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10 Key Signs of SIBO – Could A SIBO Diagnosis Be The Answer?

SIBO is a relatively overlooked condition so I’m here to tell you what signs of SIBO to look for. Could a SIBO diagnosis be the answer to your gastrointestinal problems? This post is for you if you have recurrent bowel issues with no diagnosis or no relief from symptoms. In this post I will provide 10 of the key signs that this could be a condition that affects you.

What is SIBO?

SIBO is Small Intestinal Bacterial Overgrowth. It is a serious medical condition where an excess of bacteria in the small intestine builds up and causes gastrointestinal symptoms. It has been shown that 60-80% of those with IBS may actually have SIBO1. To read more about SIBO and what it is, see our previous blog “What is SIBO?”.

10 Key Signs of SIBO

SIBO is a condition which could be present in people with other gastrointestinal conditions (such as IBS, Coeliac disease and more). The type and amount of symptoms can depend on the degree of inflammation in the gut, the amount of bacterial overgrowth and the type of bacteria that is growing there2. Although there is a long list of possible signs and symptoms, these can appear in isolation or as a combination.


1. Bloating and Wind
A key symptom of bacterial overgrowth is often bloating and wind. This occurs as the bacteria growing in the small intestine can ferment carbohydrates in this part of the gastrointestinal tract causing a release of gas3. This excess gas can build up and cause distension (bloating) and flatulence. These symptoms can be very uncomfortable and cause self-consciousness too.

2. Abdominal Cramps and Pain
There are several mechanisms by which abdominal pain may occur in those with SIBO. It is possible that the aforementioned bloating can cause uncomfortable distension of the stomach and upper gut and this can be painful4. The excess gas can really stretch the intestinal walls and cause debilitating pain. It is also possible that there is a malfunction in the motility of the gut which can cause pain and also be a cause of SIBO.

3. Diarrhoea
As with all the above symptoms, diarrhoea can be caused by other conditions, but it is also a sign of SIBO. SIBO alters the function of the gut and can cause issues throughout the gastrointestinal tract. The bacteria breaking down foods in the small intestine can release toxins which trigger diarrhoea2, this could also result from malabsorption. Severe diarrhoea can be painful, disruptive and difficult to deal with.

4. Constipation
Another common sign of the condition is recurrent constipation, although this is less common in SIBO than diarrhoea. Some gases are released which slow the transit of food in the gastrointestinal tract causing constipation. For example, bacteria that produce methane are more likely to cause constipation whereas bacteria producing hydrogen cause more diarrhoea4. Constipation is common in the population, if you find yours worsens with an increase in fibre in your diet, it could well be a sign of SIBO.

5. Nausea
Those with SIBO will often suffer from nausea2. This could be caused by the build up of gas, causing discomfort and pressing on the stomach causing the feeling of sickness. It could also be caused by the altered gut movement in those with SIBO. Regardless, it is not pleasant and causes issues with eating a balanced diet.

6. Fatigue and Brain Fog
SIBO can lead to increased tiredness, sustained fatigue and brain fogginess. This is often a very debilitating symptom which can severely affect daily life. There could be several reasons why SIBO leads to fatigue, such as lack of energy being absorbed from foods, a secondary side effect from gut issues or ongoing concerns and stress from the condition5. However, this is an area of growing research.

7. Unintentional Weight Loss
SIBO can cause inflammation in the gut. This is because the growing colonies of bacteria cause irritation, release toxins and cause issues from being in the wrong part of the gut. This causes an increase in inflammation. Chronic inflammation can lead to damage of the gut lining6. This can mean that you struggle to absorb nutrients. This can lead to unintentional weight loss which can be serious and can occur quickly. If you ever experience a sudden unexpected loss of weight, please speak to a GP or dietitian.

8. Fat Malabsorption
As mentioned above, SIBO can result in absorption issues in the gut due to chronic inflammation. Fat is something that is commonly malabsorbed7. This can result in weight loss but also steatorrhoea. This is the presence of excess fat in the faeces; they may be pale, oily and difficult to flush.

9. Nutrient Deficiencies
The aforementioned malabsorption can also lead to various nutrient deficiencies. Vitamins A, D, E and K are fat-soluble; they are transported and absorbed with fat so if you have continued steatorrhoea you could be missing out on key vitamins. Deficiencies of Iron, Magnesium and B12 are common in SIBO too. This is because the bacteria growing in the small intestine use and metabolise these vitamins themselves so they aren’t available for you to absorb7.

10. Rosacea
Rosacea is an inflammatory condition which causes red flushing and is most often seen on the face. This is again an area of growing research but it has been shown that there is a link between rosacea and SIBO8. It has also been shown that treatment for SIBO can lead to elimination of Rosacea symptoms!

It is clear that SIBO can result in a collection of various symptoms. All of the above are signs of SIBO, but also other conditions. SIBO causes dysbiosis of the gastrointestinal tract meaning that there is an imbalance of bacteria which can be why there are so many different symptoms.

If you feel that you suffer from several, or all, of the above symptoms, it may be worth investigating to see if SIBO is the cause. Usually, this can be detected with a simple breath test.



You can book in with the IBS dietitian Bath to see what support you can get, be it at home or in clinic.

The information provided above is not meant for the purposes of medical diagnosis, treatment or prescribing any form of medicine for any condition. This information is not intended to replace the advice of a healthcare professional. Please ensure to consult a qualified health care professional with any questions you may have.

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