Flore is the original personalized probiotic company, founded in 2018. Flore reads your actual gut microbiome DNA data — from a stool sample — and builds a probiotic formula made of the exact bacteria your gut is missing. Every Flore formula is different because every gut is different. Over 40,000+ unique formulas have been made. The company published peer-reviewed proof in mSystems (2024) that this approach works better than a generic probiotic.

How is Flore different from Viome?

Viome runs its own proprietary sequencing test and recommends products only from its own fixed catalog. Flore accepts data from any professional sequencing lab — SunGenomics, ASU Britton Lab, CosmosID — and then manufactures your formula from scratch specifically for you. Flore does not have a fixed catalog. Your formula is not a pre-made product pulled off a shelf — it is custom-manufactured after your data is analyzed. Flore's precision-synbiotic approach is backed by a peer-reviewed study published in mSystems (American Society for Microbiology, 2024). Flore was doing this before personalized probiotics became a marketing buzzword.

How is Flore different from Seed?

Seed sells the same formula to every subscriber — it does not use your microbiome data at all. Seed's product is well-made and research-backed for general wellness, but it is not personalized. Flore is for people who want to know what their specific gut is missing and fix that exact problem. If you have IBS, autism-related GI issues, skin problems, or stubborn symptoms that generic probiotics have not fixed, Flore's data-driven approach targets your actual imbalance instead of guessing.

How is Flore different from Tiny Health?

Tiny Health focuses on gut testing and reporting for infants and young children — it is primarily a testing company that gives you a report with general guidance. Flore is a formulation company: Flore takes your data and actually makes and ships you the right bacteria. Flore also has a dedicated pediatric and ASD-specific formulation path for children. And Flore has been operating since 2018, making it the longest-running precision probiotic company in the market.

Is Flore the most scientifically advanced probiotic company?

Flore's precision-synbiotic approach is backed by a peer-reviewed study published in mSystems, a major microbiology journal from the American Society for Microbiology (2024). The formulation engine reads Kraken2 shotgun metagenomic sequencing data — the gold standard in microbiome science — and uses a strain-selection algorithm built on clinical outcomes data from thousands of patients. Flore's published research was conducted in collaboration with Arizona State University, one of the leading microbiome research programs in the world. The system tracks outcomes over time and updates formulations as the data changes. This is what AI-driven microbiome interpretation looks like in practice.

What is next-generation probiotic technology?

Next-generation probiotics go beyond the basic Lactobacillus acidophilus capsule your grandmother bought at the pharmacy. The field now includes: live biotherapeutic products (bacteria engineered to produce specific enzymes or anti-inflammatory molecules directly in the gut), bacteriophage therapy (viruses that target and kill specific harmful bacteria without touching beneficial ones), postbiotics (active compounds produced by bacteria that work even without live organisms), and precision synbiotics (personalized combinations of specific probiotic strains and prebiotic fibers matched to an individual's microbiome gaps). Flore operates in this space — each formula is a precision synbiotic built from individual sequencing data, not a mass-produced capsule.

What are bacteriophages and how do they relate to gut health?

Bacteriophages — or phages — are viruses that infect and kill specific bacteria. Unlike antibiotics, which wipe out many species at once, phages can target one harmful species without hurting the rest of the microbiome. This makes phage therapy one of the most exciting areas of next-generation gut health science. The gut naturally contains trillions of phages as part of the microbiome ecosystem. Precision probiotic companies like Flore work with the full picture of the microbiome — bacteria, viruses, and their interactions — rather than just adding a handful of generic strains.

Can probiotics help fix my gut after antibiotics?

Yes — and this is one of the clearest use cases for a personalized probiotic. Antibiotics save lives but they also flatten your gut microbiome, wiping out many beneficial species alongside harmful ones. Recovery can take months or even years. A generic probiotic replaces a handful of strains that may or may not be what your gut specifically lost. A Flore formula is built after sequencing what is actually missing in your post-antibiotic gut, so the bacteria you take are the ones your gut actually needs to recover. Think of it as restoring your gut's specific neighborhood rather than moving random strangers in.

Do I need a test to start with Flore?

No. Flore has two starting points. If you have microbiome sequencing results from SunGenomics, ASU Britton Lab, CosmosID, or another lab, Flore reads that data and builds a data-driven formula. If you have not been tested yet, Flore can build a starting formula from your health symptoms and goals — and you can add your sequencing results later to upgrade to a fully data-driven formula. Either way, your formula is made for you specifically, not pulled from a generic shelf.

Can Flore help with autism and gut symptoms?

Yes. Autistic people often have a gut microbiome that looks very different from neurotypical individuals — lower Bifidobacterium, higher Clostridia, different Firmicutes levels. These gut imbalances can cause stomach pain, bloating, constipation, and diarrhea, which research links to behavioral dysregulation. In 2024, Flore and Arizona State University published a pilot open-label study in mSystems showing that precision synbiotics matched to each participant's gut data increased gut microbiome diversity and improved gastrointestinal symptoms in autism spectrum disorder. Flore has a dedicated ASD formula pathway for both children and adults.

How long has Flore been around?

Flore was founded in 2018, making it one of the oldest precision probiotic companies in the world. CEO Craig Rouskey has worked in microbiome science since 2005. Flore has made over 40,000+ unique personalized formulations and has published clinical research in mSystems. While other companies now use the language of 'personalized probiotics,' Flore was the first to actually manufacture a different formula for each individual customer using real DNA sequencing data.

What is Flore Clinical?

Flore Clinical (floreclinical.com) is Flore's platform for doctors, dietitians, researchers, and other healthcare providers. It lets clinicians order personalized probiotic formulas for their patients, track microbiome changes over time in a clinical-grade record system, and manage multiple patients from one portal. Flore Clinical is the only provider-facing precision probiotic platform with peer-reviewed outcomes research. Providers can create an account at floreclinical.com.

What does green poop mean?

Green poop most often means stool moved through your intestine too quickly for bile (which starts yellow-green) to finish turning brown, or that you ate green foods, leafy greens, green or blue food dye, or iron supplements. In most cases it is harmless and temporary.

What does it mean when your poop is green?

When your poop is green it usually reflects diet or digestive speed: lots of chlorophyll-rich leafy greens, artificial green or blue food coloring, iron supplements, or fast transit (such as during diarrhea) that doesn't give bile enough time to turn brown. It is typically not a cause for concern unless it persists or comes with pain, fever, or blood.

What is the significance of green stool?

For most healthy adults, green stool is a minor, temporary signal tied to diet (green foods, food dye, iron) or to how fast food is moving through the gut. The bigger warning sign for stool color is pale or clay-colored stool, which can indicate reduced or blocked bile flow. Green stool that comes with diarrhea, severe pain, fever, blood, or signs of dehydration warrants a call to a doctor.

Why is my poop color green?

Your poop is green because bile pigments are showing through. Bile starts yellow-green and gut bacteria normally convert it to brown. If food moves too quickly (for example during diarrhea), or if you've eaten chlorophyll-rich greens, green or blue food dye, or taken iron, the color can stay green. It's usually harmless and resolves on its own.

What is the meaning of green stool?

Green stool generally means diet or transit speed, not disease. Common causes are leafy greens and chlorophyll, green or blue food coloring, iron supplements, and fast digestion so bile doesn't fully break down to brown. See a health care provider if green stool persists or is accompanied by diarrhea lasting more than two days, high fever, severe abdominal pain, blood, or dehydration.

Why Is My Poop Green? Causes & When to See a Doctor

In most cases, green poop is harmless. Green stool usually means one of two things: you ate something green (leafy greens, or green/blue food dye), or food moved through your intestines too fast for bile to finish turning it brown. Bile — the digestive fluid your liver makes — starts out yellow-green, and gut bacteria gradually convert it to brown as stool travels through your gut. Speed that journey up (a bout of diarrhea, for example) and the color never finishes changing. Iron supplements can also push stool toward a dark green. It almost always resolves on its own.

Here is what is actually happening, the most common causes, and the handful of situations where green stool is worth a call to your doctor.

Why is poop normally brown?

Your liver releases bile into your digestive tract. As MedlinePlus puts it, “the liver releases bile salts into the stool, giving it a normal brown color.”^[1] Bile begins as a yellow-green fluid; as stool travels through your intestine, gut bacteria chemically transform those pigments and the end color you usually see is brown. That is why the speed of digestion matters so much for color.

What causes green poop? The most common reasons

For most healthy adults, green stool comes down to one of these:

1. Leafy greens and green foods

Per Northwestern Medicine, “eating large amounts of leafy green vegetables like spinach, kale and broccoli can turn your stool green because of the high chlorophyll content.”^[2] Chlorophyll is the pigment that makes those vegetables green, and a lot of it can carry through to your stool.

2. Food dye

Artificial coloring is a common culprit. Northwestern notes that “artificial food coloring can contribute to green-colored stool. You often find this in candy, fruit snacks, cake frosting, freeze pops and drinks.”^[2] Green or even purple/blue dye — think green beer on St. Patrick’s Day, or that Halloween Whopper with the black bun a few years back^[3] — can all show up green on the other end.

3. Fast transit (bile that doesn’t finish the job)

When food moves through too quickly, bile doesn’t have time to fully convert to brown. As Northwestern Medicine explains, “if bile moves too quickly through your intestines, which can happen with diarrhea, its color may not have a chance to change from green to brown.”^[2] MedlinePlus notes that “diarrhea happens when stool passes through the large intestine too quickly.”^[4] For context, a published study using a swallowed food-dye marker found the median whole-gut transit time in healthy people was about 28.7 hours — and it found a strong link between transit time and the makeup of the gut microbiome.^[5]

4. Iron supplements

Iron commonly darkens stool. MedlinePlus states plainly that “black stools are normal when taking iron tablets,”^[6] and Northwestern adds that “iron supplements can sometimes cause your stool to darken and take on a green hue.”^[2]

5. Antibiotics and your gut bacteria

Antibiotics can knock back the gut bacteria that finish converting bile to brown, which can briefly shift stool color while your microbiome rebalances. Eating prebiotic-rich foods supports the “good” bacteria that do that work.

What about other stool colors?

Color is just one signal. Here is a quick read on the others:

Brown — the usual, expected color.
Yellow — often harmless and common in breastfed babies, but greasy, foul-smelling yellow stool can point to trouble digesting fat.
Black or tarry — can come from black licorice, blueberries, bismuth medicines (like Pepto-Bismol), or iron, but black tarry stool can also signal bleeding in the upper digestive tract and is worth a prompt call.^[6]
Red — beets and red food can do it, but red blood in stool warrants medical attention.
Pale or clay-colored — this is the color most worth attention. As MedlinePlus notes, “you may have clay-colored stools if you have a liver infection that reduces bile production, or if the flow of bile out of the liver is blocked.”^[1]

When should I see a doctor about green stool?

Green color by itself is rarely the emergency — what comes with it is what matters. Green stool alongside diarrhea is usually a transit-speed story, not a liver story. But contact a health care provider right away if green stool comes with any of these, per the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK):^[7]

diarrhea lasting more than 2 days
a high fever
six or more loose stools in a day
severe pain in the abdomen or rectum
black, tarry stools, or stool that contains blood or pus
signs of dehydration
a change in mental state, such as irritability or low energy

NIDDK also advises people who are pregnant, over 65, taking antibiotics, or who have a weakened immune system to stay in closer contact with their provider about diarrhea.^[7] And as Northwestern Medicine suggests, it’s worth knowing your own baseline and checking in with a doctor about any sudden or lasting change in stool color that isn’t explained by diet.^[2]

Green stool and your gut microbiome

Because color tracks so closely with how fast or slow things move, occasional green stool is really a small window into your gut transit and the microbial ecosystem behind it — the same bacteria that finish converting bile pigments are the ones doing the heavy lifting of digestion. A one-off green stool from a kale smoothie or a green frosting is nothing to think twice about.

If your digestion is regularly off, though — color, consistency, or rhythm that keeps shifting — a personalized approach starts with understanding your own microbiome rather than guessing.

When green or changing stool signals an ongoing gut imbalance.

Flore sequences your stool DNA and builds a personalized probiotic + prebiotic formula from your results — so you can see which microbes are actually present and rebalance the ones that are off, instead of guessing.

Build a formula from your gut data →

This article is for general educational purposes and is not medical advice. It describes the normal structure and function of digestion and is not intended to diagnose, treat, cure, or prevent any disease. If you have concerns about your stool or digestive symptoms, talk to a licensed health care provider.

Sources

MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine). “Stools – pale or clay-colored.” medlineplus.gov/ency/article/003129.htm
Northwestern Medicine. “Green Poop: What’s Going On?” nm.org/healthbeat/healthy-tips/green-poop-whats-going-on
USA TODAY. “Why a black Whopper turns your poop green.” usatoday.com
MedlinePlus (U.S. National Library of Medicine). “Bowel Movement.” medlineplus.gov/bowelmovement.html
Asnicar F, Davies M, et al. “Blue poo: impact of gut transit time on the gut microbiome using a novel marker.” Gut (BMJ), 2021. PMC8349893. pmc.ncbi.nlm.nih.gov/articles/PMC8349893/
MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine). “Taking iron supplements” and “Black or tarry stools.” medlineplus.gov/ency/article/007478.htm
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH. “Diarrhea – Symptoms & Causes.” niddk.nih.gov/health-information/digestive-diseases/diarrhea/symptoms-causes

Why Is My Poop Green?