Have you already tested for SIBO, lactose or fructose? Learn how to interpret your results

You took the test. You received it at home. You followed the instructions to the letter. The results report arrived with graphs and technical data... now what?

It is normal to feel a bit lost when opening the results of a breath test. Many users wonder: “What does that hydrogen spike mean?” or “Why is the methane spike and what does it mean? Even if the result comes back negative, the question remains: ”Then why do I feel bad?.

In this article we explain, step by step, how to interpret the results of a SIBO, lactose intolerance or fructose intolerance test. Our aim is to help you understand what is going on in your body and what decisions you can take from here.

What does a typical digestive breath test report include?

Ailin's reports are designed to be as clear as possible, but it is important to know what you are looking at:

• Hydrogen (H₂) and methane (CH₄) graphs: represent the amount of exhaled gas in parts per million (ppm) over time.
• Collection time: data are collected every 25 minutes for 2 to 3 hours. This makes it possible to observe how gas evolves after ingestion of lactitol, lactose or fructose.
• Baseline: the initial gas level before fermentation starts.
• Significant spikes or increases: rapid or progressive increases which may indicate bacterial overgrowth or malabsorption.
• Preliminary interpretation: based on international clinical criteria, it is indicated whether the result is positive, negative or inconclusive.

At what values is the test result positive or negative?

How to interpret the results of the SIBO test

The SIBO test looks for an abnormal increase in hydrogen or methane in the first 90 minutes after ingestion of the substrate (lactulose).

• Positive result:
  If hydrogen increases ≥20 ppm or methane ≥10 ppm within the first 90 minutes, it is considered positive for SIBO.
  If both gases are elevated, this is called mixed SIBO.
• Negative result:
  There are no significant increases in gas in the expected time. This suggests absence of overgrowth, although it does not rule out other causes of discomfort.
• Elevated methane (>10 ppm at any time):
  May indicate a predominance of methanogenic archaea, related to functional constipation.

How to interpret the results of the lactose test

This test assesses whether the body digests lactose, a sugar found in milk, correctly.

• Positive result: Increases in hydrogen or methane ≥20 ppm from baseline within 2-3 hours indicate lactose malabsorption.
• Symptoms during the test:
  Gas, abdominal pain or diarrhoea shortly after ingestion also reinforce the diagnosis.
• Negative result:
  No significant increases → the body probably digests lactose well.

How to interpret the results of the fructose test

This test detects whether your body is absorbing fructose, which is found in fruits, honey, syrups and many processed products, correctly.

• Positive result:
  Increases in hydrogen ≥20 ppm after ingestion indicate malabsorption. Methane may also rise, especially in people with associated constipation.
• Negative result:
  No evidence of abnormal fermentation → fructose is well tolerated.
• Important:
  A mild intolerance is sometimes only detected if it is combined with symptoms, so it is key to note how you felt during the test.

What to do after the test? 3 key steps

1. Review your symptoms together with the report:
   Technical data is important, but your experience also counts. Did you have discomfort during the test, did it coincide with the gas peaks?
2. Avoid jumping to conclusions on your own:
   Although the reports are understandable, medical interpretation is essential in order not to fall into errors or unnecessary restrictions.
3. Request a post-test consultation:
   A bowel health specialist will be able to explain the report to you, confirm the diagnosis and help you make a clear, personalised plan.

What if my report says “inconclusive”?

Sometimes, the results do not show clear increases or sufficient evidence. This may be due to:

• Incorrect pre-test preparation (diet, antibiotics, etc.)
• Altered intestinal transit
• Low gas production by the microbiome

In these cases, it does not mean that you are fine or that the test has failed. It may be necessary to repeat the test, adjust the protocol or assess other causes with professional help.

Conclusion: Your digestive test is not the end, it is the beginning.

Having results in hand is not the end of the process, but the beginning. You now have real, objective data that can help you make scientifically based decisions.

You are not alone. There are clear steps to understand your symptoms, improve your digestion and feel better in your day-to-day life.

Your body spoke to you. Now is the time to listen to it and act with information and professional support.

Reservation your post-test consultation with an Ailin specialist 

[ailin_product_thumb pid=»23432″]

References:

1. Rezaie A, Buresi M, Lembo A, Lin H, McCallum R, Rao S, et al. Hydrogen and methane-based breath testing in gastrointestinal disorders: The north American consensus. Am J Gastroenterol [Internet]. 2017;112(5):775-84. Available at: http://dx.doi.org/10.1038/ajg.2017.46
2. Interpreting results [Internet]. SIBO Center. 2019 [cited 2025 July 4]. Available from: https://sibocenter.com/interpreting-results/
3. Catanzaro R, Sciuto M, Marotta F. Lactose intolerance: An update on its pathogenesis, diagnosis, and treatment. Nutr Res [Internet]. 2021;89:23-34. Available at: http://dx.doi.org/10.1016/j.nutres.2021.02.003
4. Jordan K, Leithold C. Consider fructose intolerance. Dtsch Arztebl Int [Internet]. 2021;118(22):378. Available at: http://dx.doi.org/10.3238/arztebl.m2021.0198