Feeling constantly bloated, fatigued, or dealing with unpredictable digestion? You’re not alone! Many people struggle with mysterious gut issues, and one sneaky culprit could be Small Intestinal Bacterial Overgrowth (SIBO). Some are mysterious because doctors call them IBS, even though they’re something else…. According to a research review published in March 2017, almost 78% of people with IBS have SIBO, compared with up to 40 percent of people who do not have IBS. So what are some signs that you might have SIBO? I’m sharing 12 signs that count point to SIBO instead of something else.

1. Persistent Bloating

Bloating that seems to appear out of nowhere—or that escalates after every meal—can be a key indicator of SIBO. You might feel as if your waistband is constantly tight, or notice your stomach getting progressively more distended as the day wears on. This bloating isn’t just typical post-meal fullness. It can feel downright uncomfortable, sometimes even painful, and often subsides only when you skip meals or drastically reduce your carb intake.

The bacteria in your small intestine thrive on eating carbs, which is why you may feel more bloated after a pasta dinner or a bowl of cereal than your friends or family do. For those of you who have used the low-FODMAP diet, maybe even successfully to combat this bloating, you know what I’m talking about.

2. Excessive Gas (Burping or Flatulence)

If you’re constantly burping after meals, or if your flatulence feels embarrassing, it might not just be your food choices. With SIBO, bacterial overgrowth leads to the production of gases like hydrogen and methane in the small intestine. These gases have to go somewhere—hence frequent burping, bloating, or passing gas. Why there is more gas with these bacteria? The food they eat and ferment, leads to gases. For some people this leads to bloating, because the gas gets trapped and for others this means the gas finds other ways to get out of the body!

Sometimes, the odor can be particularly strong or “sulfur-like,” which is a further clue that it could be a specific type of SIBO, called hydrogen-sulfide SIBO. While occasional gas is normal, an uptick that coincides with certain types of foods (especially high-fiber or high-carb) can be an important sign to investigate.

3. Chronic Diarrhea or Constipation

SIBO can wreak havoc on your bowel habits in more ways than one. Some individuals find themselves running to the bathroom multiple times a day with loose stools that just won’t let up. Others may swing between diarrhea and constipation, never quite sure which version of digestive distress the day will bring. This unpredictability stems from how bacterial overgrowth affects intestinal motility or: the slowing or speeding up the movement of food through your system.

Food is supposed to go through your digestive tract for 36 hours.(1) So if there’s immediate diarrhea after you’ve eaten, that might also be an indicator of something else. If you’ve tried eliminating certain foods or upping your fiber intake to no avail, SIBO might be playig a bigger role than you think.

 

 

 

4. Unexplained Fatigue

Tiredness that lingers well after a good night’s sleep is another common complaint among people with SIBO. Because bacterial overgrowth disrupts nutrient absorption, your body may be running on less fuel than it needs. Plus, chronic gut inflammation can add to the overall burden on your system. If you find yourself yawning through mid-afternoon meetings or struggling to focus during regular daily tasks, even though you’re getting enough sleep, it could be time to look deeper into what’s going on in your gut.

5. Food Sensitivities

Have you recently become lactose intolerant or started reacting badly to foods like onions, garlic, apples, or wheat products? An uptick in food sensitivities—or noticing that high-FODMAP foods leave you feeling bloated and lethargic—can point to SIBO. When bacteria build up in the small intestine, they ferment certain carbohydrates much sooner in the digestive process than they’re supposed to. The result is not only bloating and gas but also an increased sensitivity to foods you once enjoyed without a second thought.

I have tried so many diets, while under the supervision of dieticians and their ultimate conclusion was: you’re just sensitive to everything.. Even ‘good’ foods were bad for me… Looking back that was a clear indicator something else was going on.

6. Abdominal Pain or Cramping

Discomfort or cramping in the lower abdomen, especially shortly after meals, is a classic sign something is off in your gut. The pain may be sharp and intense or come in waves of dull aches. Sometimes, it subsides if you can manage a bowel movement or if enough time passes without eating. In SIBO, the presence of extra bacteria creates more gas and other byproducts that irritate the intestinal lining, contributing to pain or cramping. If antacids or over-the-counter solutions aren’t helping, it’s worth looking into deeper causes like SIBO.

7. Nutrient Deficiencies

Brittle nails, thinning hair, or trouble maintaining healthy iron and B12 levels could point to malabsorption linked to bacterial overgrowth. While eating a well-rounded diet is typically the first step for adequate nutrient intake, SIBO can mean your body is missing out. The excess bacteria end up consuming or altering nutrients before they can be fully absorbed, leaving you with chronic deficiencies even when you’re trying to eat healthily. Over time, this can lead to fatigue, weakened immunity, and other deficiency-related issues.

8. Unintentional Weight Loss or Gain

Weight that swings in either direction without a clear lifestyle or dietary change might connect back to your gut. Some individuals experience unwanted weight loss because, despite eating enough, they aren’t absorbing nutrients properly. Others deal with stubborn weight gain as inflammation, gas, and fluid retention inflate the number on the scale. If your usual strategies for weight management suddenly stop working—or if your appetite and eating habits haven’t shifted yet your weight does—take note. SIBO could be a hidden factor.

9. Bad Breath (Halitosis)

Most people blame bad breath on poor oral hygiene, but if brushing, flossing, and mouthwash aren’t helping, your small intestine might be the culprit. Certain bacteria produce sulfuric compounds and other odors that can travel back up into the esophagus and mouth. When these populations are overgrown, you might notice a persistent “rotten egg” smell in burps or a general bad breath that’s resistant to mints and mouth rinses. If you’ve tried everything else to tackle halitosis, look further down your digestive tract for answers.

Again, this might especially be a symptom of hydrogen sulfide SIBO.

10. Skin Issues (Acne, Eczema, or Rosacea)

Your skin often reflects your internal health, and an imbalanced gut can show up in more places than just your stomach. Acne breakouts, rashes, or flare-ups of eczema and rosacea may appear or worsen when your gut is under strain. SIBO can trigger systemic inflammation, affecting the skin’s barrier and immune response. If you’ve noticed a direct correlation between digestive upset and new or worsening skin problems, investigating SIBO might be a significant step toward clearer skin and a happier gut.

11. Mood Swings or Anxiety

It may surprise you to learn that your gut and brain communicate constantly through what’s called the gut-brain axis. When bacterial imbalances throw off the production of important neurotransmitters like serotonin, you might feel more anxious, stressed, or even depressed. Digestive discomfort and the stress of dealing with it can further fuel mood swings, creating a cycle that’s hard to break. Recognizing this connection can be the first step toward addressing both mental and physical symptoms more effectively.

I struggled with so many mood and mental health issues, I was afraid it would never get better. Unfortunately, none of the mental health experts (therapists etc.) would look at physical causes and vice versa! But it does get better. Here’s a blog post on more in-depth information on the relationship between mental health and SIBO.

12. Trouble Sleeping

Struggling with insomnia or waking up multiple times during the night is another way SIBO can affect overall well-being. Ongoing digestive discomfort may prevent you from relaxing fully, while chronic low-grade inflammation can mess with hormones like melatonin that regulate your sleep-wake cycle. If you’re tired of tossing and turning and suspect a deeper link to your digestive problems, it’s worth exploring whether bacterial overgrowth is contributing to your sleep issues.

So what can you do if you have these signs of SIBO?

What Causes SIBO?

SIBO doesn’t just happen overnight. Often, there’s a combination of factors at play. Low stomach acid is one known contributor because it fails to kill off bacteria that should never survive into your small intestine. Slow gut motility, where food and waste linger longer than they should, also invites bacterial buildup. A diet high in refined carbs can feed the wrong microbes, encouraging them to flourish. Previous gut infections or food poisoning can alter the delicate balance in your intestines, setting the stage for SIBO later on. Chronic stress further disrupts digestion and can weaken the gut-brain connection, making your system more vulnerable to overgrowth.

 

How to Test for SIBO

Breath tests are the most commonly used method for diagnosing SIBO. After ingesting a sugar solution such as lactulose or glucose, you’ll breathe into a collection device at set intervals. If excess hydrogen or methane shows up, it signals that bacteria are feasting on that sugar in your small intestine. Some practitioners may also recommend stool analysis to check the broader microbiome or blood work to spot nutrient deficiencies that might hint at malabsorption.

Here is a full blog post explaining what to do and how to do a breath test.

Treatment & Lifestyle Changes for SIBO

SIBO treatment often starts with a targeted plan to reduce bacterial overgrowth and stop it from coming back. Your healthcare provider might prescribe antibiotics like rifaximin or recommend herbal antimicrobial supplements, depending on your specific situation. Dietary adjustments are key—many people find relief by following a low-FODMAP or Specific Carbohydrate Diet (SCD), which reduces the fermentable carbs bacteria love. Prokinetics can help ensure your gut motility improves, preventing food from lingering and feeding excess bacteria. Stress management techniques—anything from mindful meditation to gentle yoga—are also essential because chronic stress can undermine even the best gut-healing strategies. In some cases, reintroducing the right strains of probiotics or using digestive enzymes can help rebuild a healthier microbiome and restore proper nutrient absorption.

 

Conclusion

If you recognize multiple symptoms from this expanded list of signs you have SIBO—persistent bloating, unexplained fatigue, frequent food sensitivities, or even pesky skin issues—it’s worth considering that SIBO might be influencing your day-to-day health far more than you realize. The upside? With proper testing, tailored treatments, and consistent lifestyle adjustments, you can regain balance in your gut and experience a noticeable improvement in your overall well-being.

Still not sure where to begin? Scheduling a consultation with a functional medicine practitioner or a gastroenterologist is a wise first step. They can help you arrange the appropriate breath tests and craft a personalized plan that addresses your symptoms at their root. Your gut plays a huge role in everything from digestion to mood regulation, so giving it the attention it deserves can yield benefits that ripple through every part of your life. Don’t let SIBO remain an unseen (and uncomfortable) guest in your body—take steps to kick it out and reclaim your vitality. If your doctor doesn’t listen, please try and find another one that does. Unfortunately for us, SIBO is not yet famous enough, so a lot of doctors will dismiss it.