Symptoms
SIBO can cause gastrointestinal symptoms, but the symptom pattern is not specific. Many patients with bloating, gas, diarrhea, constipation, or abdominal discomfort have another condition or more than one contributing diagnosis.
Key point
Symptoms can raise suspicion for SIBO, but symptoms alone cannot diagnose it.
Common Symptoms
Patients may report:
- bloating
- visible abdominal distension
- excess gas or belching
- abdominal discomfort or cramping
- diarrhea or loose stools
- constipation
- nausea
- early fullness
- food intolerance
- fatigue
Symptoms Suggesting Malabsorption
More clinically significant SIBO may contribute to malabsorption. Possible features include:
- unintended weight loss
- greasy or difficult-to-flush stools
- anemia
- vitamin B12 deficiency
- iron deficiency
- low fat-soluble vitamins in selected cases
These findings warrant medical evaluation rather than self-treatment.
Why Symptoms Overlap
SIBO symptoms can resemble:
- irritable bowel syndrome
- celiac disease
- inflammatory bowel disease
- lactose intolerance
- fructose intolerance
- pancreatic insufficiency
- bile acid diarrhea
- medication adverse effects
- constipation with overflow diarrhea
- gastroparesis or other motility disorders
When to Seek Medical Care
Seek medical care promptly for blood in the stool, black stools, unexplained weight loss, persistent vomiting, fever, dehydration, anemia, progressive difficulty eating, severe pain, or new gastrointestinal symptoms after age 50.
What to Track Before an Appointment
A symptom diary can help your clinician. Track:
- stool frequency and form
- bloating severity
- foods that worsen symptoms
- weight changes
- antibiotic use
- laxative or antidiarrheal use
- prior surgeries
- current medications and supplements