Signs of an unhealthy gut: common signs and when to see a doctor

The answer

There is no single sign or test for an unhealthy gut. The signs health sources list most are digestive: gas, bloating, constipation or diarrhea, heartburn and belly pain. Most people have them now and then; healthdirect says that if they happen more often or get worse, they may be a sign of a gut condition.¹ Cleveland Clinic says constipation or diarrhea lasting longer than two weeks needs a provider.⁵

In short

No single test defines an unhealthy gut, and a 2024 review in the journal Gut calls a universally accepted definition of gut health very difficult to pinpoint.⁷Van Hul et al., 2024
The signs health sources list most often are gas, bloating, constipation, diarrhea, heartburn and belly pain.^1,6,3healthdirect; Houston Methodist; Cleveland Clinic
These symptoms can come and go, and healthdirect says that when they happen more often or get worse, they may be a sign of a gut condition.¹healthdirect
Clinicians generally do not use or recommend the gut microbiome test kits sold to consumers, Cleveland Clinic says.³Cleveland Clinic
Constipation or diarrhea that lasts longer than two weeks is a reason to see a provider.⁵Cleveland Clinic

Is there a test for an unhealthy gut?

No. There is no single test, and no agreed definition to test against. A 2024 review in the journal Gut says a universally accepted definition of gut health is very difficult to pinpoint, and Cleveland Clinic says clinicians generally do not use or recommend the gut microbiome test kits sold to consumers. What doctors test for are specific conditions, with blood, stool or breath tests.^7,3

"it is very difficult to pinpoint a universally accepted definition of 'gut health' due to the complexities of measuring gut functionality besides the microbiota composition."
Van Hul and colleagues, Gut, 2024

The same review also says the label often put on an "unbalanced" gut links microbial imbalances to chronic illnesses "without precision or definition." Its authors have ties worth knowing: three of the six edit the journal, and two hold patent applications on gut bacteria and have started microbiome companies.⁷

On home kits, Cleveland Clinic gives the reason plainly: "we still don't know enough about the different types of gut microbiota or how they affect our health to make a report like this useful." Australia's Better Health Channel says there is no clear definition of gut health at all, and Houston Methodist, in an article with gastroenterologist Rachel Schiesser, MD, suggests a simpler route than a kit: "do a simple gut check instead."^3,2,6

What are the signs of an unhealthy gut?

Mostly digestive ones. healthdirect lists bloating, burping or farting more than usual, heartburn, tummy pain, nausea and vomiting, and constipation or diarrhea. Houston Methodist's list is bloating and excessive gas, constipation, diarrhea, heartburn and abdominal pain, and Cleveland Clinic adds poor digestion. The table pairs each sign with what a source says it can reflect and what that source suggests trying.^1,6,3

Signs people mention, what a source says each can reflect, and what the source suggests trying
Sign people mention	What a source says it can reflect	What to try, per the source	Source
More gas or bloating than usual	Gas during or after meals is normal, NIDDK says. More of it can come from swallowed air or foods the gut ferments, or from a digestive condition, which a doctor can check	Less swallowed air, and fewer of the foods and drinks that bring it on; see the 30-day habits	NIDDK ⁸
Constipation	Going less than three times a week, or passing hard, dry or lumpy stools. The most common cause is lifestyle, such as too little high-fiber food, water or exercise; it can also be a digestive condition, which a doctor can check	Fluids, high-fiber foods, exercise, and not holding it in	NIDDK; Cleveland Clinic ^9,5
Diarrhea	Loose, watery stools three or more times daily, or more often than usual for you. Medicines are a common cause; so are stomach bugs, or a digestive condition, which a doctor can check	Adults: talk with a doctor right away if it lasts more than 2 days	NIDDK; Cleveland Clinic ^10,5
Heartburn or indigestion	Often set off by eating too fast or too much, spicy or greasy food, alcohol, a lot of caffeine, smoking or stress; it can also be a digestive condition, which a doctor can check	Allow enough time for meals and chew food completely	MedlinePlus ¹¹
Belly pain or cramps	Cramping usually comes from gas and bloating and is seldom serious; it needs a closer look if it returns often, lasts beyond a day, or arrives with a fever or bleeding from the rectum	Small, frequent meals, plenty of water, regular exercise	MedlinePlus ¹²
A change in stool color	A short change from brown is likely diet-related; deep red, black and tarry, clay-colored or pale stools that do not clear up are a reason to see a provider	Know what is normal for you, and note changes	Cleveland Clinic ⁵
Tiredness, poor sleep or low mood	Listed by one source as possible signs; another says it is hard to tell when symptoms outside the gut relate to the gut microbiome	Enough sleep and stress care; see a doctor for the symptom itself	Better Health Channel; Cleveland Clinic ^2,4

Sources 2, 4, 5 and 8 to 12, linked below. A sign points to a question for you and your doctor, not to a diagnosis. Grams of fiber in everyday foods are in high-fiber foods for gut health.

Which signs are common, and which need a doctor?

Occasional gas, bloating, a day or two of loose or hard stools and the odd bout of heartburn are common, and most settle on their own or with small changes. Signs that last, keep getting worse, or come with blood, black stools, constant pain or a fever are different, and the sources send those to a doctor, not to a supplement or a home test.^1,5,10

Usually common

Some gas, especially during or after meals.
NIDDK
Constipation or diarrhea that clears up within a few days.
Cleveland Clinic
A short change in stool color after a food.
Cleveland Clinic
Gut symptoms that come and go from time to time.
healthdirect

See a doctor

Constipation or diarrhea that lasts longer than two weeks.
Cleveland Clinic
In adults, diarrhea lasting more than 2 days, six or more loose stools a day, or a high fever, right away.
NIDDK
Blood in your stool, or stools that are black and tarry, deep red or maroon.
Cleveland Clinic; NIDDK
Constipation with constant belly pain, vomiting, a fever, or being unable to pass gas, right away.
NIDDK
Indigestion that lasts longer than a few days, or trouble swallowing.
MedlinePlus
Gut symptoms that happen more often or keep getting worse.
healthdirect

What can you do for your gut day to day?

Start with food, movement and sleep, not a product. Houston Methodist lists eating plenty of fiber-rich foods, adding fermented foods, limiting processed foods and alcohol, and exercising regularly, and the Better Health Channel adds chewing well, eating slowly and getting enough sleep. The day-by-day version, with a source for each habit, is our 30-day gut habits checklist.^6,2

Two numbers frame the food side. Houston Methodist says ultra-processed foods make up about 60% of the average American's diet, while Dr. Schiesser adds that "We don't fully understand how processed foods affect the gut microbiome." The Better Health Channel, an Australian state health service, suggests aiming for at least 30 different types of plant-based foods a week.^6,2

Fiber is the habit every source names. Which foods carry the most, per serving, is laid out in high-fiber foods for gut health, and how fermented foods compare with supplements is in fermented foods vs probiotic supplements. Which yogurts still carry live cultures is in is yogurt a probiotic?

Will a probiotic or a gut test help?

Not as a first step, by the sources we read. Dr. Schiesser puts food first, and Cleveland Clinic says clinicians generally do not use or recommend consumer gut microbiome tests. For someone struggling with symptoms who wants to try a probiotic, she suggests a single bottle and a clear stopping point.^6,3

"If at the end of that bottle you don't notice a difference in your symptoms, don't get a second bottle."
Rachel Schiesser, MD, gastroenterologist, Houston Methodist, 2025

What the research on probiotics does and does not show is set out in our research note do probiotics work?

Can tiredness, skin or mood be signs of an unhealthy gut?

The sources are cautious. The Better Health Channel lists "sleep disturbances or fatigue" and stress, low mood or anxiety among possible signs of poor gut health, but Cleveland Clinic says "it's hard to tell when symptoms outside of your gut relate to your gut microbiome." This page goes no further than that: tiredness, skin changes or low mood each deserve a doctor's look on their own terms.^2,4

Where Physician's Choice fits

Physician's Choice, a maker of gut health supplements, publishes this site. This read names no product and argues for none: none of the signs above is a reason to buy one, and the ones that last belong with a doctor.

The short of it

No single sign or test marks an unhealthy gut. Gas, bloating, constipation, diarrhea, heartburn and belly pain are the signs sources list, and they are common now and then; when they last, get worse, or come with blood, black stools, constant pain or fever, see a doctor.

Notes on this page

Where the question came from: Of 1,145 public Reddit posts we read (250 communities, Sep 12 to Oct 12, 2026), 8 used words like gut health or an unhealthy gut. One said "Not sure where to even start on my gut journey!!" (r/GutHealth, Oct 2026), a question, not a review.
What engines were asked: Signs of an unhealthy gut, and how do I know if my gut is unhealthy.
What was left out: Condition names. Where a source ties a sign to a specific condition, this page says "a digestive condition, which a doctor can check".
Sources: 12 sources, each opened on Oct 15, 2026.
Products: None. This site names no product.
Checks: Checked Oct 15, 2026. On Oct 16, 2026 a link to our read on whether yogurt is a probiotic was added. Last checked Oct 28, 2026, when the probiotics section was trimmed. Each later check is dated here.

Questions people ask

How do I know if my gut is unhealthy?

There is no single test. The signs sources list are digestive: gas, bloating, constipation, diarrhea, heartburn and belly pain. Occasional symptoms are common; healthdirect says that symptoms which happen more often or get worse may be a sign of a gut condition, and a doctor can check for specific causes with blood, stool or breath tests.

What are the first signs of an unhealthy gut?

No source we read names a first sign. The ones listed most often are more gas or bloating than usual, constipation or diarrhea, heartburn and belly pain, per healthdirect, Houston Methodist and Cleveland Clinic. A change from what is normal for you, and one that lasts, tells you more than any single symptom.

Can a gut microbiome test tell me if my gut is healthy?

Not reliably, by the sources here. Cleveland Clinic says clinicians generally do not use or recommend consumer gut microbiome tests, because we do not yet know enough about gut microbes to make the reports useful, and a 2024 review in Gut says there is no universally accepted definition of gut health.

When should I see a doctor about gut symptoms?

When symptoms last, get worse, or come with warning signs. Cleveland Clinic says constipation or diarrhea lasting longer than two weeks needs a provider, and adults should call a doctor right away for diarrhea that goes past 2 days, a high fever, or black, tarry or bloody stools, per NIDDK.

Sources

healthdirect (Australian government health service). Gut health. Last reviewed December 2025. healthdirect.gov.au. Opened Oct 15, 2026 through a text reader (the page builds its text with scripts).
Better Health Channel, Department of Health, State Government of Victoria. Gut health. Reviewed 22 January 2026. betterhealth.vic.gov.au. Opened Oct 15, 2026.
Cleveland Clinic. Gut microbiome. Last updated 08/18/2023. my.clevelandclinic.org. Opened Oct 15, 2026.
Cleveland Clinic. Dysbiosis. Last updated 04/16/2024. my.clevelandclinic.org. Opened Oct 15, 2026.
Cleveland Clinic. Changes in bowel habits. Last updated 09/21/2023. my.clevelandclinic.org. Opened Oct 15, 2026.
Houston Methodist. Gut health: signs of an unhealthy gut and how to improve it, with gastroenterologist Rachel Schiesser, MD. April 8, 2025. houstonmethodist.org. Opened Oct 15, 2026.
Van Hul M, Cani PD, Petitfils C, et al. What defines a healthy gut microbiome? Gut. 2024;73(11):1893-1908. PubMed 39322314. Abstract read Oct 15, 2026.
NIDDK. Symptoms and causes of gas in the digestive tract. Last reviewed June 2021. niddk.nih.gov. Opened Oct 15, 2026.
NIDDK. Symptoms and causes of constipation. Last reviewed May 2018. niddk.nih.gov. Opened Oct 15, 2026.
NIDDK. Symptoms and causes of diarrhea. Last reviewed September 2024. niddk.nih.gov. Opened Oct 15, 2026.
MedlinePlus Medical Encyclopedia. Indigestion. Review date 1/30/2025. medlineplus.gov. Opened Oct 15, 2026.
MedlinePlus Medical Encyclopedia. Abdominal pain. Review date 1/13/2026. medlineplus.gov. Opened Oct 15, 2026.

Signs of an unhealthy gut: what is common, and what needs a doctor