Dysbiosis: What You Need to Know
What dysbiosis means
Dysbiosis is a word for an imbalance in a community of microbes living in or on the body. Cleveland Clinic describes a balanced microbiome as one with a healthy variety of bacteria, viruses and fungi where no single type dominates. Dysbiosis is when that mix shifts and the community works differently. People most often use the word for the gut, but it can also apply to the mouth, skin and urinary or genital tract.
The term sounds precise, but scientists still argue about it. A 2017 analysis of how researchers use the word found many different definitions and warned that it is often used as if it proves cause, when it only describes a pattern. A 2020 critique in Microbial Biotechnology pointed out that many studies linking dysbiosis to disease are small, and that most microbiome research is still descriptive. In short, there is no single lab cutoff that says “you have dysbiosis.”
This article is general information, not medical advice. If you have ongoing gut symptoms, a doctor is the right person to sort out the cause.
Why it matters for gut health
Some imbalances are clearly harmful. Others are linked with illness, but nobody yet knows whether the microbes changed first or the illness did.
Clear examples
- C. diff infection: the CDC says most cases happen during or soon after a course of antibiotics, and people are up to 10 times more likely to get it while taking one. Antibiotics can kill helpful gut bacteria along with harmful ones, which lets C. diff grow.
- Small intestinal bacterial overgrowth (SIBO): Mayo Clinic describes it as an abnormal increase in bacteria in the small intestine, often of types not usually found there. Symptoms include bloating, belly pain, diarrhea and unplanned weight loss.
Links that are less clear
Researchers have tied gut dysbiosis to inflammatory bowel disease, obesity and allergies. A 2016 review from Massachusetts General Hospital noted a strong association with inflammatory bowel disease, but said it is still largely unknown whether dysbiosis is a cause or an effect. The same caution applies to the long lists of conditions you may see online, from fatigue to mood problems.
How antibiotics shift the mix
A small but often cited Stanford study followed the gut bacteria of three adults for 10 months through two short courses of the antibiotic ciprofloxacin. Diversity dropped within 3 to 4 days of starting the drug. The bacteria began to return about a week after each course ended, but the community often did not go fully back to where it started. Three people is a tiny sample, so treat this as a picture of what can happen, not a rule. Never stop a prescribed antibiotic early without talking to your prescriber.
Signs people link to dysbiosis
Cleveland Clinic lists bloating, gas and changes in your stool as possible signs of gut dysbiosis, along with signs of infection or overgrowth elsewhere, such as bleeding gums, skin rashes, or painful urination. It also says it is hard to tell when symptoms outside the gut are related to the gut microbiome.
That is the main problem with symptom checklists. Bloating and loose stools are common and have many causes, from a large meal to lactose intolerance to infection. Our guide to signs of an unhealthy gut walks through the most common ones and what else might explain them.
Can you test for dysbiosis?
Doctors can test for specific problems, such as an infection in a stool sample. Cleveland Clinic notes that a breath test can sometimes show which bacteria dominate, which is how SIBO is often checked.
Home microbiome kits are a different matter. An international expert consensus published in 2025 in The Lancet Gastroenterology & Hepatology said evidence for the clinical usefulness of microbiome testing is scarce, and that direct-to-consumer kits are sold without agreed rules or proven value in practice. A kit can describe which microbes were in one sample. It cannot diagnose dysbiosis or tell you what to eat. See our stool test guide for more.
How to support a balanced gut microbiome
Cleveland Clinic says treatment depends on the cause. An infection or overgrowth may need a targeted medicine from a doctor. For everyday habits, it notes that most microbiomes can recover with the right conditions and long-term changes. The steps below are reasonable for most healthy adults.
| Step | What the evidence says | Source |
|---|---|---|
| Eat a wide range of plants | Different gut bacteria use different plant fibers, so variety helps support a healthy balance | Cleveland Clinic |
| Add fermented foods | In a 17-week Stanford trial (18 adults per group), a high fermented-food diet raised microbiome diversity and lowered inflammatory markers | Wastyk 2021 |
| Use antibiotics only when prescribed | Antibiotics can kill helpful gut bacteria and raise C. diff risk; ask your clinician about your risk when starting one | CDC |
| Consider probiotics with care | Effects depend on the strain; one review linked probiotics with antibiotics to about half the risk of antibiotic-associated diarrhea, with moderate-quality evidence | NCCIH |
| Cut back on smoking, alcohol and stress where you can | Listed among factors that can shift the microbiome | Cleveland Clinic |
Fermented foods and fiber
The Stanford trial is one of the better pieces of evidence that food can shift the gut microbiome in people. Volunteers worked up to about six servings a day of foods such as yogurt, kefir, kimchi and kombucha. The fiber group did not see the same rise in diversity during the study. The trial was small and done in healthy adults, so it does not show that fermented foods fix any disease. Our guide to fermented foods for gut health covers practical options, and homemade yogurt is an easy, low-cost way to eat more of them.
Probiotic safety
NCCIH stresses that one strain’s results do not carry over to another. It also says the risk of harm is greater in people with severe illness or weakened immune systems, and that the FDA has warned about severe infections in premature infants given probiotics. Many probiotics are sold as dietary supplements, which do not need FDA approval before sale. If you are recovering from a course of antibiotics, our guide on restoring gut health after antibiotics goes into more detail, and prebiotics vs probiotics explains the difference between the two.
When to see a doctor
Gut symptoms that come and go after a heavy meal are common. Some signs need a proper medical check. Mayo Clinic advises seeing a doctor, especially if you have had abdominal surgery, for:
- Diarrhea that does not go away
- Fast weight loss you are not trying for
- Belly pain that lasts more than a few days
Mayo Clinic says to get immediate care for severe belly pain. The NIDDK also advises talking with a doctor right away for black, tarry or bloody stools, frequent vomiting, signs of dehydration, a high fever, or diarrhea lasting more than 2 days in an adult. People who are pregnant, over 65, taking antibiotics or have a weakened immune system should keep in touch with their doctor when they have diarrhea.
Related topics
- Gut Health: The Complete Guide: the bigger picture on how your gut works.
- Does SIBO Cause Bad Breath?: more on one well-defined type of bacterial imbalance.
- Best Foods for Gut Health: everyday foods that feed a varied microbiome.
- Stool Test for Gut Health: what home kits can and cannot tell you.
- How to Restore Gut Health After Antibiotics: practical steps after a course of treatment.
Sources
- Dysbiosis: What It Is, Symptoms, Causes, Treatment and Diet (Cleveland Clinic)
- Hooks KB, O’Malley MA. Dysbiosis and Its Discontents (mBio, 2017)
- Brüssow H. Problems with the concept of gut microbiota dysbiosis (Microbial Biotechnology, 2020)
- DeGruttola AK, et al. Current Understanding of Dysbiosis in Disease in Human and Animal Models (Inflammatory Bowel Diseases, 2016)
- Dethlefsen L, Relman DA. Incomplete recovery and individualized responses of the human distal gut microbiota to repeated antibiotic perturbation (PNAS, 2011)
- Wastyk HC, et al. Gut-microbiota-targeted diets modulate human immune status (Cell, 2021)
- Porcari S, et al. International consensus statement on microbiome testing in clinical practice (Lancet Gastroenterology & Hepatology, 2025)
- About C. diff (Centers for Disease Control and Prevention)
- Small intestinal bacterial overgrowth (SIBO): Symptoms and causes (Mayo Clinic)
- Probiotics: Usefulness and Safety (National Center for Complementary and Integrative Health)
- Symptoms and Causes of Diarrhea (National Institute of Diabetes and Digestive and Kidney Diseases)
This article is for general information and is not medical advice. Talk to your doctor or a registered dietitian before changing your diet, supplements or medication, especially if you have a health condition.
