An at-home gut microbiome test works by having you collect a tiny stool (poop) sample, mailing it to a lab, and sequencing the DNA of the microbes in that sample to identify which bacteria live in your gut and roughly in what proportions. Most consumer tests use either 16S rRNA gene sequencing (which identifies bacteria, often to the genus level) or shotgun metagenomic sequencing (which reads all the DNA and can resolve more detail, including function). The result is a snapshot of your gut community — useful for personalization, but one that shifts over time, so it’s best read as a starting point rather than a fixed diagnosis. Here’s how the process works, step by step, and what the science says about what these tests can and can’t tell you.
What is the gut microbiome?
Your microbiome is “the community of microorganisms (such as fungi, bacteria and viruses) that exists in a particular environment” — in this case, your gastrointestinal tract.[1] These microbes aren’t just passengers: as the NIH’s National Human Genome Research Institute notes, “gut bacteria aid digestion,” and the community as a whole helps provide “colonization resistance” by occupying space that would otherwise be available to harmful microbes.[1] A microbiome test is simply a way to take inventory of who is living there.
How does an at-home microbiome test work, step by step?
The mechanics are more straightforward than the science behind them. In practice, almost every at-home gut test follows the same four steps:
- You collect a small stool sample at home. Stool is the standard material for gut testing because “stool samples are often used when assessing the gut microbiome as a non-invasive approach.”[2] A swab or scoop captures enough material to read the bacteria that have passed through your gut.
- You mail the sample to a lab in the kit’s prepaid packaging, usually with a preservative so the sample is stable in transit.
- The lab extracts DNA from the sample and sequences it. This is the core of the test — reading the genetic material of the microbes present (more on the two main methods below).
- You get a report that translates the raw sequencing data into a readable summary: which bacteria were detected, their relative abundance, and often diversity scores or comparisons to a reference population.
16S rRNA sequencing vs. shotgun metagenomic sequencing
The detail you get out of a microbiome test depends mostly on which sequencing method the lab uses. There are two common approaches.
16S rRNA gene sequencing
This is the most widely used method for consumer tests. “16S rRNA sequencing has been widely used to characterize the bacterial community, which utilizes PCR to target and amplify portions of the hypervariable regions (V1–V9) of the bacterial 16S ribosomal RNA subunit gene.”[2] In plain terms, it reads one “barcode” gene that’s present in bacteria, which is enough to tell different bacteria apart. Its trade-off is resolution: traditional analysis methods “only can provide genus or above level taxonomic information,” although newer methods like DADA2 “can perform species-level analysis.”[2]
Shotgun metagenomic sequencing
Shotgun sequencing reads everything, not just one marker gene. Metagenomics is “the study of the structure and function of entire nucleotide sequences isolated and analyzed from all the organisms (typically microbes) in a bulk sample.”[3] Because it isn’t limited to a single primer, “shotgun metagenomic sequencing is capable of random sequencing the sample’s entire metagenome without a specific primer, which alleviates biases from primer choices.”[2] The payoff is more detail: compared with marker-gene profiling, “shotgun metagenomic sequencing adds a detailed layer to the taxonomic characterization of the community by providing information on the gene composition and the functional capacity of the gut microbiome.”[2] In other words, it can get closer to species and strain level and start to describe what your microbes can do, not just who they are.
What does an at-home microbiome test show?
A typical report tells you which bacterial groups were detected and their relative abundance — the proportions of the community, not a head-count. Depending on the method, it may resolve those groups to the genus or species level, and shotgun-based tests may add a layer of functional/metabolic information.[2] Many reports also include a diversity measure and compare your sample against a reference set. What it generally does not show is a clean “diagnosis”: it’s a description of your gut community at one moment in time.
Are at-home microbiome tests accurate or worth it?
This is where honesty matters. The sequencing itself can be quite precise, but interpreting a single snapshot is genuinely hard — because the microbiome is a moving target. As a 2025 review puts it, “microbiome composition is influenced by a multitude of factors, including diet, medication, time of day, and environmental exposures,” and “these dynamics not only vary between individuals but also fluctuate within the same individual under different conditions.”[4] So two samples from the same person on different days can look different.
The same review cautions that direct-to-consumer tests “often fail to account for the microbiome’s variability,” and that such tests “lack standardization and are prone to misinterpretation by consumers.”[4] The practical takeaway: an at-home microbiome test is a useful starting point and personalization input, not a stand-alone medical diagnosis. Treat the results as one piece of information, sample under consistent conditions when you can, and bring anything concerning to a licensed clinician.
How a microbiome test turns into a personalized probiotic
On its own, a microbiome report is just data. Its real value shows up when it’s used to act — choosing the specific bacterial strains and prebiotic fibers most relevant to the gaps and patterns in your community, rather than buying a generic, one-size-fits-all probiotic and hoping it matches. That’s the difference between a personalized probiotic and an off-the-shelf one.
This is exactly what Flore (formerly Sun Genomics) is built around: Flore sequences your stool DNA and then manufactures a personalized probiotic-plus-prebiotic formula from your results, matching strains and fibers to your individual microbiome instead of guessing. If you’d like to map your gut and turn the results into a formula, you can start with the Flore Test to Treat or learn more about the personalized probiotic itself.
This article is for general educational purposes and is not medical advice. It describes the normal structure and function of the gut microbiome and how microbiome sequencing works, and is not intended to diagnose, treat, cure, or prevent any disease. Microbiome test results are not a stand-alone diagnosis — talk to a licensed health care provider about your individual needs.
Sources
- “Microbiome.” Talking Glossary of Genomic and Genetic Terms, National Human Genome Research Institute (NHGRI), NIH. genome.gov/genetics-glossary/Microbiome
- “An Introduction to Next Generation Sequencing Bioinformatic Analysis in Gut Microbiome Studies.” PMC8066849. pmc.ncbi.nlm.nih.gov/articles/PMC8066849/
- “Metagenomics.” Talking Glossary of Genomic and Genetic Terms, National Human Genome Research Institute (NHGRI), NIH. genome.gov/genetics-glossary/Metagenomics
- “Navigating microbiome variability: implications for research, diagnostics, and direct-to-consumer testing.” PMC12018463, 2025. pmc.ncbi.nlm.nih.gov/articles/PMC12018463/
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