Probiotics After Antibiotics: Which to Choose and How to Take Them

At the pharmacy, this is one of the most common questions: “I’ve been prescribed an antibiotic, what else should I buy for my gut?” Often the person is already holding a box that just says “lacto- and bifidobacteria” with no strain listed.

Below: when a probiotic is needed, which strains have evidence and how to combine them with an antibiotic so you don’t waste money.

Why antibiotics cause diarrhea

An antibiotic can’t tell “bad” bacteria from “good” ones. Along with the infection, part of the normal gut flora dies. Carbohydrates are digested less well, bile acid metabolism changes, and stools become loose.

This is called antibiotic-associated diarrhea. Depending on the study, it affects 5-35% of people taking antibiotics. It is more common with broad-spectrum drugs: amoxicillin with clavulanic acid, cephalosporins, clindamycin and fluoroquinolones.

The most dangerous form is caused by the bacterium Clostridioides difficile. It multiplies when there are fewer competitors in the gut and can cause severe colitis. The risk is higher in people over 65, in hospital and after several courses of antibiotics.

After a short course, gut flora usually recovers on its own within a few weeks, although some species may take months to return. We wrote about how the gut affects vitamin absorption in our article on the microbiome and vitamins.

Do probiotics help after antibiotics

Antibiotic diarrhea. A 2012 JAMA meta-analysis of 82 trials found that probiotics cut the risk of this diarrhea by 42%. The result in children is even clearer: in a 2019 Cochrane review (33 trials, over 6,000 children), diarrhea occurred in 8% of children taking a probiotic and 19% of those without one.

Clostridioides difficile. A 2017 Cochrane review (39 trials, nearly 10,000 participants) found that probiotics lowered the risk of C. difficile diarrhea by about 60%, from 4% to 1.5%. In 2020, the American Gastroenterological Association gave a conditional recommendation for certain probiotics to prevent it in people taking antibiotics.

Restoring gut flora. The data here are mixed. In a 2018 study in Cell, people who took a probiotic mix after antibiotics had their own gut flora return more slowly than those who took nothing. The study was small, but the practical takeaway is clear: a probiotic makes sense to prevent diarrhea during the course and for 1-2 weeks after. There is no basis for taking it for months to “repopulate the gut.”

Which probiotic strains have evidence

A probiotic’s effect depends on the strain. Results for one strain can’t be applied to another, even within the same species. So look for the full name on the pack: genus, species and strain code.

In 2020, the genus Lactobacillus was split into 25 genera. The well-known strain Lactobacillus rhamnosus GG is now correctly called Lacticaseibacillus rhamnosus GG. You may see either name on packs; it is the same strain.

For children, the European Society for Paediatric Gastroenterology (ESPGHAN) recommends S. boulardii or L. rhamnosus GG during antibiotics. The Cochrane review found that doses of 5 billion CFU a day or more worked, while lower doses had a weaker effect.

In Ukraine, most probiotics are sold as dietary supplements. We covered the new rules for supplement content and labeling in our article on Ministry of Health Order No. 203. Check whether the CFU count is given for the end of shelf life: bacteria gradually die during storage.

How to take probiotics with antibiotics

When to start. In the first 1-2 days of the antibiotic course. In studies that started the probiotic later, the effect was weaker.

Spacing. Take bacterial probiotics at least 2 hours after the antibiotic dose so it doesn’t kill the bacteria in the stomach. If the antibiotic is taken three times a day, take the probiotic midway between doses. Antibacterial drugs don’t kill S. boulardii, so it can be taken at the same time.

How long. The whole antibiotic course and 1-2 weeks after.

Storage. Some probiotics need refrigeration; the pack will say so. Capsules left in a hot car in summer or on a radiator lose activity quickly.

Diet. During and after the course, fiber helps: vegetables, beans, whole grains, bananas, oatmeal. It feeds your own gut bacteria. More on this in our article fiber vs. probiotics. Kefir and yogurt are fine too, though their bacteria count is unknown.

Who needs probiotics most and who should avoid them

A probiotic with an antibiotic makes the most sense for children, people over 65, those who have had diarrhea after antibiotics or a C. difficile infection, and during broad-spectrum courses. A healthy adult on a 5-day course of amoxicillin often doesn’t need one, though it won’t hurt.

Children. Antibiotic diarrhea is more common in children than adults, especially under 2. ESPGHAN advises L. rhamnosus GG at 10-20 billion CFU a day or S. boulardii at 250-500 mg a day. Drops or sachets are easier for little ones. A capsule can be opened and mixed with a spoonful of cool food or water, because hot food kills the bacteria.

People over 65. They have a higher risk of C. difficile, especially in hospital and after several antibiotic courses. If someone has already had this infection, discuss a probiotic for the next course with a doctor in advance.

Be careful with probiotics in severe immune deficiency, during chemotherapy, after transplantation or with a central venous catheter. There are reported cases of S. boulardii entering the blood through a catheter. That is why in hospitals probiotic capsules are opened away from patients with catheters.

Another caution concerns acute pancreatitis. In the Dutch PROPATRIA trial in 2008, patients with severe pancreatitis who received probiotics through a feeding tube died more often. This is a special group, but it shows that probiotics are not neutral for everyone.

As a pharmacist, I’ll add one more thing: the best way to prevent antibiotic diarrhea is to take antibiotics only when a doctor prescribes them. Taking them on your own for a cold harms both your gut and the wider problem of antibiotic resistance.

When diarrhea after antibiotics needs a doctor

Mild diarrhea during the course usually settles within a few days after it ends. See a doctor if:

you have loose stools more than 3 times a day for over 2 days; there is blood or mucus in the stool; your temperature is above 38 °C (100.4 °F); you have severe abdominal pain; the diarrhea started days or even weeks after the course ended; you have signs of dehydration (dry mouth, little urine, weakness).

In this case a doctor may order a test for C. difficile toxins. Drugs that slow the bowel, such as loperamide, should not be taken on your own if this infection is suspected. And if you have bloating after the course, we have a separate article on that.

Questions and answers

Conclusions

Probiotics roughly halve the risk of antibiotic diarrhea and lower the risk of C. difficile infection. Children, older adults and people on broad-spectrum antibiotics benefit most.

Choose a probiotic with the full strain name: Saccharomyces boulardii CNCM I-745 and Lacticaseibacillus rhamnosus GG have the most evidence. The dose should be at least 5 billion CFU a day.

Take a bacterial probiotic 2 hours after the antibiotic; S. boulardii can be taken with it. Start in the first days of the course and continue for 1-2 weeks after. Severe diarrhea, blood or fever need a doctor.

About the Author

Kateryna Braitenko is a Ukrainian journalist and author specializing in writing articles for pharmaceutical publications. She holds a philology degree from Donetsk National University and a pharmaceutical degree from the National Pharmaceutical University in Kharkiv. She lives in Kyiv and continues her career, covering relevant issues in medicine and pharmaceuticals.