Why does overgrowth syndrome occur?

Overgrowth syndrome (small intestinal bacterial overgrowth syndrome, or SIBO) is when the small intestine is colonised by the wrong sort of bacteria, which are not present there under normal circumstances (or not in such volumes) and permanently disrupt the digestive process.

It involves a significant migration of gut bacteria from the large to the small intestine. It is currently assumed that the large intestine is home to upto 1000 different types of bacteria. These are also called gut flora. Far less bacteria settle in the small intestine. Severe symptoms may result if large numbers of the wrong types of bacteria migrate from the large to the small intestine and overwhelm the bacteria which are settled there.

Complaints caused by overgrowth syndrome

Patient’s symptoms range from complaints such as tympanites (meteorism), foul-smelling faeces, painful abdominal bloating, bad breath and perhaps even continued weight loss or severe fatigue. This inflammation also results in a tendency towards pulpy and greasy stools. As the disease progresses, the intestine becomes fatigued, with insufficient production of intestinal juices and persistent constipation.

Patients frequently suffer complaints due to a range of foods, such as carbohydrates (sugar), proteins and/or fats. Often, it is the so-called “healthy” and fibre-rich foods which cannot be digested.

Medical history, testing and diagnosis

Because other digestive disorders or food intolerances can also cause this, testing and diagnosis is usually done after a very detailed consultation during which the patient’s medical history is taken down. Valuable information such as use of antibiotics, symptoms occuring after meals, lifestyle, stress factors, composition of meals and dosage is collected.

The methane breath test is a classic test procedure. This test is based on a measurement of the methane formed (CH4) from the bacterial decomposition in the digestive tract of the sugar ingested as part of the test. If sugar is not properly digested or if there are bacteria in the small intestine, methane is formed which then gets into the breath via the blood and the circulation.

Because overgrowth syndrome produces CH4, this cannot be diagnosed with the classic hydrogen breath tests.

Mo-Fr 7 am – 4 pm
please use E: termin1090@ihrlabor.at
or call T: +43 1 408 31 31

Beginning and duration of test:
Mo-Fr 8 am – 10:30 am
Duration of test: 2.5 hours


  • Please fast for at least 14 hours before the test – the longer you fast, the better (during this time, you may only drink tap water)
  • On the evening before and on the day of the test, please do not brush your teeth, or use any mouthwash and do not chew chewing gum or eat any sweets
  • Do not smoke for at least 12 hours before the test
  • Do not take any diarrhoea medications (e.g. Imodium)
  • On the day before the test, you can have breakfast as usual
  • At lunchtime and for the 14 hours prior to the test you may not eat any carbohydrates (e.g. noodles, rice, potatoes, bread and bakery products), or any dairy products, fruit or sugar

Please avoid the following foods and beverages:

  • Pasta or noodles, rice, potatoes, bread
  • Sweets, e.g. cakes, biscuits, ice cream
  • Vegetables, e.g. carrots, pumpkin, peas, sweetcorn, kohlrabi, radishes, peppers, cucumbers, beans, cauliflower, cabbage, onions
  • Dairy products (including lactose free products): yoghurt, cream pudding, whipped cream, butter, cream, milk
  • Meat: pork, beef, veal, sausages, bacon, game
  • Canned fish, seafood
  • Fruit, e.g. dried fruits, canned fruits, apples, pears, bananas, strawberries, melons, grapes
  • Beverages: alcoholic drinks, fruit juices, carbonated drinks, tea

You can eat and drink the following:

  • Fish & poultry, fried or steamed
  • Steamed courgettes, broccoli, green salad with oil (no vinegar), avocado, eggs (e.g. scrambled eggs)
  • Beverages: tap water or still mineral water

EUR 40

Payment options:

  • Cash
  • Debit card
  • Credit card (Visa, Mastercard, V-Pay)