How to Read Your Microbiome Test Results

At a Glance

The First Thing to Understand

Before you look at a single number on your microbiome test report, understand this: there is no single “normal” or “ideal” microbiome. The Human Microbiome Project, which sequenced the gut microbiomes of thousands of healthy individuals, found enormous variation. A healthy Hadza tribesperson in Tanzania has a dramatically different microbiome from a healthy software engineer in Berlin — and both are “normal” [1].

What matters is not matching a specific profile. What matters is functional patterns — whether your microbial ecosystem has the diversity, the key players, and the metabolic capacity to support immune function, barrier integrity, and anti-inflammatory signaling.

Let me walk you through how to read your results with that framework.

The Major Markers on Your Report

Microbial Diversity

What it measures: How many different species are present and how evenly distributed they are.

Why it matters: Higher diversity consistently correlates with better health outcomes across hundreds of studies. Low diversity is associated with inflammatory bowel disease, obesity, type 2 diabetes, allergies, autoimmune conditions, and — particularly relevant to my patient population — chronic infection and antibiotic-related disruption.

How it is reported: Typically as alpha diversity indices — Shannon diversity index (accounts for both richness and evenness) and/or species richness (total number of species detected).

What to look for: Low diversity compared to the reference population is a red flag, particularly if the patient has a history of antibiotic use, chronic illness, or restricted diet.

Phylum-Level Composition

The two dominant phyla in the human gut are Bacteroidetes and Firmicutes, which together typically comprise 80-90% of the gut microbiome.

Bacteroidetes-to-Firmicutes ratio: While this ratio has been somewhat oversimplified in popular media, it does carry clinical relevance. An elevated Firmicutes-to-Bacteroidetes ratio is consistently associated with obesity, metabolic syndrome, and inflammatory states. However, this is a broad pattern, not a diagnostic criterion.

Proteobacteria: This phylum includes many pathobionts (potentially pathogenic organisms). Elevated Proteobacteria — particularly Enterobacteriaceae family members — is a marker of dysbiosis and gut inflammation. It is sometimes called the “microbial signature of disease.”

Keystone Species

These are specific organisms whose presence or absence has outsized importance for gut ecosystem function:

Akkermansia muciniphila:

• Maintains the mucus layer lining the intestinal wall
• Levels correlate inversely with inflammation, obesity, and metabolic dysfunction
• Low Akkermansia is one of the most clinically actionable findings on a microbiome test
• Supported by clinical trial data (Depommier et al., 2019)

Faecalibacterium prausnitzii:

• The most abundant butyrate producer in the human gut
• Anti-inflammatory — produces metabolites that suppress NF-kB signaling
• Low levels are consistently found in Crohn’s disease, ulcerative colitis, and chronic inflammatory states

Bifidobacterium species:

• Critical for immune regulation and barrier function
• Depleted by antibiotics — often severely
• Low levels correlate with increased intestinal permeability (“leaky gut”)

Roseburia species:

• Major butyrate producer
• Supports epithelial cell energy and barrier integrity

Pathobionts and Overgrowth Markers

These organisms are normal residents at low levels but become problematic when overgrown:

• Klebsiella pneumoniae: Associated with gut inflammation and autoimmune triggering (molecular mimicry with HLA-B27)
• Enterococcus: Elevated levels suggest dysbiosis and reduced colonization resistance
• Citrobacter: Potential pathobiont associated with gut inflammation
• Candida species: Fungal overgrowth marker (also measured on OAT testing)
• Clostridium difficile: Toxin-producing pathogen that thrives after antibiotic disruption

Metabolic Function Markers

Some advanced panels estimate the metabolic output of the microbiome:

• Short-chain fatty acid (SCFA) production potential: Butyrate, propionate, and acetate are fermentation products that feed colonocytes, maintain barrier function, and regulate immune responses. Low SCFA production capacity suggests insufficient fiber-fermenting bacteria.
• Beta-glucuronidase: High levels indicate that the microbiome is deconjugating estrogens and toxins, effectively recycling them back into circulation. This has implications for estrogen-related conditions and detoxification.

How to Read Your Results: A Step-by-Step Approach

Step 1: Check Diversity First

Is your overall diversity low, normal, or high compared to the reference population? Low diversity is the single most consistent marker of an unhealthy gut ecosystem.

Step 2: Identify Missing Keystone Species

Are Akkermansia, Faecalibacterium, Bifidobacterium, and Roseburia present? If multiple keystone species are depleted, the gut’s anti-inflammatory and barrier-maintenance functions are compromised.

Step 3: Check for Overgrowth

Are any pathobionts elevated? Look particularly at Proteobacteria family members and Candida. Overgrowth of these organisms in the setting of depleted keystone species is the classic dysbiosis pattern.

Step 4: Assess Metabolic Function

Is SCFA production capacity adequate? Is beta-glucuronidase elevated? These functional markers tell you what the microbiome is doing, not just what is there.

Step 5: Contextualize

Before making treatment decisions, consider:

• Recent antibiotic use (how long ago? how many courses?)
• Current diet (fiber intake directly influences results)
• Current medications (proton pump inhibitors, NSAIDs, and other drugs alter the microbiome)
• Clinical symptoms (do the dysbiosis patterns match the symptom profile?)

The Evidence

What We Know (Human Data)

• The Human Microbiome Project established reference ranges and normal variation for gut microbial communities [1]
• Depommier et al. (2019) demonstrated that Akkermansia muciniphila supplementation improved metabolic parameters in overweight humans — the first RCT supporting targeted microbiome restoration [2]
• Multiple studies in IBD have established Faecalibacterium prausnitzii depletion as a reliable biomarker of disease activity
• The Hopkins Lyme group identified distinct microbiome signatures in post-treatment Lyme disease patients

What I See in Practice

In our hospital, I order microbiome testing for patients with:

• Gastrointestinal symptoms persisting after infection treatment
• History of prolonged or repeated antibiotic courses
• Chronic fatigue with suspected gut-immune axis involvement
• Autoimmune conditions (microbiome profiling guides immune modulation)

The most common findings in chronic Lyme patients:

• Severely depleted diversity (often from multiple antibiotic courses)
• Low or absent Bifidobacterium and Lactobacillus species
• Elevated Candida and Clostridium markers
• Reduced butyrate production capacity
• Increased intestinal permeability markers

What I tell my patients: your microbiome test is a snapshot of the ecosystem in your gut. After chronic illness and antibiotics, that ecosystem is often devastated — like a forest after a fire. The test tells us what needs replanting and what weeds need pulling.

Practical Application

Choosing a Testing Platform

For most clinical purposes, I recommend the GI-MAP for its quantitative pathogen and commensal data, supplemented by a sequencing-based test if diversity assessment is the priority.

Acting on Your Results

Low diversity: Increase dietary fiber diversity (aim for 30+ different plant foods per week), consider prebiotic supplementation (partially hydrolyzed guar gum, FOS, GOS), and avoid unnecessary antibiotics.

Depleted keystone species: Targeted probiotic supplementation (strain-specific), prebiotic feeding of target species, and dietary modification to support their growth.

Pathobiont overgrowth: Botanical antimicrobials (berberine, oregano oil, garlic), targeted antibiotics if indicated, and strategies to increase colonization resistance (probiotics, SCFAs).

Elevated beta-glucuronidase: Calcium-d-glucarate supplementation, increased fiber intake, and investigation of estrogen metabolism.

Safety and Considerations

Stool testing is non-invasive and carries no physical risk. The main considerations:

• Over-interpretation: Not every “out of range” organism needs treatment. Many microbiome variations are normal and clinically insignificant.
• Test-retest variability: Microbiome composition fluctuates with diet, stress, and time of day. A single test is a snapshot.
• Actionability gap: The field of microbiome restoration is advancing rapidly, but we do not yet have targeted interventions for every finding. Some results are informative but not yet actionable.
• Cost: 300-500 USD, variable insurance coverage.

The Bottom Line

Reading your microbiome test results requires understanding patterns, not memorizing species names. High diversity is good. Keystone species (Akkermansia, Faecalibacterium, Bifidobacterium) should be present. Pathobionts should be kept in check. Metabolic function (SCFA production, beta-glucuronidase) tells you what the ecosystem is actually doing. Interpretation must always account for your clinical history — particularly antibiotic use, diet, and underlying conditions. The goal is not a perfect microbiome. The goal is a functional ecosystem that supports immune regulation, barrier integrity, and anti-inflammatory signaling.

References

1. Human Microbiome Project Consortium. Structure, function and diversity of the healthy human microbiome. Nature. 2012;486(7402):207-214. PMID: 22699609.
2. Depommier C, et al. Supplementation with Akkermansia muciniphila in overweight and obese human volunteers: a proof-of-concept exploratory study. Nature Medicine. 2019;25(7):1096-1103. PMID: 31263284.
3. Lloyd-Price J, et al. Multi-omics of the gut microbial ecosystem in inflammatory bowel diseases. Nature. 2019;569(7758):655-662. PMID: 31142855.