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Understanding your report

How to read your microbiome results

Follow the same path you use in the dashboard: start with Overview, examine species in Gut microbes, add context in Understand, and finish with Next steps.

Your microbiome report contains several different kinds of information. Some describe what was detected in your sample, some compare your result with other people, and others summarize scientific evidence or predicted function.

No single species, percentile, diversity score, or functional prediction tells you whether your microbiome is healthy. The most useful interpretation comes from combining several pieces of evidence and, when possible, looking at how your own microbiome changes over time. Healthy people can have very different gut microbial communities, and microbial abundances can also fluctuate substantially within the same person.125

Before you open the report

What the test measures

HelloTummy analyzes bacterial DNA in a stool sample. The lab extracts microbial DNA, copies nearly the full bacterial 16S rRNA gene, sequences those DNA fragments, and uses specialized software and reference data to identify bacteria and estimate the share of the bacterial signal assigned to each species.

This is a semi-quantitative test. It estimates relative amounts—how the detected bacterial signal is divided among species. That makes it useful for identifying which species dominate a sample and for comparing community patterns across samples collected under similar conditions. It does not count the absolute number of bacterial cells or measure their concentration in your gut.34

DNA extraction, amplification, sequencing, and identification can affect species differently. Use the percentages as careful estimates of community composition, not exact cell counts.46

1

Overview

Start with the whole sample

Confirm the Sample, Collected, and Result ready details at the top. Then scan the three community cards: Overall diversity, Species richness, and Community balance.

Continue to Microbial roles in your sample, the report's main findings, and Most abundant gut microbes. These views help you see whether abundance is spread broadly or concentrated in a few species. A highly abundant organism has more opportunity to influence the measured community, so abundance helps you decide what to examine first. It does not establish importance by itself; role, evidence, and the rest of the community still matter.

A substantial abundance combined with an unusual comparison is often more informative than either number alone. For example, 10% abundance at the 98th percentile generally deserves more attention than 0.03% abundance at the same percentile.

2

Gut microbes

Read species results in context

Open the Gut microbes screen to see every reported species. The table answers four different questions:

Species
What was detected, its plain-language classification, and which biological evidence to review.
Your abundance
What share of the detected bacterial signal was assigned to this species, helping you spot dominant organisms and large shifts.
Where you stand
Your percentile among current users who also had this species detected, helping flag an unusual result for review.
How common
The share of users with the species in their latest released sample, showing whether detection is common or uncommon.

Relative abundance is compositional

All species percentages share the same 100%. If one group grows while another stays unchanged, the unchanged group becomes a smaller percentage of the total. This matters when comparing samples: read a percentage shift as a change in the species' share of the measured community, not proof that its cell count rose or fell.3

A species can change in percentage even if its actual number of cells did not change.

Be careful with tiny values. A change from 0.05% to 0.10% is a doubling, but it is only 0.05 percentage points. A change from 5% to 10% is also a doubling and represents a much larger shift in the measured community.

Percentile and prevalence answer different questions

The comparison line shows the typical abundance range among users who have that species. The orange marker is your sample. A result below the 20th percentile is labeled Low, the 20th–80th percentile is Typical, and above the 80th is High. These population comparisons help you prioritize unusual findings for a closer look; they are not clinical reference ranges.

Prevalence asks how many users have the species at all. It helps distinguish a relatively rare finding from a familiar feature of the population. A species can be uncommon but high among the people who have it, or common but low among carriers. Use its role and evidence to decide what that context may mean.

Expand a species result or row

In the Gut microbes screen, use the chevron in the Report column to expand a species result or row. The expanded area shows your abundance over time and four population measures:

Latest-sample prevalence
How many users have it in their latest released sample.
First-sample prevalence
How many users had it in their earliest released result.
Ever detected
How many users had it in at least one released sample.
Persistence
Among repeat users who have had it, how consistently it remained detectable.

Together, these measures show whether a species is widespread, persistent, or occasional, helping you distinguish a stable personal pattern from a one-time detection.

Use View report when available to read the species-specific evidence, limitations, and research sources. A high or low comparison becomes more meaningful only when the biological evidence supports that interpretation.

3

Understand · Community structure

Describe the shape of the community

Open Understand, then Community structure. Overall diversity combines aspects of variety and balance. Species richness counts how many species were detected. Community balance describes how evenly abundance is shared instead of being dominated by a few species.

The community concentration panel shows how much of the sample is accounted for by the five most abundant microbes. Use these views together: two samples can contain the same number of species but have very different balance and concentration.

In many gut communities, greater diversity and better balance can be useful because more organisms can occupy ecological niches, compete for nutrients that might otherwise support invading pathogens, and provide overlapping metabolic capabilities. That overlap may help the community maintain important functions or recover after a disturbance such as a major diet change or antibiotics.1314

Higher diversity is not automatically healthier, however. In a deliberately simple example, a gut could be highly diverse while containing only pathogens. The high diversity would not make that community healthy. Diversity describes ecological capacity; which organisms are present and what is known about them determine how that capacity should be interpreted.2

Understand · Microbial roles

Use classifications as guides, not verdicts

HelloTummy uses the labels Beneficial, Neutral, Potentially Harmful, and Harmful because they are easier to understand at a glance. Scientists commonly use Mutualist, Commensal, Pathobiont, and Pathogen for the same categories.

Plain-language labelScientific termHow to read it
BeneficialMutualistOften associated with helpful activity in the gut, depending on amount and context.
NeutralCommensalA common gut resident without a consistently helpful or harmful effect on its own.
Potentially HarmfulPathobiontUsually present without causing problems, but may be concerning at higher levels or in certain settings.
HarmfulPathogenMore consistently associated with harmful effects, although detection alone does not mean illness.

Context can change the meaning

Amount, diet, neighboring microbes, the host environment, and the particular strain can all matter. Members of the same named species can carry different genes and capabilities.6 Not Categorized means current research does not support a clear role, so rely more on abundance, comparison data, and the available species evidence than on a simple label.

Evidence strength matters

Strong support means several good-quality sources point in a similar direction. Moderate support means useful evidence exists with important limits. Limited support means evidence is early, mixed, indirect, or based on fewer studies. These levels help you decide how confidently to interpret a finding and whether it is better treated as a pattern to watch.

Understand · Functional potential

What might this community be capable of?

HelloTummy uses specialized software to predict bacterial genes and pathways from the organisms detected by 16S sequencing. The software uses relationships between detected bacteria and sequenced reference genomes to estimate which functions may be represented in the community.7

Predictions can reveal potential community-wide patterns that are easy to miss when reading one species at a time. They are most useful for forming a broader picture and deciding what to track across samples. Because they are not directly measured, they do not show whether genes were active, how quickly a pathway was operating, how much metabolite was produced, or what concentration was present in stool or blood.7

Give a prediction more weight when it is clearly unusual, several organisms contribute to it, it agrees with the species results, and the same pattern repeats across samples. Use the Supportive, Context-dependent, and Watch groupings as reading aids—not as clinical cutoffs.

Understand · Over time

Look for repeated patterns

One sample is a snapshot. Repeat samples help establish your personal baseline and show whether a pattern is sustained. A sequence such as 2% → 7% → 2% may be temporary; 2% → 7% → 8% → 7% looks more sustained and may deserve a closer review.5

Consider what was happening around each collection date, including antibiotics, a major diet change, gastrointestinal illness, diarrhea or constipation, travel, and major routine changes. These events can help you form a reasonable hypothesis and choose when to collect a comparable follow-up sample, although they do not prove what caused a microbial change.891011

A low-abundance organism can move above and below the detection threshold. “Not detected” means the test did not report enough signal in that sample; repeated detection across samples is more useful for identifying a persistent community member than one detected/not-detected change.5

4

Next steps

Turn context into a practical review

Before acting on a finding

  1. Check whether it is present at a meaningful abundance.
  2. Use Where you stand to see whether that abundance is unusual.
  3. Use How common to understand prevalence.
  4. Open the species report for evidence, limitations, and sources.
  5. Look for other species or predicted functions that support or contradict it.
  6. Compare prior samples and recall the collection context.

The Next steps tab shows personalized ideas only when they pass approved evidence and result-specific checks. General guidance is labeled separately. Neither replaces medical advice.

Download your data

Return to the Dashboard and choose Download Your Data for an Excel workbook or AI-ready JSON file. The export contains all released samples, detailed abundance and comparison data, functional predictions, definitions, and analysis notes.

The download provides more detail, not more diagnostic certainty. Protect it because optional fields can contain personal test, questionnaire, and collection-date information.

What this report cannot tell you

The report does not directly measure absolute bacterial cell counts, every organism or strain, gene activity, metabolite production, metabolite concentrations, every intestinal location, why a change occurred, or whether a microbe caused a symptom or health condition. What it can do is organize detected species, population comparisons, ecological structure, research context, and change over time into patterns you can understand and track. HelloTummy results are for wellness education and personal tracking; they are not intended to diagnose, treat, prevent, or assess disease.

Research basisReferencesShow sources
  1. 1.Human Microbiome Project Consortium. Structure, function and diversity of the healthy human microbiome. Nature 486, 207–214 (2012).
  2. 2.Van Hul, M. et al. What defines a healthy gut microbiome? Gut 73, 1893–1908 (2024).
  3. 3.Morton, J. T. et al. Establishing microbial composition measurement standards with reference frames. Nature Communications 10, 2719 (2019).
  4. 4.McLaren, M. R., Willis, A. D. & Callahan, B. J. Consistent and correctable bias in metagenomic sequencing experiments. eLife 8, e46923 (2019).
  5. 5.Vandeputte, D. et al. Temporal variability in quantitative human gut microbiome profiles and implications for clinical research. Nature Communications 12, 6740 (2021).
  6. 6.Greenblum, S., Carr, R. & Borenstein, E. Extensive strain-level copy-number variation across human gut microbiome species. Cell 160, 583–594 (2015).
  7. 7.Douglas, G. M. et al. PICRUSt2 for prediction of metagenome functions. Nature Biotechnology 38, 685–688 (2020).
  8. 8.Vandeputte, D. et al. Stool consistency is strongly associated with gut microbiota richness and composition, enterotypes and bacterial growth rates. Gut 65, 57–62 (2016).
  9. 9.Procházková, N. et al. Gut physiology and environment explain variations in human gut microbiome composition and metabolism. Nature Microbiology (2024).
  10. 10.David, L. A. et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature 505, 559–563 (2014).
  11. 11.Palleja, A. et al. Recovery of gut microbiota of healthy adults following antibiotic exposure. Nature Microbiology 3, 1255–1265 (2018).
  12. 12.Shalon, D. et al. Profiling the human intestinal environment under physiological conditions. Nature 617, 581–591 (2023).
  13. 13.Spragge, F. et al. Microbiome diversity protects against pathogens by nutrient blocking. Science 382, eadj3502 (2023).
  14. 14.Tian, L. et al. Deciphering functional redundancy in the human microbiome. Nature Communications 11, 6217 (2020).
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