Can omeprazole change your stool color? (yellow, black, green stools, and more).

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

Summary (what you need to know):

Omeprazole is a drug that reduces stomach acid. It is used to treat different conditions such as stomach ulcers, acid reflux (GERD), H. Pylori, and functional dyspepsia).

Stool color changes are not a common side effect of omeprazole. Instead, most cases are due to causes other than omeprazole, such as dietary changes, infection, and others.

1 . Omeprazole yellow stool.

Omeprazole reduces the stomach acid to treat diseases such as peptic ulcers and acid reflux (GERD).

However, Prolonged acid inhibition with long-term omeprazole use may have its drawbacks.

Long-term omeprazole use may cause chronic diarrhea or loose stool, which manifests as a yellow or pale stool.

However, yellow stool is a widespread finding among people, even healthy individuals.

Below are the most common causes of yellow stool with omeprazole treatment. But not that some are due to omeprazole effects, while others are not related to omeprazole.

A . Long-term use of omeprazole (more than eight weeks).

Long-term use of omeprazole is associated with gastrointestinal side effects such as small intestinal bacterial overgrowth (SIBO) and chronic diarrhea or loose stool (reference).

The link between SIBO and Omeprazole use is still unclear. However, diarrhea with long-term use of omeprazole is common (reference).

Diarrhea or loose stool due to long-term omeprazole use causes yellow or pale stool.

The yellow or pale color of the stool is due to the speeding up of the stool inside your digestive tract. When the stool stays for shorter periods, it will not have enough time to acquire its standard brown color.

B. Dietary factors.

If you have a yellow stool during omeprazole treatment without diarrhea or other symptoms, you should consider yellow foods to cause your yellow stool.

Many dietary factors may cause pale or yellow stool color independent of omeprazole. 

For example, Eating too much:

  • Carrot.
  • Sweet Potatoes.
  • Tumeric
  • Yellowish food additives or juices.
  • High-fat diet.

C. Associated chronic diarrheal diseases.

Any disease that causes chronic diarrhea or loose stool can also cause yellow stool while taking omeprazole. Chronic diarrhea or loose stool leads to the persistent yellow color of the stool.

These diseases are very common and often overlooked. For example:

  • Associated Irritable bowel syndrome with predominant diarrhea.
  • Associated food intolerances such as lactose intolerance (in milk and dairy products), fructose intolerance (in fruits and honey), and others.
  • Bile acid diarrhea.
  • Celiac disease, and others.

D. Associated acute diarrhea.

Sudden yellow watery stool for a few days can be due to associated infection (Commonly, viral gastroenteritis and giardiasis). Acute gastroenteritis is common and is a famous cause of yellow stool color in people who are taking omeprazole.

When to see a doctor for yellow stool while taking omeprazole?

A single or few episodes of yellow stool while you’re on omeprazole or other PPIs (such as esomeprazole or pantoprazole).

  • Severe diarrhea.
  • Fever.
  • Jaundice.
  • Blood or mucus in the stool.
  • Severe abdominal cramps.
  • Vomiting.


Yellow stool with omeprazole can be due to simple causes such as dietary changes. However, it can also be a sign of diarrhea due to long-term use of omeprazole, infections, associated IBS, and acute gastroenteritis.

2 . Black stool and omeprazole.

Omeprazole is not known to cause black stools.

First, You have to differentiate between a very dark brown well-formed stool and a black tarry stool.

A very dark brown stool (almost black) well-formed stool is often due to dietary factors or taking supplements (such as iron).

a Jet-black, tarry stool is a sign of gastrointestinal bleeding. Many people who take omeprazole may have stomach or duodenal ulcers. The bleeding ulcer may cause black tarry stools in people who take omeprazole.

The symptoms of bleeding peptic ulcer include:

  • severe pain in the upper central abdomen (epigastric pain).
  • Vomiting of blood (may be absent).
  • Black tarry stool.
  • Nausea.
  • Loss of appetite.
  • Dizziness and fatigue.
  • Shortness of breath and fast heartbeats.
  • Pale skin.
  • In severe cases, signs of shock may develop (fainting, confusion, and loss of consciousness).

Seek urgent medical help if you think you have a bleeding peptic ulcer.

Other causes of black stool during omeprazole therapy:

  • Black foods such as Black licorice, blueberries, grape juice, chocolate sandwich cookies, beets, etc.
  • Some supplements and medications such as Pepto-Bismol and iron-containing supplements.

Learn more.

3 . Green stool during omeprazole treatment.

The greenish stool isn’t a reported omeprazole side effect. Green stool is commonly caused by food such as green leafy vegetables. It also can be a consequence of severe watery diarrhea.

Learn more about green stool HERE.