Should you do a gut microbiome test?

If you’ve seen those at-home gut microbiome test kits - send off a sample of your poop, get a “gut health” report, personalised diet or supplement tips - you’re not alone. Heck, you can even get them for your pets now! But before you splash out, it's worth asking: how useful are they, really? For most people, the science says: interesting, but not very actionable. Here's a clear, evidence-based look.

What a Gut Microbiome Test Actually Measures

These kits analyse DNA from a small stool sample and make guesses about which microbes are there. But that’s just the tip of the iceberg. The gut microbiome is massively diverse, and many species are still uncharacterised - meaning most tests can only see a fraction of what’s really going on. Your gut is, in part, a dynamic ecosystem and changes depending on your diet, sleep, stress, even where you are. That makes a single snapshot of a poo sample somewhat limited (1). Plus these types of tests only really tells us about transient microbes (those which tend to pass through us) and not resident microbes (those that live in our gut full time). The gold standard for gut microbiome testing is taking a biopsy of the large intestine - and that's an invasive procedure we don't want unless we really have to. On top of that, there’s currently no agreed standard for what a 'healthy microbiome' even looks like.

Reports Often Don’t Translate Into Useful Advice

Many of the dietary or supplement recommendations companies give based on tests are generic. Think: “eat more fibre, eat more plants". Not for nothing but this is advice you could find in any nutrition blog. The reality is, even if a test shows “low” levels of a supposedly beneficial microbe, it’s very hard (or impossible) to target-boost that one microbe reliably. Interventions tend to shift the ecosystem more broadly - not tune one species up or down precisely. Moreover, several expert panels strongly discourage therapeutic counselling based on the results of consumer microbiome tests, because we really don't have the evidence to prove meaningful results yet (2).

Reliability and Consistency: Big Red Flags

There's also huge variation between test providers. Different labs, different testing methods, different reference databases = very different results. A recent study sent the same stool sample to five different commercial labs and got wildly different results - things like bacterial diversity and the abundance of specific species didn’t match up (3).

Experts have warned that these tests lack analytical validity (how reliably they measure what they claim) and clinical validity (how well those measurements actually map to meaningful health outcomes). According to an international consensus from microbiome experts, the methodology is not yet standardised, and interpretation is not reliable enough to guide personal health decisions (4). In fact, the same international working group recommended that requests for these tests be made only by qualified healthcare professionals - not sold directly to consumers as a “diagnosis tool.”

When It Might Make Sense and Why It Usually Doesn’t

There are a few scenarios where microbiome testing can be more than just a novelty:

• Research or citizen science: If you want to contribute to research or understand more about your gut for curiosity’s sake, it can be interesting.

• Clinical contexts: In very specific medical settings (e.g. certain gastrointestinal diseases), more rigorous testing may be warranted - but that’s very different from a wellness-style home kit.

However, for most healthy people aiming to 'optimise' their gut, the test will likely give limited or misleading insight, without changing what you’d actually do day to day all for a pretty price.

So What's Actually Useful for Gut Health - Without the Fancy Test?

If your goal is better gut health here are evidence-based, practical steps that are effective without spending on a microbiome test:

• Focus on a diverse, fibre-rich diet: meaning lots of whole grains, legumes, seasonal fruit and vegetables.

•  Add live fermented foods like kimchi, sauerkraut, kombucha and kefir to your diet on a regular basis.

• Avoid unnecessary antibiotic use.

• Look after lifestyle factors: like better sleep, well managed stress, and moving your body.

• If you have persistent or worrying gut symptoms (bleeding, weight changes, severe constipation or diarrhoea), speak to your GP. Clinical investigations (blood tests, stool tests, imaging) are usually far more informative than a consumer microbiome kit.

  
  

Gut microbiome tests feel futuristic and scientific - but right now, they’re more a curiosity than a diagnostic tool. The data they provide is limited, and the advice they offer often boils down to what you probably already know: eat well, sleep well, and move your body. Unless you’re part of a study or under the care of a specialist, it’s probably more useful to invest in good habits than in a one-off test.

References

1 Semmelweis University (2024). Semmelweis University: This is why microbiome tests should be treated with caution. Available at: https://semmelweis.hu/english/2024/08/semmelweis-university-this-is-why-microbiome-tests-should-be-treated-with-caution

2 Cahová M, Najmanová L. Opinion of an international panel of experts on the clinical use of microbiome testing. Cas Lek Cesk. 2025;164(2):68-72.

3 Pichon M, Bouleti C; MICMAC Study Group SFM; Hery-Arnaud G, Burucoa C; MICMAC Study Group. Heterogeneity and lack of standardisation in gut microbiome testing: a comparative assessment of French medical biology laboratories. Gut. 2025 Oct 20:gutjnl-2025-336981. doi: 10.1136/gutjnl-2025-336981.

4 Porcari S et al. International consensus statement on microbiome testing in clinical practice. Lancet Gastroenterol Hepatol. 2025 Feb;10(2):154-167. doi: 10.1016/S2468-1253(24)00311-X.