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Your guide to the SIBO breath test

Updated: Oct 14, 2023

The SIBO breath test is considered the gold standard for diagnosing a Small Intestinal Bacterial Overgrowth (SIBO). SIBO is a condition that has been estimated to be the cause of Irritable Bowel Symptoms in up to 78% of IBS sufferers.

If there is an overgrowth of one or more bacteria in the upper part of the gut this can lead to symptoms of bloating, abdominal discomfort, belching, flatulence, diarrhea and/or constipation.

SIBO breath test kit
SIBO breath test kit

How does the SIBO breath test work?

The bacteria in the gut produce certain gases when they eat and digest food, particularly food containing fermentable carbohydrates. These gases are not made by the human body itself but by the microflora or bacteria residing in your gut.

The type of gas released depends on the bacteria present. The effects on the body are influenced by the gas produced and its quantity.

Excessive hydrogen gas producing bacteria tend to promote diarrhea.

Those with an overgrowth of methane gas producing bacteria, tend towards constipation.

A third, much rarer type of SIBO can occur with the release of excessive hydrogen sulfide gas. This typically results in diarrhea, though constipation can occur.

The SIBO breath test measures the hydrogen and methane gas produced by organisms in the small intestine that has diffused into the blood, then the lungs for expiration. They are graphed every 20 minutes over a 3 hour period and then compared to a baseline.

What is required to perform the SIBO breath test?

A hydrogen-methane breath test kit can be purchased through certain practitioners to be completed in the comfort of your own home.

The test requires a restricted diet for 24hrs in preparation. A sugary substrate (lactulose or glucose) is drunk to act as a food source for the bacteria, if present in the small intestine. As the bacteria ferment the substrate, any hydrogen and/or methane is absorbed into the bloodstream and exhaled through breath. Breath samples are collected over a 3 hour period.

The following needs to be avoided for 2 weeks prior to completing the test: probiotics,


anti-microbial herbs, and


(Ask your practitioner if you are unsure about what you are taking).

It is also best to wait at least 4 weeks after a colonoscopy, or colonoscopy prep, barium study or colonic therapy.

For 2 days prior to completing the test the following should be avoided:

Proton pump inhibitor medications (such as omeprazole or Losec for reflux), laxatives (ending in -ol or -ose), high dose magnesium and vitamin C.

The strict preparatory diet begins 24hrs prior (or 48hrs before if prone to constipation). An overnight fast occurs 12hrs before the testing begins.

Completing over a weekend can be helpful, starting the diet at 9am on Saturday, fasting for 12hrs from 9pm Saturday and then taking the breath samples from 9am to 12pm on Sunday morning (waking at 8am).

Which foods need to be avoided for the SIBO breath test preparatory diet?

Following the Breath Test Preparatory Diet is VERY important for accurate results.

During the diet preparation period (24-48hrs before) the ONLY food and drink that may be consumed include:

  • Chicken, turkey, fish, lean beef, lamb or tofu.

Fatty cuts of meat and pork (including ham & bacon) should be avoided. Meat can be baked or broiled, or gently fried in a small amount of oil. Vegetarians can have tofu as their protein. Avoid all processed meats or meat-like products.

  • Salt and pepper – no other seasonings are permitted.

  • Plain steamed white rice (NOT Basmati rice. Short or long-grain white rice or jasmine rice is best). The rice needs to be cooked fresh for each meal as reheated rice becomes a resistant starch and can interfere with test results.

  • White rice noodles

  • Plain rice crackers, such as Orgran Gluten Free Rice Crispbread

  • Eggs – cooked any way, without milk of any kind.

  • White bread only (or white rice bread – ensure it has no added starches or dairy products). All bread must be milk, milk powder and dairy free. A quality crusty sourdough is a fairly safe option. A gluten-free bread made with white rice flour and without nuts, seeds, added starches or any milk/dairy should be OK.

  • Small amounts of hard cheese such as parmesan or pecorino for flavouring only.

  • Small amounts of butter, ghee or oil.

  • Weak black tea or coffee, or water. No sugar (stevia is OK).

FRUITS, VEGETABLES, NUTS and SEEDS ARE NOT ALLOWED. If in doubt, it is best to avoid.

Prawns, chicken, beef, fish and eggs.
Some of the foods suitable to eat during the SIBO breath test preparatory diet.

Obviously, foods that are typically excluded from your diet should also be avoided. For example, those with an egg allergy must avoid eggs and those with a gluten sensitivity should avoid normal white bread.

Meal suggestions can be found here.

Consumption of ALL food and drink, except water, must be stopped 12hrs before testing begins. This is the overnight fasting period.

How do you complete the SIBO breath test?

Before beginning the test, you should have:

- been awake for at least 1hr, and

- have avoided exercise, smoking or vaping for 1hr prior to and during the test.

Be prepared with the following:

  • The test kit - which contains either a glucose or lactulose sugar drink to consume during the test.

Test tubes and labels, a blue bag with a test tube port, mouthwash, paperwork, and test instructions are also included.

  • Pen

  • Timer (or use your phone)

  • 3 glasses of water - one full of plain water, one with 250ml of water, and another with 30mls or 2 Tablespoons of water.

To take the first breath sample:

  1. Get comfortable, take hold of the blue bag, and have a test tube on hand.

  2. Take a deep breath and hold for 15 seconds.

  3. Put your lips around the mouthpiece of the blue bag.

  4. Breathe out normally into the bag.

  5. When the blue bag is inflated and while you are still breathing out insert a test tube in the holder on the side and push it right in.

  6. Count to 3 then remove the test tube.

  7. Breathe normally.

  8. Label the test tube as per the instruction guide in the test kit.

A man performing the SIBO breath test
The SIBO breath test

Now, the mouthwash is used.

  1. Mix the supplied mouthwash with the glass with 2 Tablespoons of water.

  2. Now use it to rinse your mouth for 30 seconds.

  3. Swish around your mouth and gargle. (Do NOT swallow).

  4. Spit it out back into the empty glass when finished.

  5. Use a clean glass of water to rinse your mouth.

Next, collect the second breath sample (baseline sample) by repeating the steps above, remembering to hold your breath for 15 seconds before breathing into the bag and inserting the test tube when inflated.

The next step is to prepare the sugary solution for you to drink. This will be either lactulose or glucose. Each has its own limitations and ideally, it is best to complete both separately, however, the practitioner will choose which is right for you. The lactulose substrate is most typically used.

  1. Mix the solution contained in the test kit with 250ml of water.

  2. Drink all of it within 5 minutes.

  3. Set your timer for 20 minutes. This is when the next breath sample will be collected.

  4. If any symptoms are experienced, these are recorded on the paperwork provided.

At the 20-minute mark, take your breath sample as you did before. Be sure to label the test tube.

Set your timer again for another 20 minutes. It is best to do this just before collecting your sample to avoid getting behind.

Take a breath sample every 20 minutes until all the test tubes have been used. It should take around 3 hours to complete.

You can drink water freely after the first hour.

Once completed, use the supplied packaging to wrap the test tubes to send them safely by courier to the lab. A courier label for the box and the phone number to call for collection are included in the kit. Please ensure the paperwork is completed and all test tubes are labeled before adding to the box to be couriered.

The blue collection device can be thrown out and does not need to be returned.

Normal eating and drinking can begin once the test is completed.

How long does it take to get the test results back?

The results are usually sent to your practitioner within 2 to 3 weeks.

Interested in performing a SIBO breath test and looking to uncover the root causes of your health concerns?

Then please get in touch by email at or by booking a free discovery call.

The nourish to flourish IBS Solution

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Stu Mountjoy
Stu Mountjoy
Jul 24, 2022

I actually came to this page, to see if there is ANY evidence about Losec clashing with Stevia? I had two bowel movements, in half an hour of each other, one normal and the other runny, do IBS or SIBO people have that often? I know it clashes with caffeine, LOL, had that experience myself, but how about the sweetener Stevia?

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