday, most days 3 times. This I’d much more than normal for him-typically it’s about 3x a week. So I finally gave him a suppository and he cried when he went. It was pretty watery and bright green/yellow in color with two pieces in it that were the consistancy of really thick icing or toothpaste. I noticed the area surrounding is penis looked swollen. So I mashed on it a little, and it felt kind of full. He was already upset from popping so he was crying, so I couldn’t tell if this bothered him. However, to be honest, I haven’t seen enough men to know what’s “normal.” I don’t really examine my husband so I just don’t know. Thoughts?

  • Jan Modric


    if you suspect that the area around his penis is inflamed, please take him to the doctor as soon as possible. His condition could be caused by a certain viral infection, but I cannot determine this in more detail. Two thick pieces in his stool could be from the suppository, food, but I cannot exclude intestinal worms.

  • heather

    Hi Alex,
    Interesting all the blood works said negative to celiac disease, how did they test you for the celiac gene, did your doctor do it or did you request for it to be done as my daughters came out negative but she gets really bloated, you can see it like u are pregnant, she is much better at the moment she said she thinks it is the milk like chocolates etc, but the test for all this came negative. gastroscopy showed mild gastritis, did not have a colonoscopy done, all started in 2012 June and still comes on and off she is ok with glueten products but drinking or eating milk tends to irritate her stomach that is what she says but there are times she will have a couple of chocolates pieces and ok then she had about 5 pieces and it started to bloat is this common if you have IBS or celiac Thanks HG

  • Gia

    Green stool can also be caused by an overactive thyroid. It speeds up everything in the body and so the bile doesn’t get processed and the stool remains green vs turning brown. Other things you’d notice with a fast thyroid are weight loss, much more frequent defecation, like 4-5x a day, overall itching, faster heartbeat, swollen ankles and shaking…

    I know 1st hand cause i have Graves.

  • Nicole Woolard

    I have had loose bowels that are a blackish green and cramping in my stomach since Saturday. I do not feel bad other than that. As soon as I eat it goes right through me. Today makes day 5. Should I call the doctor?

  • Soul intentions

    So I just started having green bowel movements today .At least 5. very strange because I usually only go once maybe twice a day. The first time, it was solid, and the rest not so much. The last few came almost suddenly and could not be ignored. I haven’t eaten anything green nor a taken any suppliments . except for some olives 4 days ago. I’ve eaten way more olives than that before without the green “results” .I’ve gone since then and my bowels were not green , but normal. I feel I may be pregnant , but it’s very doubtful .I have some signs but not all . because PMS signs resemble early pregnancy signs extremely closely, it’s hard to tell and I don’t know what to think at this point. Work is slow and I can’t afford a Doctor at the moment. If there’s input or something I can be given , that would be great. Either in pregnant or something’s wrong with me because the whole green thing is very sudden and strange. The last time I went green I took one too many iron pills. That was years ago.