Guide
How much acidophilus should you take a day?
Acidophilus dose is set strain by strain in CFU, not a universal RDA — human trials of named strains have used 10 billion to 200 billion CFU a day.
There's no single established daily dose of acidophilus for adults. Unlike a vitamin or mineral, a live-bacteria supplement doesn't have a U.S. RDA or upper limit — dose is set strain by strain, product by product, and reported in colony-forming units (CFU), not milligrams. Human trials of specific named strains have used doses from about 10 billion to 200 billion CFU a day.
Why there's no single number
Vitamins and minerals have dietary reference intakes because the body has a defined requirement for them. A bacterial strain doesn't work that way: two acidophilus products can list the same species and wildly different CFU counts, use different strains, and be tested (if tested at all) in different trials at different doses. The dose that matters is the one printed on the label of the specific product you're taking, at the strain it names — not a general "acidophilus dose."
What the trials actually used
| Strain | Dose tested | Duration |
|---|---|---|
| L. acidophilus DDS-1 (alone) | 10 billion CFU/day, once daily | 4 weeks |
| L. acidophilus NCFM (alone) | 4×10¹⁰ CFU/day, split twice daily | 21 days |
| L. acidophilus NCFM + B. lactis Bi-07 (combination) | 2×10¹¹ CFU/day, split twice daily | 8 weeks |
These are the doses three specific trials used for specific strains and outcomes — see acidophilus benefits: what the research does and doesn't show for what each one found. None of them establishes a "correct" dose for acidophilus generally; they only tell you what was tested for that strain.
Reading a label's CFU count
Look for two things on a probiotic label: which strain it contains (a species name alone, like "Lactobacillus acidophilus," tells you less than a strain code like NCFM or DDS-1) and whether the CFU count is guaranteed through the end of shelf life or only measured at the time of manufacture — potency can decline in storage, and a label that specifies "at expiration" is describing what you'll actually get when you take it. Milligram figures on some labels (100 mg, 175 mg) describe the mass of the bacterial powder in the capsule, not the CFU count directly — two products at the same milligram weight can contain very different numbers of live organisms.
Is there a dose for taking it with antibiotics?
No trial establishes a specific acidophilus dose for use alongside antibiotics. See acidophilus and medications: what to check for what the evidence around antibiotics actually shows.
Questions people ask
How much acidophilus should I take?
Follow the label of the specific product and strain you're using — there's no general figure that applies across products. If a product doesn't name a strain, there's also no published trial to compare its dose against.
How much acidophilus should I take daily?
Whatever a specific product's label directs. The trials above used daily doses from 10 billion to 200 billion CFU, but each was testing one particular strain, not acidophilus as a category.
How many acidophilus can I take a day?
There's no established maximum. The DDS-1 trial above reported no adverse events at 10 billion CFU/day for 4 weeks, but that's a finding about one strain at one dose over one study length — not a general safety ceiling. See acidophilus side effects for what's actually been reported.
How much acidophilus is too much?
Nothing in the trials reviewed here identifies a specific CFU count where problems start. If you experience new digestive discomfort after starting a higher-CFU product, that's worth mentioning to a doctor rather than guessing at a ceiling.
How much acidophilus is in yogurt?
There's no way to answer that precisely for a given cup. Regular yogurt with "live and active cultures" isn't required to state a CFU count on its label the way a supplement is, so a yogurt serving can't be compared directly to a labeled capsule dose.
How often should I take acidophilus?
The trials above used once-daily (DDS-1) or twice-daily (NCFM) schedules, each specific to that trial's product. Follow the frequency on the label of the product you're actually taking.
Related reading: what is acidophilus, when to take acidophilus, and how to choose a good acidophilus supplement.
Sources
- The effects of the DDS-1 strain of lactobacillus on symptomatic relief for lactose intolerance - a randomized, double-blind, placebo-controlled, crossover clinical trial A small crossover trial found the DDS-1 strain of L. acidophilus, at 10 billion CFU a day for 4 weeks, reduced diarrhea, cramping and vomiting during a lactose challenge, with no adverse events.
- Probiotic bacteria Lactobacillus acidophilus NCFM and Bifidobacterium lactis Bi-07 versus placebo for the symptoms of bloating in patients with functional bowel disorders: a double-blind study A two-strain combination of L. acidophilus NCFM and B. lactis Bi-07, at a combined 2x10^11 CFU/day for 8 weeks, reduced bloating versus placebo in adults with functional bowel disorders — but this tested two species together, not acidophilus alone.
- Lactobacillus acidophilus NCFM affects colonic mucosal opioid receptor expression in patients with functional abdominal pain - a randomised clinical study A small human trial found the NCFM strain of L. acidophilus alone changed a pain-related receptor in colon tissue, but the trial was too small to say whether it actually improved symptoms.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.