Leaky gut test

For ongoing digestive problems, brain fog, low energy, or unexplained skin issues. A condition that occurs when the lining of the gut becomes permeable.

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What is a leaky gut test?

The gut lining normally acts as a barrier, allowing nutrients to pass through while keeping larger, potentially harmful particles - like toxins and bacteria - out of the bloodstream. When this barrier becomes “leaky,” it can lead to systemic inflammation and a wide range of health issues.

In leaky gut syndrome - the tight junctions in your gut lining weaken. When these junctions loosen, it can result in foreign particles escaping into the bloodstream, triggering inflammation and immune reactions throughout the body.

This condition is known as increased intestinal permeability, often referred to as leaky gut syndrome. It’s not a disease itself, but rather a sign that something deeper may be affecting your gut health.

Our test for leaky gut uses two specific sugar molecules mannitol and lactulose to measure how much passes through your intestinal lining. Here’s how it works:

· Mannitol is a small molecule that is usually absorbed easily in a healthy gut.

· Lactulose, being larger, should not cross the gut barrier unless it’s compromised.


This method is widely accepted for assessing intestinal permeability and provides valuable insight for diagnosing leaky gut syndrome.

How it works

You will drink a solution containing both sugars, and over the next 3 hours, you will collect all urine passed.

The lab will then measure how much of each sugar appears in your urine.

If elevated levels of lactulose are present, it suggests the gut barrier is more porous than it should be.

Download the information leaflet

Preparing for your test

Before you test, there are some things we ask you to do, to ensure safety and accurate results. This includes stopping certain medication and fasting for a short period.

Please read our patient information leaflet for full details.

1 week before your test

Avoid non-steroidal anti-inflammatory drugs (NSAIDs) (Ibuprofen, aspirin, and naproxen).

Stop any laxatives

Refrain from endurance exercise lasting more than 45 minutes

2 days before your test

Discontinue Loperamide (Imodium)

The day before your test

You must follow the ‘white food diet’ which  consists of only the following foods and drinks:    

• Plain white bread

•  Plain white rice

•  White potatoes (no skin)

•  Baked/grilled chicken, turkey, lean beef,  lean pork, white fish (no oily fish)

•  Maximum of 2 eggs

•  Water (non-carbonated)

•  Non-flavoured black coffee (no milk)

•  Non-flavoured black tea (no milk and no  herbal teas)

•  1 tbsp butter/margarine/oil

•  Salt to flavour food  

Do not eat or drink anything else, eating  prohibited foods could give false results for the test.

Do not chew gum in the 24 hours before testing.

Getting your test results

If the test shows increased permeability, it’s often a sign of something deeper, not a diagnosis on its own, but an indicator worth exploring.

Leaky gut can be linked to a number of underlying issues such as:

· Gut dysbiosis (imbalanced gut microbiome)

· Food sensitivities

· Chronic infections

· Inflammatory bowel diseases

· Coeliac disease or gluten sensitivity

· Prolonged stress or medication overuse

It’s a good idea to speak with your doctor or a registered dietitian to determine the next steps. A healthcare professional can help interpret the results and build a personalised plan to repair and support your gut.

Paying for your test

Self-paying: If you are paying for this test yourself and not through insurance, the cost will be £350

This cost includes cost of the test kit, lab analysis and the final report.

Insurance coverage

If you have private medical insurance, most companies can cover this for you.

After the Test (Post-Procedure Care)

After the test you can restart any medication and continue your everyday activities as usual.

Your results will be sent to a specialist for investigation, and you will get your detailed results at your next appointment with your consultant, who will discuss the outcome and all treatment solutions.

Frequently Asked Questions

Can I do this test whilst pregnant?

Yes, this is a safe test with no associated risks. However, patients should inform their GP/doctor to ensure they are happy to continue.

Do I need to fast before the test?

Yes. You need to fast for at least 12 hours before the test. You should also follow a strict low-fermentable diet on the day before the test.

What foods can I eat on the day before the test?

- Plain white bread

- Plain white rice

- Plain white potatoes (no skin)

- Baked or grilled white meat or fish (no oily fish, no skin)

- Firm or extra firm tofu

- Eggs (maximum of two)

- Water

- Non-flavoured black coffee or black tea (no milk)

- Only salt may be used to flavour your food

- A little butter, oil or margarine is permitted (1tbsp)

No other foods or drinks are allowed.

How long until I get the results?

Once the kit arrives back to our lab the results will typically be available within 3 working days.

Is the test straight forward to complete on your own at home?

Yes, the test is very simple to complete with clear instructions. Ensure you are comfortable giving breath samples before starting as doing this incorrectly will result in inconclusive results.

What is the difference between SIBO Lactulose and SIBO Glucose?

Lactulose is a synthetic sugar which is not absorbed in the small intestine. This means it can detect SIBO throughout the entire small intestine and is more sensitive than glucose. However, it is more likely to give a false positive result than glucose due to this increased sensitivity. It does not cause blood sugar to rise since it isn’t absorbed.

Glucose is well absorbed early in the small intestine, meaning it can miss SIBO present in the lower part of the small intestine and give a false negative result. It is however more specific than lactulose so can be more certain a positive result is a true positive.

Which test is best out of the two? Lactulose is usually recommended due to its higher sensitivity unless the GI tract is altered due to past abdominal surgery.

If I self-refer and I am positive for SIBO – how do I go about getting the treatment for SIBO?

If you are positive for SIBO, we have a list of consultants that we work with that we would recommend for you to contact to receive treatment for SIBO.

I have had gastric surgery (gastric bypass, sleeve gastrectomy, gastric banding, or gastric balloon, etc) can I have this test done?

Yes, glucose substrate is recommended due to altered anatomy of the GI trace.