SIBO vs. IBS: What You Need to Know for Improved Gut Health


“About three-quarters of patients - as many as 30 million Americans - who have met the diagnostic criteria for IBS have taken a breath test that suggests they have SIBO.”

- Dr. Mark Pimentel and Dr. Ali Rezaie, The Microbiome Connection

This is a staggering number of people who have repeatedly asked their doctors what is wrong with them, often being told that their persistent bloating, constipation, or diarrhea is all in their heads.

Since the discovery of the gut microbiome and its effect on overall health, researchers have begun to unravel the mystery of these seemingly unexplained gastrointestinal symptoms. 

The experts at Good LFE are driven to show sufferers of IBS, SIBO, and other gut health issues how to put the joy back in eating, without having to worry about where the closest bathroom is. The first step is finding out if you have SIBO or IBS, or perhaps, IBS as a result of SIBO. In this article, we explore the differences and similarities between these two gastrointestinal conditions to help you learn more about what might be causing the debilitating symptoms that currently control your life.

What is IBS?

First, it is important to note what IBS is not. Contrary to what your doctors may have told you, Irritable Bowel Syndrome (IBS) is not a psychosomatic condition caused or exacerbated by anxiety and stress. To reiterate, IBS is not “all in your head.”

“The notion that stress can lead to IBS symptoms is one reason so many IBS patients have felt stigmatized and ostracized.”

- Dr. Mark Pimentel and Dr. Ali Rezaie, The Microbiome Connection

What, then, is IBS? Irritable bowel syndrome is a group of symptoms that occur together, including repeated pain in your abdomen and changes in your bowel movements, which may be diarrhea, constipation, or both. With IBS, you have these symptoms without any visible signs of damage or disease in your digestive tract. 

IBS Symptoms

In many cases, the symptoms of IBS may seem contradictory. However, if you have been experiencing the following for at least three months, you may have IBS:

Digestive Symptoms:
  • Abdominal pain or discomfort
  • Diarrhea
  • Constipation
  • Alternating diarrhea and constipation
  • Bloating
  • Excessive gas
  • Urgently needing to defecate
  • A feeling of incomplete evacuation after defecating
  • Relief or worsening of abdominal pain after going to the bathroom
  • Feeling full even when you have not eaten much
Non-Digestive Symptoms:
  • Brain fog

Your IBS symptoms are unique to you and tell your doctor which of the three types of IBS you have. 35% of patients have IBS-C (with constipation), 40% have IBS-D (with diarrhea), and 23% have IBS-M (mixed - both constipation and diarrhea). It is important to note, though, that these symptoms are shared with several other gastrointestinal disorders, so a thorough examination or blood test, like ibs-smart®, is needed to confirm a diagnosis of IBS.

Causes and Triggers of IBS

Until recently it was thought that IBS was caused by psychological stress. However, research now shows the symptoms can be explained by several other factors, including food intolerance, infections in the gastrointestinal system, inflammation, genetic factors, changes in bile acid metabolism, food poisoning, an imbalance in gut microbiota, and small intestinal bacterial overgrowth (SIBO).

What is SIBO?

“SIBO is, in effect, a phenomenon of bacteria dislocated from your large intestine to your small intestine.”

- Dr. Mark Pimentel and Dr. Ali Rezaie, The Microbiome Connection

Small Intestinal Bacterial Overgrowth (SIBO) is a disease of the gastrointestinal system that occurs when the bacterial count in the small intestine surpasses 1000 bacteria per milliliter. It's not an infection but rather a condition where bacteria from the large intestine migrate and proliferate uncontrollably in the small intestine. This often leads to symptoms resembling those of Irritable Bowel Syndrome (IBS). Interestingly, SIBO can be viewed as a subset of IBS, with approximately two-thirds of IBS patients also having SIBO.

Symptoms of SIBO

SIBO causes a range of symptoms in the gut as well as throughout the body, as listed below:

Digestive Symptoms:

  • Abdominal bloating and distension
  • Abdominal discomfort and/or cramps
  • Excessive gas leading to belching and/or flatulence
  • Change in bowel movements: constipation, diarrhea, or both
  • Heartburn and/or acid reflux
  • Nausea

Non-Digestive Symptoms:

  • Brain fog
  • Fatigue
  • Headaches
  • Weight loss/gain
  • Joint pain
  • Mood symptoms
  • Nutritional deficiencies, including iron and B12
  • Skin problems, such as eczema and rashes

Causes and Triggers of SIBO

There are many causes of SIBO, which can include altered gut motility (the movement of food through the intestines may be too slow or too fast), gut obstruction, weight loss surgery, scarring in the abdomen, endometriosis, inflammatory diseases, diabetes, autoimmune diseases, and several drugs including narcotics and prescription medication. Food poisoning can also be responsible for SIBO. While identifying the root cause of your SIBO can be helpful, it’s oftentimes extremely difficult to pinpoint. However, if you are able to definitively identify your root cause, it’s extremely helpful for limiting opportunities for relapse.

SIBO vs. IBS: Similarities and Differences

Recognizing the connection between IBS and SIBO is critical to the management of persistent debilitating gastrointestinal symptoms. As doctors Mark Pimentel and Ali Rezaie explain in their book, “The Microbiome Connection,” “IBS is the disease; SIBO is the elevated cluster of organisms in the gut that cause symptoms defined as IBS.”

Diagnosis and Treatment of SIBO and IBS

One of the biggest differences when comparing SIBO vs. IBS is how each condition is diagnosed. If you’ve had a bout of food poisoning followed by the development of IBS symptoms, your doctor may suspect that you have SIBO. In that case, a simple breath test or bacterial culturing can be used to confirm your diagnosis.

“The primary - and easiest - method of diagnosing SIBO is through a breath test.”

- Dr. Mark Pimentel and Dr. Ali Rezaie, The Microbiome Connection

Bacteria produce hydrogen, methane, and hydrogen sulfide, three gases not normally found in high concentrations in your breath. If the amount of these gasses increases dramatically throughout the test, it is a sign that you have Small Intestinal Bacterial Overgrowth.

On the other hand, if your symptoms are not caused by SIBO, your doctor may go through a process of elimination, ruling out conditions such as inflammatory bowel disease and celiac disease. Your medical history is also an important tool doctors use to compare your symptoms to the Rome IV criteria for the diagnosis of IBS. They state that you must have experienced abdominal pain at least once a week for three months along with two or more other symptoms. 

Treatment options for SIBO include an elemental diet, medication, supplements, and low fermentation eating (LFE) for long-term management. For IBS without SIBO, management options also include dietary changes and medication, as well as probiotics, prebiotics, and fiber supplements.


While there is a significant overlap between the two conditions, there are some important differences that must be considered for the management of your gastrointestinal symptoms. A breath test can easily pinpoint the location of bacterial imbalance in the intestines, enabling you to get the right management plan to improve your quality of life. 

More SIBO Resources

Breath Testing for SIBO

Breath testing is the primary – and easiest – method of diagnosing SIBO. Learn more about this non-invasive diagnostic method.

LFE low fermentation eating cookbook and mircobiome connection book for gut wellness and health

LFE Books

Learn about SIBO, IBS and your microbiome in The Microbiome Connection and then treat your GI system with delicious food from our cookbook.

sibo safe foods for gut health recipes

SIBO Friendly Recipes

Pulled from our cookbook and Krystyna's kitchen, these delicious and SIBO friendly recipes use Low Fermentation Eating to balance your microbiome.