Ordering the Leaky Gut Test | Lactulose/Mannitol
The Leaky Gut Test | Lactulose/Mannitol helps measure how well your small intestine absorbs nutrients and keeps unwanted particles out of your bloodstream. This test is often used to check for issues with the gut lining that may lead to symptoms like bloating, stomach cramps, or changes in bowel habits. Interestingly, the test uses two sugars—lactulose and mannitol—because they are absorbed differently, which helps pinpoint where the gut barrier may be weak.
Ordering this test can help you and your healthcare provider:
- Identify if your gut lining is letting larger particles pass through, which may cause digestive discomfort.
- Check for problems with nutrient absorption that could lead to low energy or other symptoms.
- Monitor changes in your gut barrier after starting a new diet or supplement plan.
- Track progress if you are working on gut repair or healing protocols.
- Find out if your symptoms are linked to gut barrier issues rather than other causes.
Who Should Consider Intestinal Permeability Testing
People who have ongoing stomach pain, frequent bloating, or unexplained tiredness may benefit from this test. For example, someone who has tried different diets and still feels gassy or uncomfortable after eating might want to check if their gut lining is letting things through that shouldn’t be there.
Ordering this test may also be helpful in these situations:
- Frequent constipation or diarrhea that does not improve with simple changes.
- Food sensitivities that seem to come and go without a clear pattern.
- Chronic skin issues like eczema that have not responded to typical treatments.
- Unexplained joint aches that are not linked to injury or overuse.
- Someone who has taken antibiotics several times in a year and now has new digestive symptoms.
This test can show if your gut wall is letting in things that may trigger inflammation or immune responses, which can be measured and tracked over time. Delaying this test could mean missing early signs of gut barrier problems, making it harder to address symptoms before they become more difficult to manage.
Preparing for Gut Barrier Function Testing
Fasting is required for at least 8 hours before starting the test, usually overnight, to make sure the results are clear and not affected by recent food. Always follow any instructions your doctor or healthcare provider gives you, as they may have specific steps to help you get the best results from your sample collection.
Labs Included When Ordering Your Leaky Gut Test | Lactulose/Mannitol
| Test Name | Reference Range | What This Marker Means | Low and High Levels of Leaky Gut Test | Lactulose/Mannitol |
|---|---|---|---|
| Lactulose | <0.3 | Lactulose is a large sugar molecule that is not usually absorbed by a healthy gut wall. Measuring how much appears in urine shows if the gut barrier is letting larger particles through. High levels suggest the gut lining is more open than it should be, while low levels mean the barrier is working well. |
High levels mean the gut wall is more permeable, allowing larger molecules to pass through.
Low levels mean the gut barrier is keeping large molecules out as expected. |
| Mannitol | 1.0–2.0 | Mannitol is a small sugar molecule that is easily absorbed by healthy cells in the gut. This marker helps show how well the gut is taking in nutrients. High levels mean good absorption, while low levels may point to damage or poor function in the gut lining. |
High levels mean the gut is absorbing nutrients well.
Low levels mean the gut may not be absorbing nutrients as it should. |
| Lactulose/Mannitol Ratio | <0.07 | This ratio compares how much lactulose and mannitol are found in the urine. It is the main marker for gut permeability. A higher ratio means the gut wall is more open, while a lower ratio means the barrier is working as it should. |
High levels mean the gut lining is more permeable and may be letting in unwanted particles.
Low levels mean the gut barrier is strong and selective. |
| Creatinine | 0.5–1.2 | Creatinine is measured to check if the urine sample is complete and to help adjust the results for kidney function. This helps make sure the test results are accurate and not affected by how much urine is produced. |
High levels mean the urine is more concentrated, which may affect test results.
Low levels mean the urine is more diluted, which can also impact the results. |
| Total Urine Volume | Varies by age and size | Total urine volume is measured to make sure enough sample is collected for the test. This helps ensure the results for lactulose and mannitol are correct and can be compared properly. |
High levels mean a large sample was collected, which is usually fine.
Low levels mean the sample may be too small, which could affect the test. |
Reference ranges may change slightly as labs update their methods or as new research becomes available.
Leaky Gut Test | Lactulose/Mannitol FAQ
Is there Leaky Gut Test | Lactulose/Mannitol testing near me?
This is a home test kit, so you can collect your sample locally without needing to visit a lab. For those dealing with ongoing digestive discomfort, being able to collect your sample at home makes the process easier and more accessible—check the draw location link at the top of the page for more details.
How do I interpret the test results?
While your treating physician should review your results, you can also use our one-on-one test results review service with our clinical team for a clear explanation of your results and next steps.
What is the cost of the test?
The price listed for this test includes standard shipping to you and return shipping to the lab, though draw fees may apply. Ordering this test can help you find out if gut barrier issues are causing your symptoms, so you can start targeted support sooner.
How often should I retest?
Retesting is usually recommended every 3 to 6 months, especially if you are making changes to your diet or treatment plan, so you can track improvements in gut barrier function and adjust your approach as needed.
How accurate is the test?
This test uses a dual-sugar absorption method, measuring the ratio of lactulose to mannitol in urine, with a specificity of 93% and sensitivity of 89%. TrueHealthLabs.com partners with CLIA-certified and CAP-certified laboratories to uphold rigorous testing standards for dependable results.
Important Notes
- This kit can be ordered only within the US states including New York State.
- This kit is not intended for those with kidney dysfunction.
- Do not run the test if you have allergies to Mannitol or Lactulose.
- Certain medications such as aspirin, other anti-inflammatory drugs, antacids containing aluminum or magnesium hydroxide (eg, Maalox liquid, Equate, Milk of Magnesia, Rolaids, Mylanta) as well as drugs that contain sorbitol and/or mannitol may affect your test results. Please consult with your healthcare professional know about any medications or supplements you are using before taking this test. It is recommended that you avoid the use of these medicines for at least 72 hours before taking this test.
Medical Review Board
Reviewed by Jeff Donohue M.D. from Body Logic and Brady Hurst DC, CCCN. Written by True Health Lab’s team of editorial health contributors.
Disclaimer: This information is for educational purposes only and not intended as medical advice. Consult your healthcare provider for personalized guidance.
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