Narrow Stools: Causes, Symptoms, and Treatments

Medically Reviewed By Cynthia Taylor Chavoustie, MPAS, PA-C
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Narrow stools occur due to changes in bowel movements. They can be harmless, occurring as a result of a low fiber diet or temporary infection. However, narrow or pencil-thin stools may also indicate an underlying condition, such as irritable bowel syndrome or colorectal cancer. If narrow stools occur infrequently, they are typically not a cause for concern. If they persist for more than a week, however, this could be a sign of a medical condition.

You may also experience other symptoms alongside narrow stools. These symptoms can include diarrhea, constipation, blood in the stool, or changes in stool color.

Read on to find out what causes narrow stools, as well as information about related symptoms and when to see a doctor.

What are narrow stools?

There is a pencil.
Sean Locke/Stocksy United

A low-caliber stool appears thinner or narrower than usual. They can occur with bowel movements that are either more or less frequent than you are used to.

Changes in the stool can occur due to changes in the diet or as an indication of a digestive tract condition. Narrow stools may be harmless, particularly if they occur as a result of a low fiber diet or a temporary infection.

However, if narrow or pencil-thin stools persist for more than a week, or if they are accompanied by any other symptoms, this could indicate a more serious underlying medical condition.

View our Digestive Health hub for more information about stool health and looking after your digestive system.

A normal-caliber stool followed by a narrow stool

If you pass a normal-caliber stool, which looks the way you expect it to, followed by a narrow stool, this is typically not a cause for concern.

However, if you experience other symptoms, such as passing blood or changes in the color of your stool, contact your doctor to discuss your symptoms.

What causes narrow stools?

Narrow stools can occur due to a number of reasons. Causes of narrow or stringy stools include the following:

Contact your doctor if you experience narrow stools for more than a week.

When should I contact a doctor?

Thin or ribbon-like stools may indicate an underlying health condition. Contact your doctor if they persist for more than a week.

Other symptoms to look out for include weight loss, constipation, fever, or diarrhea. These could indicate a gastrointestinal disease and you may require medical attention.

What symptoms are related to narrow stools?

Narrow stools that are infrequent and do not last very long are typically not a cause for concern. However, if you pass narrow, stringy, or ribbon-like stools for more than a week and experience related symptoms, this could be a sign of an underlying condition.

Irritable bowel syndrome symptoms

IBS is a common condition, affecting around 25–45 million people in the United States. Alongside narrow stools, symptoms of IBS can include:

You may experience constipation followed by diarrhea. Some people may experience constipation with stomach pain, but no diarrhea.

Learn more about irritable bowel syndrome in our IBS article.

Colorectal cancer symptoms

Narrow stools may be a sign of colorectal cancer, also known as colon cancer or bowel cancer. Colorectal cancer typically begins as a polyp, which is a small growth in the wall of the colon. This growth makes a narrower passage for the stool to pass through, resulting in thin stool.

Other symptoms of colorectal cancer you may experience include:

It is possible not to experience any symptoms of colorectal cancer. Regular screenings can help to detect any early signs of the condition.

View our article about colorectal cancer for more information.

Diagnosing conditions related to narrow stool

Your doctor will conduct multiple tests to help to determine the cause of narrow stools and any related symptoms. The tests will depend on which other symptoms are present, but they may include:

  • blood tests to check for anemia, which can be a sign of internal bleeding
  • digital rectal examination, which examines the rectum
  • colonoscopy to examine the colon
  • sigmoidoscopy if the large intestine, or lower part of the colon, needs to be examined

Stool sample analysis

Before your doctor recommends any treatment, they may require a stool sample. They will also explain how to collect and store the stool sample. This process will usually include storing it in a sealed plastic container, labeling it appropriately, and handing it in as soon as possible.

A laboratory will be able to test the sample for any bacteria that may indicate a gastrointestinal complication.

Questions your doctor may ask

To diagnose your condition, your doctor will ask you several questions related to your narrow or stringy stools. These questions may include the following:

  • When did you first experience narrow stools?
  • Have you noticed any other changes in your stool or bowel habits?
  • Are you having pain or discomfort anywhere?
  • Do you have any other symptoms?
  • Have you had these symptoms before?
  • What medications are you taking, if any?

If you have any specific questions you would like to ask your doctor at your consultation, write them down beforehand. This will help you to prepare ahead of your appointment.

Treatments for narrow stools

If narrow stools only occur infrequently and for a short time, it is unlikely to be a cause for concern, and treatment is not necessary.

However, if narrow or pencil-thin stools occur as a result of an underlying medical condition, then your doctor will advise the best treatment for that condition.

IBS treatments

Treatments for IBS differ from person to person, but generally include dietary changes, such as eating freshly prepared meals and avoiding foods that can trigger the condition.

Certain medications may also help to reduce symptoms of IBS. Hyoscine butylbromide (Buscopan) can help to ease bloating and cramps. Loperamide can help to ease diarrhea.

Colorectal cancer treatments

If narrow stools are a symptom of colorectal or bowel cancer, treatment options will depend on how far the cancer has spread and which part of the bowel it affects.

You may be able to undergo surgery for colorectal cancer. Your doctor may also suggest chemotherapy, radiotherapy, or biological treatments.

Around 92% of people with stage 1 colorectal cancer in the U.S. survive for 5 years or more after diagnosis. Contact your doctor as soon as you experience symptoms so that treatment can begin as quickly as possible.

What does a healthy bowel movement look like?

There is no one rule for what may be seen as a healthy bowel movement. One person’s bowel movements may differ from another person’s. However, you will have your own routine, which may range from passing stool as frequently as three times per day to once every other day.

Routine bowel movements should produce soft or firm stools. They should not be too solid or too watery.

It is important to note any persistent changes in your own bowel movement routine. Paying attention to bowel movements and noting any changes can help to detect any underlying health conditions that may require medical attention.


Narrow stools are often harmless. They can occur as a result of a low fiber diet or a temporary infection, and if they only last for a short period of time they will generally not be a cause for concern.

However, if narrow or pencil-thin stools persist for over a week, they could be a sign of an underlying condition, such as IBS or colorectal cancer. You may experience symptoms alongside narrow stools, such as changes in the color of the stool or the frequency of your bowel movements.

Your doctor will be able to carry out tests to determine the cause of the narrow stools and any related symptoms. Tests may include a rectal examination, colonoscopy, and blood tests. Your doctor will then recommend the best treatment options for you depending on the cause of the narrow stools.

Contact your doctor if you experience narrow stools frequently or for more than a week at a time.

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Medical Reviewer: Cynthia Taylor Chavoustie, MPAS, PA-C
Last Review Date: 2022 Mar 30
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Bowel cancer. (2021).
  2. Bowel habits & aging. (n.d.).
  3. Bristol stool chart (2022).
  4. Colorectal cancer symptoms: 7 signs to see your doctor. (n.d.).
  5. Diet, lifestyle and medicines. (2021).
  6. Do I have colorectal cancer? Signs, symptoms and work-up. (2021).
  7. Facts about IBS. (n.d.).
  8. How should I collect and store a poo (stool) sample? (2019).
  9. Irritable bowel syndrome. (n.d.).
  10. Panda, H., et al. (2016). Constipation in a 40-year-old woman.
  11. Rawla, P., et al. (2019). Epidemiology of colorectal cancer: Incidence, mortality, survival, and risk factors.