Probiotics and Prebiotics: Which for Which Condition

Dietary supplement (live microorganisms and fermentable fibres)

Probiotics: Saccharomyces boulardii, Lactobacillus rhamnosus GG, multi-strain products; prebiotics: inulin, fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS). Brand names vary and are given only as product types, not endorsements.

Probiotics are live microbes that, in adequate amounts, may give a health benefit; prebiotics are food components (mostly fermentable fibres) that feed gut bacteria. The key scientific point is that effects are strain-specific and condition-specific: a result for one strain in one disease cannot be assumed for another strain or another disease. The AGA 2020 guideline on probiotics in gastrointestinal disorders, the World Gastroenterology Organisation (WGO) guideline on probiotics and prebiotics, and ESPGHAN (European paediatric gastroenterology society) position papers all rate most of the evidence as low or very low quality and give recommendations for named strains only. This page does not repeat the general explanation in our article on probiotics; it focuses on which condition has what level of evidence.

Because products differ, check the label for the exact strain name (genus, species and strain code), the number of live organisms until the expiry date, and storage instructions; follow the label and your doctor’s or pharmacist’s advice for how much to take. If the condition is one where evidence exists (for example, antibiotic-associated diarrhoea), it is usually started with the antibiotic course. For IBS, set a trial period (about 4 weeks), note your symptoms, and stop if you see no clear benefit; do not keep buying products indefinitely. Take it separately from the antibiotic dose if the label or pharmacist advises. A probiotic is never a replacement for a prescribed treatment. Yoghurt and laban with live cultures are reasonable foods for most healthy people but do not contain the specific strains studied in the trials.

• Fever, chills, low blood pressure or feeling very unwell while taking a probiotic, especially with a weak immune system, a central venous line, or a serious illness — Rarely the live organisms (bacteria or yeast) enter the bloodstream and cause a serious infection. Stop the product and go to the emergency department urgently; tell them you take a probiotic.

• A premature or very sick baby who is feverish, not feeding, has a swollen belly, vomits green fluid or is very drowsy after being given a probiotic — Possible serious infection or bowel injury. Go to the emergency department immediately.

• Swelling of the lips, face or throat, wheeze, or widespread rash — Could be a serious allergic reaction. Call emergency services now.

• Severe or worsening belly pain, bloody diarrhoea, black stools, or diarrhoea that persists after antibiotics — A probiotic does not explain or treat these. They may be C. difficile infection or another serious problem; see your doctor urgently and do not rely on a probiotic.

Who should AVOID probiotics unless their specialist agrees: people with a weakened immune system (for example on high-dose steroids, azathioprine, biologics or chemotherapy, after transplantation, or with advanced HIV), people with a central venous catheter or parenteral nutrition line, people who are critically ill, people with severe acute pancreatitis (a large Dutch trial, PROPATRIA, found more deaths with a multi-species probiotic in predicted severe pancreatitis), people with heart-valve disease or recent bowel surgery with a leak risk, and premature or very sick infants outside the neonatal unit. Antibiotics can kill bacterial probiotics (yeast products such as S. boulardii are not killed by antibiotics, but the yeast is the one linked to bloodstream infection in people with central lines). Pharmacists can advise on spacing from antibiotics. Probiotics sold as supplements are not tested like medicines and contents may differ from the label.

There is no routine blood test. Keep a symptom diary for 2 to 4 weeks (stool frequency, bloating, pain) to judge honestly whether it helps. People with pouchitis or IBD should tell their specialist, who decides on any product and follows disease activity with usual tests.

Stop if there is no benefit after a fair trial, if symptoms worsen, or if any red-flag symptom appears. Stop and tell your doctor before any planned surgery, chemotherapy or transplant, or if a central line is placed.

Probiotic foods are generally fine in pregnancy and breastfeeding. For supplements, there is no strong evidence of harm in healthy women, but ask your doctor or midwife first, especially if you have other conditions.

Laban, yoghurt and other fermented dairy are part of the local diet and are a food-first option; choose pasteurised, unsweetened products from trusted sources. Probiotic capsules and powders are widely sold in pharmacies, supermarkets and online, and some are advertised for conditions without evidence. Ask the pharmacist for the strain name, and check that the product is registered with the SFDA. Take extra care during travel (including Umrah and Hajj) if you rely on a refrigerated product.

• Is there evidence for a specific probiotic strain in my condition, or is it only a general claim?

• Is it safe for me given my immune system, medicines, central line or recent surgery?

• Should I take it with my antibiotic course, and for how long?

• If my bloating is the main problem, would diet changes or another treatment be a better first step than a probiotic?

This guide comes from the Saudi Gastroenterology Association (SGA) patient library, prepared by the Approved for publication by SGA; individual clinician review is ongoing. Last reviewed: 2026-04-24. It is for education and does not replace your doctor's advice.