Best Probiotic (2026): Strains, Research and Cost Per Day Compared
Each probiotic works only for what its strain was tested for. For a course of antibiotics or a trip, buy Florastor: its strain, S. boulardii CNCM I-745, has the best adult trials for both, at $1.93 a day for 2 capsules at the brand’s price. For a daily one, Culturelle is cheaper and on a testing list.
By Erin Rose Updated October 19, 2026 How we rank
Brand prices, checked October 19, 2026.
Our pick for: Antibiotics and travel
Florastor
First of the 7 we compare: the strain with the most adult trials for antibiotics and travel
- Strain
- S. boulardii CNCM I-745A probiotic yeast
- Amount
- 250 mg a capsuleLabel: 2 capsules, 1 to 2 times a day
- A day
- $1.932 capsules; $3.86 at 4
- Best for
- Antibiotics, travelWhere its trials are
- Storage
- Room temperatureNo fridge needed
- Testing list
- Not on a testing listFor one that is, see Culturelle below
Why we pick it In adults on antibiotics, S. boulardii cut diarrhea from 17% to 8% across 15 trials, and it lowered the risk of traveler’s diarrhea. Florastor’s label names CNCM I-745, the strain from the travel trials.
What you give up It costs more a day than most, and its trials are for diarrhea, not vaginal health or IBS: those need other strains.
Which probiotic is right for you?
Pick by what you want it for. Each of these holds the strain from the trials for that goal.
Want one to take every day, or for a child?
Culturelle Digestive Daily holds LGG, which cut diarrhea from antibiotics in children’s trials and lowered infections in children in hospital. It is on USP Verified, a public testing list, and costs $0.60 a day. We found no strong trials showing a benefit for healthy adults, so a daily probiotic is a choice, not a need.
Culturelle Digestive Daily
$0.60 a day · LGG, 10 billion CFU · USP Verified
For vaginal health?
Take a probiotic with GR-1 and RC-14, the two strains with oral trials for vaginal flora. Jarrow Fem-Dophilus has 5 billion CFU of the two together, counted to the best-by date. Keep it in the fridge. More on vaginal health.
Jarrow Fem-Dophilus
$0.93 a day · GR-1 + RC-14, 5 billion CFU
For IBS or bloating?
Align holds B. infantis 35624, the strain in the best-known IBS trial, where 100 million CFU a day helped. Align has 1 billion when made but promises only 10 million by the best-by date, a tenth of the dose that worked, so a fresh box matters. More on bloating.
Align
$1.08 a day · B. infantis 35624
Probiotics we compared, ranked
Our pick first, then the pick for each goal, then the rest by cost a day at the brand’s own price. Schiff is priced from a 60-capsule bottle at Vitacost because the brand has no store.
| Probiotic | Cost a day | Why it is or is not a pick |
|---|---|---|
| FlorastorS. boulardii, 2 capsules | $1.93 | Our pick: the adult antibiotic and travel trials |
| Culturelle Digestive DailyLGG, 1 capsule | $0.60 | LGG for children; USP Verified |
| Jarrow Fem-DophilusGR-1 + RC-14, 1 capsule | $0.93 | GR-1 + RC-14 for vaginal health |
| AlignB. infantis 35624, 1 capsule | $1.08 | The IBS trial strain; 10 million promised by best-by |
| Schiff Digestive AdvantageB. coagulans, 1 capsule | $0.36 | B. coagulans; one small IBS trial |
| Visbiome8 strains, 1 capsule | $1.22 | 8 strains, 112.5 billion CFU; keep in the fridge |
| Seed DS-0124 strains, 2 capsules | $2.00 | 24 strains; the brand cites its own trials |
What the trials found
Probiotic results belong to the strain tested and the problem it was tested for; a review of 228 trials found that strains of the same species did not share results (McFarland 2018). The strongest results are for diarrhea from antibiotics. In adults, S. boulardii cut it from 17% to 8% across 15 trials (Szajewska 2015, S. boulardii); LGG worked in children (Szajewska 2015, LGG). For IBS, some strains seemed to help, but which ones work is unclear (Ford 2018). Schiff’s B. coagulans had one trial in 44 people with IBS, too small to be sure of (Hun 2009).
More by goal: travel, vaginal health, bloating, immune support, and third-party tested.
Who should ask a doctor first
Ask your doctor first if you are seriously ill, have a weak immune system, or are pregnant: rare blood infections, including with probiotic yeast such as S. boulardii, have been reported in people who were already ill (Hempel 2011). Florastor contains a little lactose. Antifungal medicine can kill S. boulardii.
Questions people ask
How long do probiotics take to work?
It depends on the goal: during the course for antibiotics, every day of a trip for travel, and about 4 weeks in the IBS trial. See how long probiotics take.
Do probiotics need to be refrigerated?
Only if the label says so. Florastor, Culturelle and Align do not; Jarrow Fem-Dophilus 5B and Visbiome do.
How many CFU do I need?
The amount the trial for your strain used, usually 1 to 10 billion a day. More is not always better. See the dosage guide.
Should I take a probiotic with antibiotics?
It can lower your chance of diarrhea. In adults, S. boulardii cut it by about half in trials. Take it during the course. See probiotics with antibiotics.
Do probiotics have side effects?
In trials that reported them, side effects were no more common than on a placebo, though many trials reported harms poorly (Hempel 2011). Some people get gas or bloating at first.
Is Seed worth the price?
Seed DS-01 costs $2.00 a day and names its 24 strains. Its trials are the brand’s own. For a goal with outside trials, a single-strain product costs less. See Seed alternatives.
How we rank
Two things, in order: how strong the trials are for the exact strain on the label, and what a day costs at the brand’s own price. We also checked NSF, USP, Informed Choice and Informed Sport for each product; only Culturelle is on one. We don’t score probiotics out of 10; dose depends on the strain. More on our method.
Sources
- McFarland LV, et al. “Strain-Specificity and Disease-Specificity of Probiotic Efficacy: A Systematic Review and Meta-Analysis.” Front Med (Lausanne). 2018. PubMed 29868585
- Szajewska H, Kołodziej M. “Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea.” Aliment Pharmacol Ther. 2015. PubMed 26216624
- Szajewska H, Kołodziej M. “Systematic review with meta-analysis: Lactobacillus rhamnosus GG in the prevention of antibiotic-associated diarrhoea in children and adults.” Aliment Pharmacol Ther. 2015. PubMed 26365389
- McFarland LV, Goh S. “Are probiotics and prebiotics effective in the prevention of travellers’ diarrhea: A systematic review and meta-analysis.” Travel Med Infect Dis. 2019. PubMed 30278238
- Ford AC, et al. “Systematic review with meta-analysis: the efficacy of prebiotics, probiotics, synbiotics and antibiotics in irritable bowel syndrome.” Aliment Pharmacol Ther. 2018. PubMed 30294792
- Whorwell PJ, et al. “Efficacy of an encapsulated probiotic Bifidobacterium infantis 35624 in women with irritable bowel syndrome.” Am J Gastroenterol. 2006. PubMed 16863564
- Reid G, et al. “Oral use of Lactobacillus rhamnosus GR-1 and L. fermentum RC-14 significantly alters vaginal flora: randomized, placebo-controlled trial in 64 healthy women.” FEMS Immunol Med Microbiol. 2003. PubMed 12628548
- Hojsak I, et al. “Lactobacillus GG in the prevention of nosocomial gastrointestinal and respiratory tract infections.” Pediatrics. 2010. PubMed 20403940
- Hempel S, et al. “Safety of probiotics used to reduce risk and prevent or treat disease.” Evid Rep Technol Assess. 2011. PubMed 23126627
- Hun L. “Bacillus coagulans significantly improved abdominal pain and bloating in patients with IBS.” Postgrad Med. 2009. PubMed 19332970
- Brand pages and labels, read October 19, 2026: Florastor, Culturelle, Jarrow Formulas, Seed, Visbiome; Align and Schiff at Vitacost.