Small Intestinal Bacterial Overgrowth (SIBO): Symptoms, Treatment

What Is Small Intestinal Bacterial Overgrowth (SIBO)?

Various bacteria are present in the human small intestine as part of normal intestinal flora, but when they overgrow, they may cause diarrhea. They may also break down bile acids, necessary for absorption of fats, thus reducing absorption of fats and fat-soluble vitamins A, D and E. In severe cases, bacteria may damage small intestinal wall thus impairing carbohydrate and protein absorption resulting in malnutrition. Anemia may develop, when bacteria break down vitamin B12.

Symptoms of SIBO

Symptoms of small intestinal bacterial overgrowth may include:

  • Early satiety (feeling full after only “few bites”), bloating and nausea, which forces many patients to avoid food, resulting in weight loss.
  • Sulphur burps
  • Some patients with SIBO crave sugar.
  • Chronic diarrhea – may appear weeks or even years after the causing event, like surgery (1).
  • Whitish, floating, foamy and sticky stool due to unabsorbed fats.
  • Muscle weakness and bone pains due to vitamin D deficiency.
  • Anemia with pale skin, weakness or tingling due to vitamin B12 deficiency.
  • Impaired night vision due to vitamin A deficiency.

Causes of SIBO

Why bacteria in the small intestine overgrow?

  • Ileocecal valve, separating the small and large intestine, may be insufficient due to inborn errorsbowel surgeryCrohn’s disease or other disorders, thus enabling bacteria from the large intestine, where they are present in large amount, to invade into the small intestine.
  • Slow intestinal motility, due to low gastric acid, acid-lowering drugs, like Prevacid, or pain-killers , like opiates, nerve damage in diabetes or overgrown fibrous tissue in systemic sclerosis, may allow bacteria to stay in the small intestine for a long time without being flushed away.
  • Liver disease, like cirrhosis.
  • Irritable bowel syndrome (IBS). Relation between SIBO and IBS is not entirely understood.

Diagnosis of SIBO

SIBO is diagnosed by a hydrogen breath test. A patient drinks a solution with sugar, which is broken down by small intestinal bacteria that yield hydrogen. Hydrogen enters the blood and appears in exhaled air, which is collected by a special machine. From an amount of hydrogen in the exhaled air, an amount of intestinal bacteria can be calculated.

Treatment of SIBO

SIBO is treated with antibiotics. Probiotic capsules given along with antibiotics help to maintain normal intestinal flora (1). Vitamins, minerals and other nutrients may need to be replaced; in severe malnutrition, intravenous feeding may be required


A person with poorly controlled diabetes, chronic gastrointestinal disease or recent surgery, experiencing excessive bloating, early satiety or sulphur burps, should consider small intestinal bacterial overgrowth as a possible cause.

Related Articles:


  1. Small intestinal bacterial overgrowth  (
About Jan Modric (249 Articles)
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  • VeganGroomer

    Hello Jan,
    Please advise:
    I am quite sure that I have SIBO, I have an appt on Monday with a new GI. I have not had a breath test yet.
    1)What to ask my new GI about SIBO? So many GI’s and GP’s are not familiar with SIBO. I am also looking for a nutritionist or ND to help with a diet plan for me since I am a vegan. Hope to hear back from someone today.
    2) I live in Los Angeles, would you recommend that I try to get a secondary appt with Dr. Pimentel @Cedars-Sinai(leading researcher) or is it not necessary. Since I don’t have health ins, it may be moot anyhow.
    3) I ordered Dr Pimentel’s book, do you recommend following his instructions?
    I have been on an elimination diet for about a month, and I still have all the symptoms of SIBO and possibly FM too.
    Bit of an uphill battle…

    • Jan Modric


      you can write down:

      – your main (one) current symptom, and other current symptoms
      – complete personal and family medical history, including diseases, diagnoses, treatments and diet..all put in a time line. Which foods, if any, aggravate or relieve symptoms? This questionnaire may help:

      Doctors hate when you come up with some diagnosis first. Common causes of bloating (?) and indigestion (?):
      – large amount of soluble dietary fiber
      – fructose malabsorption
      – lactose intolerance
      – IBS (irritation of bowel by certain foods or stress)
      – intestinal parasites
      – celiac disease…

      SIBO may be a cause or result of fructose malabsorption. I believe that a single breath test can difffer these two.

  • Mykul Oh

    Hi! My name is Myk.I have no health Insurance.I have had a problem of diarrhea for about a year or more. I had a problem with my pancreas 3 years ago. I have been taking 2 or 3 vitamins Chromium picolinate(1000-1500mg, aday) magnesium (2000mg),and a multi vitamin. My pancreas seems to be better,but my stool has not,but last month I changed brands. I used Finest Natural for Chrom, and mag. I started using SUNDOWN NATURAL Chrom. All of a sudden my diarrhea went away and my stool was hard. Well 4 weeks went by and everything went OK. Then, The diarrhea started back up. My diet remain the same,but I’m confused.I eat a lot of veggies and fruits, not much sugar,lots of water,After reading the article a lot of the symptoms were some that I have experienced. Does any body have some good advice on what to do.I’m unemployed so I cant afford a doctor.I figure there should be away to naturally cure this problem I pray! Ty

    • Jan Modric

      Mykul Oh,

      in case you have developed a fructose malabsorption, a low-fructose diet, and in lactose intolerance, a lactose-free diet would help in few days.

      SIBO may be sometimes accompanied by above two disorders and can go away with the diet. Sometimes treatment with antibiotics is needed (after making a diagnosis).

      I have no idea were the supplement you take prescribed or you started them on your own. Magnesium may act as a laxative.

  • Irina

    Hi Jan,

    My boyfriend was diagnosed with SIBO and was prescribed Xifaxin, which did not help him. We are doing research on diet to see if this will help him feel better. I keep seeing that grains are to be avoided… would eating gluten-free foods take care of this (or are these unrelated?) Also, it seems like the only thing he can eat for breakfast are eggs (any other ideas?), but he fries these to make scrambled eggs/omelet with turkey bacon… is frying hard on the stomach? Which fruits (if any) can be eaten? Which veggies should be avoided? Any other tips are greatly appreciated… we are trying very hard. Thanks in advance, Jan!

    • Jan Modric


      SIBO often has some discoverable cause. If he has:

      – celiac disease, he should avoid wheat, barley and rye and any commercial product containing gluten (gluten-free diet). In celiac disease, he would still likely tolerate corn and buckwheat.
      – lactose intolerance, he should avoid milk products and any commercial product containing lactose (lactose-free diet).
      – fructose malabsorption, he can try this low-fructose diet

      If I assume he has all above disorders (not likely), he would still likely tolerate fresh meat and fish (unbreaded), oils, eggs, corn, buckwheat, lettuce, spinach (without cream). Also, if I assume the antibiotic has killed enough bacteria, and he has no SIBO now, it may be an ideal time to have at least a 4 day diet trial containing only abovementioned foods. In this time symptoms should lessen obviously. When he is symptoms free, he can add one food from each group at a time, for example an apple and wait two days – if he can tolerate it, he does not likely have fructose malabsorption, and he can likely eat other fruits. Then he can try some milk, and wait two days – if he can tolerate it, he does not likely has lactose intolerance, and he can likely tolerate other milk products. Then he can try wheat. If he can tolerate it, he does not likely has celiac disease. Official tests for all mentioned disorders exist. If nothing helps, he might need additional test, like stool test for parasites.

  • nh

    Hi Jan,

    I have been suffering with chronic diarrhea for seven months now. I’ve had blood tests, stool tests and a flexible sigmoidoscopy in that time. I avoid dairy and wheat products as this mildly relieves symptoms. The only time I get significant relief is when I take antibiotics, which my doc has prescribed on the 3 occasions; the most effective was cipro…I was back to normal, but when I finished the course the symptoms returned (very frequent, irregular bowel movements, fatigue…often after I eat I would have to live near the toilet for a couple of hours). When I was taking cipro, I pretty much could anything without any adverse effects. I saw a specialist who believes I have SIBO and thinks that a 3 month, less intense course of cipro with probiotics is the next step. I’m a bit concerned since it seems as though I might not be treating the real cause, and my symptoms will return. Is there a possibility of an intestinal parasite in this case; I usually have a blood/stool test after finishing my course of antibiotics so I’m worried that something might not be showing up because of that (sorry my doc’s orders not mine).

    Thank you so much!

    • Jan Modric


      – SIBO is diagnosed by a breath test
      – Intestinal parasites are diagnosed with a stool test
      – Clostridium difficile (bacterium) overgrowth in the colon (with a typical barnyard smell of gas) is diagnosed with a a stool test for Cl-diff toxin.
      – Infections by bacteria, like shigella or salmonella do not usually last for 7 months

      Cipro could possibly be at least partly effective in all above conditions.

      Besides infection or bacterial overgrowth, some food intolerance could be possible:
      – celiac disease
      – fructose malabsorption
      – lactose intolerance

      so you might want to have a few-days lasting diet trials for each condition. Here’s a list of foods to avoid in fructose malabsorption.

  • ashleyann00

    Hi Jan.I have been sick for 6 months with watery to soft diarehea,nausea,weakness,weight loss,dizziness,malabsorbtion etc.In 4 months i lost 18 lbs.I have had 22 stool tests for parasites-even one from diagnostech lab-all negative.My liver/pancreas function are fine and complete blood count-fine.I did test positive for sibo.Im on day 8 of 14 and not noticing to much difference.My stools are still mush with undigested food.I tested neg for celiac,lactose intolerance.I also in a stool test found out i had +2 candida albicans…not sure how accurate this is?Please give me some advice.
    ps also have a small gallstone.

    • Jan Modric


      candida is, to some extent, normally present in the bowel, so being positive for candida by itself is not necessary considered as an infection at all. I don’t really know what “+2” could mean. A massive candida infection of the bowel can occur in lowered immunity – in this case you would be probably terribly ill, though. I also do not know who exactly has performed all these tests, but I believe an infectologist could reliably explain your candida test result.

      SIBO is often accompanied with certain food intolerances, like fructose malabsorption (FM), meaning that treating SIBO, but not FM (or vice versa) would not result in symptoms relief. I recommend you to complete the full course of antibiotics as prescribed, and consider to have a low-fructose diet.

      Gallstones cause diarrhea only when a gallbladder full of stones presses upon the bile duct, or a small bile stone sticks within the bile duct and blocks the bile flow. In this case stools are greyish (no color) with white patches, foamy, frothy, sticky and floating. You’ve said your liver function is fine – in this case, gallstones are less likely to be a cause.

      Dizziness could be partly due to dehydration, so try to drink enough water and get enough calories. If any mineral/vitamin deficiences were discovered, I guess you got some supplements prescribed.

  • ashleyann00

    Jan thank you so much for your response.I do believe i have fructose intolerance and probably a very dammaged intestinal wall since i have had this for about 6 months.Anything you reccomend to heal the gut?Its crazy to say but gee i wish i could see just one normal bowel movement…and i would feel like im getting somewhere.Also I have alot of pressure under my ribcage,feels as if i have a baby in there with feet in my ribs!I have been through 2 pregnancies so thats the best i can describe the feeling lol.Maybe gas/bloating?I feel my immune system is ok-I had a cold a few weeks ago and got over it faster then my perfectly healthy husband.I wantto mention too that I took flagyl a couple months ago-only 4 days and did get thrush.Also right now i have a yellow/white coating on my tongue..doesnt look like my thrush did the last time.

    • Jan Modric


      if you have fructose malabsorption, 3-4 days of a low-fructose diet should result in an obvious symptoms relief. There’s no other treatment for fructose malabsorption. I can’t exclude other intestinal disorders. In fructose malabsorption and SIBO, the intestine may be inflamed, but it should heal on its own with resolution of FM or SIBO.

      Flagyl is a strong antibiotic and it may kill both good and bad bacteria in the bowel, allowing yeasts (thrush – white tongue) to overgrow. White tounge can also result from various other gastrointestinal disorders. Maybe a low-fructose diet can help.

  • Rachel

    On and off for the past 15 or so years I have had episodes of sulphur burps, sometimes combined with constipation/diahhroea. I have been to the doctor a few times about it but it has always cleared up by itself – usually i stop eating for a few days. However, lately, over the past couple of months it has recurred much more frequently. I do crave carbs/sugar although I am diabetic type II. Is it likely to be SIBO? Thanks for your help.

    • Jan Modric


      sulfur burps are caused by hydrogen sulfide which is produced by either normal or pathogenic intestinal bacteria or parasites when they get enough food (usually sugars). SIBO is one possible cause, diagnosis is with a breath test. Other causes include: intestinal parasites, like giardia, Helicobacter pylori, food intolerances (fructose malabsorption, lactose intolerance, celiac disease), Crohn’s disease.

      Few days lasting diet trials (a low-fructose, lactose free or gluten free) usually result in symptoms relief when one of the food intolerances is the cause. Regarding you are diabetic you should speak with your doctor about these trials, though. Here in the sulfur burps article is some additional explanation.

  • ashleyann00

    Can you tell me what other disorders can cause a coated tongue?Day 10 of xifaxan seems to be helping a bit.What is your opinion on liver/gallbladder flushes?Are they safe?

    • Jan Modric


      – thick, greasy, whitish/yellowish and easily removable patches would speak for a yeast infection (thrush)
      – gastric acid reflux would be likely associated with a heartburn and whitish foamy saliva, or only whitish tongue, but reflux alone would not likely cause diarrhea
      – so, you can first think about SIBO and possibly associated fructose malabsorption.

      I do not recommend you any liver or gallbladder flushes (except from what a registered gastroenterologist might prescribe you), since these do not likely treat gallstones or liver diseases.

  • ashleyann00

    jan,can you tell me what other disorders may involve white tongue?I just switched gi docs bc i wasnt getting much help after 4 months.I hope he can find something that the other couldnt.

  • vanessa

    Hi I had H pylori 4 years ago, now had a re- occurance of same symptoms but tested negative. I have soreness in stomach, wind and gurgly upper left (stomach)frequent belching…Any ideas what could be causing this? i eat well fruits veg no wheat, non smoker, into sports….Many thanks

    • Jan Modric


      theoretically, a test for H. pylori could be false negative. SIBO, fructose malabsorption, gastroparesis are some of other possible causes.

  • Cindy

    Hi Jan,
    Thank you for this great article!
    For the past 9 months I’ve been suffering with symptoms including nausea, bloating constipation and weight loss brought on after a severe case of food poisoning.
    I’ve noticed that these symptoms are triggered by foods such as honey, chickpeas, onions, soy and other starchy foods. I’m currently on the low FODMAP diet and it helps quite a bit. I’ve deducted that I have some form of carbohydrate malabsorption. My questions are:
    1) Which sugar solution should I be drinking (lactose, fructose, lactulose or sorbitol)for the Hydrogen Breath Test if I was to test for SIBO? I’ve already done the test once drinking glucose and the results were negative.
    2) What correlation is there between the trigger foods I’ve listed?
    3) If I don’t SIBO, what else can it be? I have tested negative for both Celiac & H.Pylori

    Thank you for reading my question.

  • Andrew


    I have exactly the same symptoms as Cindy. I also will get fatigue and loss of appetite during a flare up. Do you know what it could be?


    • Dr. Chris

      Hi Andres

      Please note that every case is now answered on its own. State your symptoms and experience and we may be able to guide you.

      Often we get readers who say “my symptoms are the same as …” and then once answered, there post several comments/questions afterwards (practically spamming us) saying that some point is different and so on. It wastes a lot of our time. Sorry for having to be firm on this but it is the editor’s rule.

  • Andrew

    Thanks for the clarification. It started out as diarrhea. Then it stopped and for a few months now I have suffered from weight loss, dull stomach cramp, sometimes bloating, pale skin, constipated hard stools or stools that look rough/undigested. During flare-ups, my symptoms are nausea, brain fog, fatigue, anxiety, and lack of appetite. These flare ups can last a week and I believe it’s probably triggered from food like soy or fried food.

    No matter how much I eat now, I can’t seem to gain any weight.

    I have done blood tests (including celiac), stool tests, urine tests, xray, ultrasound, and h pylori breath test…and they have all come back negative so far.

    What are the possibilities of what I have?

    Thank you

    • Dr. Chris

      Hi Andrew

      Even though many of these tests came back negative, your symptoms are a cause for concern and any doctor would have advised further investigative options. If you have not followed through with these additional tests, then please do so.

      Your symptoms may be indicative of conditions resulting in pancreatic exocrine insufficiency (read more pancreatic enzyme deficiency), biliary and liver diseases. This could be caused by pancreatitis, gall stones or gallbladder diseases, hepatitis, and even cancer of these organs or the gut itself. While conditions like IBS may also be a consideration, the weight loss (if unintentional) needs to be looked into and the more serious causes excluded. If you have not alread done so, you need to consult with a gastroenterologist. There is no way we can conclusively identify what the cause may be.

  • ashleyann00

    Cindy and Andrew-I have same syptoms!Weight loss is my biggest concern at this point.I am down to 105 and am 23 years old.No matter how much I eat I cant gain a single ounce!I have had colonoscopy/endoscopy.ultrasounds,xray,capsule endo,stool tests etc.I have tested negative for celiac and hpylori.Capsule study showed no damage to my small intestine.I have had 2 breath tests one which was positive several months ago and just had another recently.I dont know if i have fructose malabsorbtion as well?My stools are always different,sometimes soft,sometimes watery and frothy.I just had blood work-LFT,esr,c reactive protein,cbc,comp betabolic,amaylase-all came back normal!However i do have a vit D deficiancy.I would give anything to fix this ongoing problem,its been almost a year now with consistant weight loss and horrid symptoms.

  • Andrew

    ashleyann00 and Cindy:
    is there any way to contact you? Maybe we can figure something out.

    Dr Chris:
    thanks for the response I’ll look into those things. I have a GI booked but it takes time to see them unfortunately.

    • Dr. Chris

      Hi Andrew

      You are welcome. Sorry that I cannot comment further. Our updated editorial guidelines have restricted us in just how much we can say as it can be misleading to some readers. Although this is a free service, some users actually harass us if their doctor disagrees with our advice.

      Ashleyann00, Cindy and Andrew : Please note that we do not allow for an exchange of contact details on this platform. Once your details are public here it may fall into the hands of spammers. Consider social media instead.

  • ashleyann00

    I have seen 3 gastro doctors.Good luck Andrew I hope someone will be able to help you,because I have gotten nowhere!Just got my breath test results this morning-they were inconclusive-so useless basically.I started takign digestive enzymes yesterday,and im going to take them with every meal to see if it helps.I am deficiant in Vitamin D only.Evrythign else is fine-so I am assuming if I had celiac or malabsorbtion then i would be defficiant in alot more.Is that correct?I have tested negative for celiac by biopsy and blood as well.I just can’t seem to make sense of anything!Neither can my doctors…it is very frusterating!!!!I feel as though my symptoms”flare up” as well!And like you,during that time i have no apetite and nausea.Im sorry to ask such personal questions but are your bm’s loose and sometimes watery and frothy/foamy???I am wondering if I have crohns and it was missed during my colonoscopy.Or maybe a gallbladder problem?I dont know,im not a doctor,just a guess.

  • Andrew

    Dr. Chris: Would a GI specialist be the one to consult for pancreatic exocrine insufficiency? I am seeing one soon. What kind of test(s) should be done to find it?

    ashleyann00: what do you think triggers your symptoms to flare up? To answer your question, I had loose explosive stools for the first few weeks. I normally don’t have loose stools anymore. They are usually hard and/or thinner & smaller than usual.

    • Dr. Chris

      Hi Andrew

      Yes, you should see a gastroenterologist. While your GP or other specialist physicians could help as well, this is the gastroenterologist’s specialty. You can read more on Pancreatic Enzyme Tests.

  • what could cause pain in right upper thigh more on the right side of the thigh? It does travel into the sciatia and sometimes affects my walking. I had xrays of my hips and it showed nothing abnormal. Any ideas? Thanks Abby

  • KM

    Hi, I have recurrent SIBO. My question is what are the underlying conditions that causes SIBO recurrent?, especially the nuero and muscular conditions.