In this article
SIBO and IBS are both digestive conditions, and some of their common symptoms overlap, such as bloating and belly pain. They are not the same thing. Irritable bowel syndrome (IBS) is a group of symptoms that occur together, including repeated belly pain and changes in bowel movements (NIDDK). Small intestinal bacterial overgrowth (SIBO) is a condition in which very large numbers of bacteria grow in the small intestine (MedlinePlus).
This guide explains what each term means and how public health sources describe the connection between them.
What IBS is
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) describes IBS as a group of symptoms that occur together: repeated pain in the abdomen and changes in bowel movements, which may be diarrhea, constipation or both. These symptoms happen without visible signs of damage or disease in the digestive tract (NIDDK).
IBS is a functional gastrointestinal disorder. Doctors now call these disorders of gut-brain interaction, because they relate to how the brain and the gut work together (NIDDK). MedlinePlus describes IBS as a problem that affects the large intestine (MedlinePlus).
Studies suggest that about 12 percent of people in the United States have IBS, and women are up to two times more likely than men to develop it (NIDDK).
What SIBO is
Unlike the large intestine, the small intestine usually doesn't have a large number of bacteria. In SIBO, very large numbers of bacteria grow there. MedlinePlus notes that the extra bacteria may use up nutrients the body needs (MedlinePlus).
MedlinePlus lists several conditions that can lead to SIBO, including (MedlinePlus):
- Diseases or surgeries that create pouches or blockages in the small intestine
- Diseases that slow the movement of the small bowel, such as diabetes and scleroderma
- Some cases of IBS
SIBO and IBS side by side
| IBS | SIBO | |
|---|---|---|
| What it is | A group of symptoms that occur together (NIDDK) | Very large numbers of bacteria growing in the small intestine (MedlinePlus) |
| Part of the gut | The large intestine (MedlinePlus) | The small intestine (MedlinePlus) |
| How it's described | A disorder of gut-brain interaction, without visible damage to the digestive tract (NIDDK) | An overgrowth that can follow other conditions, such as slowed bowel movement or structural changes (MedlinePlus) |
| Commonly reported symptoms | Belly pain, changes in bowel movements, bloating (NIDDK) | Abdominal fullness, belly pain and cramps, bloating, diarrhea, gas (MedlinePlus) |
The symptoms in both columns are common and have many possible causes.
How the two are connected
The two sources describe the link from both directions:
- NIDDK lists small intestinal bacterial overgrowth among several problems that are more common in people with IBS, which experts think may play a role in causing IBS (NIDDK).
- MedlinePlus lists some cases of IBS among the conditions that can lead to SIBO (MedlinePlus).
NIDDK also notes that doctors aren't sure what causes IBS, and that different factors may cause it in different people (NIDDK). How SIBO and IBS relate is still being studied.
When to see a clinician
Questions about digestive symptoms, or about any change in health, are best discussed with a licensed clinician who knows a person's history. In a medical emergency, call 911 or go to the nearest emergency room.
Frequently asked questions
Is SIBO the same as IBS? No. IBS is a group of symptoms that occur together without visible damage to the digestive tract (NIDDK). SIBO is an overgrowth of bacteria in the small intestine (MedlinePlus).
What are the types of IBS? NIDDK describes three types based on bowel movement patterns: IBS with constipation (IBS-C), IBS with diarrhea (IBS-D) and IBS with mixed bowel habits (IBS-M) (NIDDK).
What other names has IBS had? In the past, doctors called IBS colitis, mucous colitis, spastic colon, nervous colon and spastic bowel (NIDDK).
Does IBS damage the intestines? According to MedlinePlus, IBS can cause a great deal of discomfort but does not harm the intestines (MedlinePlus).
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Definition & facts for irritable bowel syndrome.
- NIDDK. Symptoms & causes of irritable bowel syndrome.
- MedlinePlus. Irritable bowel syndrome.
- MedlinePlus. Small bowel bacterial overgrowth.
The information in this article is for general educational purposes only. It is not medical advice and is not a substitute for diagnosis or treatment from a qualified clinician who knows your history. Don't start, stop or change any treatment based on this article. If you think you're having a medical emergency, call 911 or go to the nearest emergency room. Reading this article does not create a clinician-patient relationship with Tenor Health or any provider on our platform.
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