Flat poops can happen due to changes in your diet. Some health conditions, including constipation, can cause long or flat poop. If unexplained changes last a few days, consider talking with a doctor.

Changes in stool consistency and color aren’t uncommon based on what you’ve recently eaten. Sometimes, you may notice that your poop appears especially flat, thin, or string-like. Usually, this variation isn’t cause for worry, and your poop will return to its “normal” appearance shortly after.

However, there are times when consistently flat poops may indicate a more concerning underlying condition. Keep reading to find out what they may be.

A lot of times, your poop looks a lot like your intestines. It’s slightly rounded and lumpy. Flat poop isn’t round. Instead, it’s square or string-like in appearance. Sometimes, you have flat poop along with very loose stool that may include diarrhea.

Flat poop doesn’t have a specific color or frequency. You may notice you experience more flat poops when you’ve changed your diet (such as eaten less fiber). Other times, you may see flat poop in the toilet bowl and can’t link it back to anything you did or didn’t eat.

Here’s what flat poop may look like:

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Flat, rope-like poop

Sometimes, your poop is flat and there’s no underlying cause. Just as your poop can be pebble-sized or different colors, flat poops may be one of the variations you occasionally see. However, if you start having flat poops more often, it may be due to one of the following causes.

Irritable bowel syndrome (IBS)

Irritable bowel syndrome or IBS is a gastrointestinal disorder that occurs due to an interrupted function of your gut and brain. IBS can cause abdominal pain as well as bowel movement changes that include diarrhea, constipation, or both. Those with IBS may experience a variety of stool types, ranging from very large poops to flat ones.

An estimated 12 percent of people in the United States have IBS, so this condition can be a common cause of flat poops and other stool changes.


Constipation can be a common cause of flat stool that is usually stringy in consistency. Constipation can occur when you don’t get enough fiber in your diet to add some extra bulk to your stool. As a result, your stool may be thinner, flat, and more difficult to pass.

Benign prostatic hyperplasia (BPH)

Sometimes, the cause of flat stool isn’t the intestinal tract itself but something around it. This is the case for benign prostatic hyperplasia or BPH. This condition causes the male prostate gland to enlarge. The prostate is positioned just in front of the rectum and below the bladder.

While BPH more commonly affects urination (such as a weak stream when peeing), some people do have symptoms related to passing stool, such as constipation and stool changes like flat poop.

Colorectal cancer

Although rare, it’s possible that thin stool can indicate colon cancer. This is because a tumor may grow in the colon that keeps your stool from moving through in its normal shape.

While colorectal cancer doesn’t always cause a lot of symptoms in its earliest stages, it can also lead to symptoms including rectal bleeding, unexplained weight loss, or problems emptying your stool.

Other possible causes

Flat poop may also be due to any condition that may affect how stool moves through or exits the colon. Examples include:

Even abdominal hernias can cause enough narrowing of stool movement so that stool may appear flat.

Treatments or remedies for flat poop depend upon what caused your poop to be flat in the first place. Your doctor may recommend keeping a food journal and noting when you have significant stool changes so you can identify the potential foods and drinks that may cause your stool to appear flat.

Other interventions are the same as those commonly used to treat constipation and IBS. Examples include:

  • increasing fiber intake by eating more whole grains as well as fruits and vegetables with the skins on whenever possible
  • drinking plenty of water to make stools easier to pass
  • increasing physical activity, which can help increase stool movement through the body
  • taking steps to reduce stress whenever possible, through meditation, journaling, listening to soft music, deep breathing, or other stress-relieving interventions

Some people may also find their stools appear more normal in size when they take probiotics. These are supplements that contains live microorganisms similar to the ones that naturally live in your digestive tract. Probiotics are also present in foods with live and active cultures, such as yogurt and kefir. That said, check the labels before buying to make sure as not all of these foods contain them.

Pencil-thin poop isn’t always cause for concern but you should see your doctor if you are experiencing flat poop and have any of the following symptoms:

  • blood in your stool or on the toilet paper
  • changes in the consistency of your stool, such as increasing diarrhea
  • changes in the frequency of your bowel movements, such as going more or less often
  • feeling like you aren’t fully emptying your stool every time
  • high fever
  • stomach pain or cramping

If you have consistently flat stools for three days or more, it may be time to call your doctor.

Flat poops happen. It’s important to pay attention to any other symptoms you may be experiencing, such as abdominal pain or constipation, to understand the potential cause.

If you’re worried your flat poops could be due to an underlying condition, call your doctor to get checked out. Your doctor may also be able to make recommendations that can help your stool take on a more expected appearance.