What are the symptoms of small intestinal bacterial overgrowth (SIBO)?

Written by: Dr Sebastian Zeki
Published: | Updated: 23/03/2023
Edited by: Carlota Pano

Gut bacteria is key to maintaining healthy digestion. A change in the delicate balance of gut bacteria, such as in small intestinal bacterial overgrowth (SIBO), can thus result in associated gastrointestinal symptoms, which may require treatment.


Here to provide an expert insight into SIBO, including causes, symptoms and treatment, is Dr Sebastian Zeki, renowned consultant gastroenterologist based in London.



What is small intestinal bacterial overgrowth (SIBO)?


SIBO, or blind loop syndrome, is a condition that occurs when there are excessive bacteria in the small intestine - particularly, the types of bacteria that would usually be found elsewhere in the gastrointestinal tract.


What are the symptoms of SIBO?


SIBO typically causes abdominal pain and diarrhoea.


Other symptoms may include:


As the bacteria begins to drain away the body’s nutrients, the malabsorption of multivitamins and minerals may cause malnutrition and unintentional weight loss, as well.


What causes SIBO?


Bacteria tends to overgrow when there is slow movement of food and waste material through the gastrointestinal tract. Although the exact reason for this still remains unknown, the overgrowth can also be caused by nerve damage, muscular malformation in the intestine, or pH changes in the small bowel.


In SIBO, the condition can develop due to a health complication after gastrointestinal surgery, or due to underlying anatomical and medical conditions that increase a patient’s risk of developing SIBO.


These conditions include:


Acid-reducing medications, as well as narcotic medications that slow down the process of digestion, are also contributing factors for the development of SIBO.


How is SIBO diagnosed and treated?


To diagnose SIBO, a specialist will carry out several investigations, such as:

  • a physical examination of the abdomen
  • a blood test
  • a breath test that checks levels of hydrogen and methane (two by-products of bacterial overgrowth)
  • a faecal sample


Once a diagnosis is confirmed, treatment for SIBO involves a simple course of antibiotics, and/or changes in diet if necessary.



If you require expert diagnosis and treatment for symptoms of SIBO, do not hesitate to visit Dr Zeki's Top Doctors profile today.

By Dr Sebastian Zeki

Dr Sebastian Zeki is a leading consultant gastroenterologist with over 20 years of experience. He is highly experienced in a wide range of gastroenterological conditions and treatments, with his areas of expertise including acid reflux, bloating, abdominal pain, cancer, food intolerance and colonoscopies.

Dr Zeki first graduated with an MBBS from University College London in 2001. He then went on to receive an MSc in Health Informatics from City, University of London and a PhD in Molecular Biology from Queen Mary University of London in 2013. He is also a member of the Royal College of Physicians.

Dr Zeki currently practices privately at London Bridge Hospital and HCA UK at the Shard. At London Bridge Hospital he specialises in both diagnostic gastroscopy and diagnostic colonoscopy. At HCA UK at The Shard, he offers treatments for all of the conditions mentioned above.

In addition to his clinical work, Dr Zeki is also a renowned medical educator. He served as a clinical lecturer at the University of Cambridge’s MRC Cancer Unit from 2013 to 2015. He currently serves as an honorary senior lecturer at both King’s College London and Barts Cancer Institute, London. 

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