How long does your gut microbiome take to recover after antibiotics?
Depending on the antibiotic, the gut microbiome recovers in 1 week to several months, sometimes without fully returning to where it started. After a very strong course, 12 men went from 160 bacterial species to 73 on day 8, and had 136 after 6 months (Palleja, 2018; Fischer and Bild, 2019).
Where do these bacteria live, what do they eat, and how many are left?
Counts come from stool samples: dot positions are illustrative, see below.
Who lives where, who eats what
Counts come from the stool of 12 men: the study does not say where each species lived. The places and diets come from other studies, cited below. The number of dots follows the counts of 160, 73 and 136; between those days, it is estimated.
| Group | Where it lives | What it eats | What it leaves |
|---|---|---|---|
| Fiber degraders (Bacteroides) | The contents, and part of the loose mucus | Dietary fibers: resistant starch, pectin, xylan, beta-glucan | Shorter sugars and succinate, taken up by other bacteria |
| Bifidobacteria | The contents | Short sugars released by fiber degraders | Lactate, acetate and formate, taken up by other bacteria |
| Butyrate producers (Faecalibacterium, Roseburia) | The contents, up to the edge of the mucus | Acetate and lactate from other bacteria, plus sugars | Butyrate, the main food of the cells lining the colon |
| Mucus eaters (Akkermansia muciniphila) | The loose layer of mucus | The mucus made by our gut lining | Propionate and released sugars, taken up by butyrate producers |
| Enterobacteria (including E. coli) | Near the lining and in the crypts | Simple sugars left free; they breathe the oxygen and nitrate coming from the lining | Their numbers rise when the others are missing |
- humanAlmost all in the colon. About 100 billion bacteria per milliliter in the colon, versus 1,000 to 10,000 in the upper small intestine (Sender, 2016).
- animalTwo layers of mucus. The dense layer, against the lining, has almost no bacteria; the loose layer is their home, and the bacteria in the crypts are not the same as those in the contents. Most of these observations come from mice; in humans, they come from biopsies (Tropini, 2017).
- animalWhy enterobacteria rise. Butyrate feeds the lining cells, which use up oxygen. When butyrate producers are missing, more oxygen and nitrate remain in the gut, and enterobacteria use them to breathe (Olsan, 2017, mostly in mice).
- animalWithout fiber, they eat the mucus. In mice, a fiber-free diet pushes bacteria to eat the mucus and thins the protective layer (Desai, 2016; Tiffany, 2026).
- hypothesisDot positions. Each dot is placed in the zone where its group lives, but its exact position and size are illustrative.
Which bacteria live in the gut, and what do they make?
Bacterial shapes based on how they look under the microscope; sizes and positions are illustrative. Tap a family to go to its step.
The families in text, and where these numbers come from
| Family | Phylum | Share of bacteria | What it eats | What it makes | Where it goes |
|---|---|---|---|---|---|
| Bacteroides (Bacteroidaceae) | Bacteroidota (formerly Bacteroidetes) | About 90% together with Bacillota | Fibers our enzymes cannot digest | Short sugars, acetate, propionate, gas | Propionate to the liver, acetate into the blood |
| Bifidobacteria (Bifidobacteriaceae) | Actinomycetota (formerly Actinobacteria) | 2 to 14% in adults | Short sugars | Acetate, lactate, folate (vitamin B9) | Acetate and lactate taken up by other bacteria |
| Faecalibacterium (Oscillospiraceae), Roseburia (Lachnospiraceae) | Bacillota (formerly Firmicutes) | 3.8% on average for the F. prausnitzii group | Acetate, lactate, sugars | Butyrate, gas | The colon lining, which feeds on it |
| Akkermansia muciniphila (Akkermansiaceae) | Verrucomicrobiota | Over 1% of stool cells | Mucus made by the lining | Propionate, acetate | Liver and blood |
| Enterobacteria, including E. coli (Enterobacteriaceae) | Pseudomonadota (formerly Proteobacteria) | A small minority | Simple sugars left free | Vitamin K2 | The blood; they take the free space when the others are missing |
- humanThe 3 fatty acids. In the colon and stool, acetate, propionate and butyrate are found in a ratio of roughly 60:20:20. 95% are taken up by the body, 5% leave in the stool (den Besten, 2013).
- humanWhat is left after the lining and the liver. Fasting, in patients having gallbladder surgery: in the vein leading to the liver, acetate 128, propionate 34, butyrate 18 µmol/L; in arm blood, acetate 67, propionate 4, butyrate only in traces. Butyrate is held back by the lining, propionate by the liver (Cummings, 1987).
- humanEnergy for the lining. The cells lining the colon get 60 to 70% of their energy from these fatty acids, and butyrate is their main fuel (den Besten, 2013).
- humanGas. 10 volunteers, with 200 g of navy beans added to their meals: 0.5 to 1.5 L per day, 0.7 L median, mostly hydrogen. After 2 days without fiber: 0.2 L (Tomlin, 1991).
- humanThe share of each family. Bacteroidota and Bacillota, about 90% together (Rinninella, 2019); bifidobacteria, 2 to 14% in adults, much more in babies (Arboleya, 2016); the F. prausnitzii group, 3.8% on average in 10 people (Hold, 2003); Akkermansia, over 1% of stool cells (Derrien, 2008); enterobacteria, a small minority (Shin, 2015). These shares vary a lot from person to person.
- humanVitamins. Some gut bacteria, including bifidobacteria, make B vitamins; others make vitamin K2 (LeBlanc, 2013; Conly, 1992).
- hypothesisShapes and positions. The shapes follow how they look under the microscope (rods, the Y of bifidobacteria, the ovals of Akkermansia), but sizes and positions are illustrative: in the gut, these families are mixed together.
How many species remain, day after day?
The drop takes a few days, the recovery a few weeks; only days 0, 8 and 180 are published counts.
How reliable these numbers are, and what is estimated (5 notes)
Do all antibiotics leave the same mark?
No: depending on the drug, the measured difference lasts from 1 week to 1 year. Each bar runs to the last check where a difference was still measured.
The values in text, and how reliable these numbers are (3 notes)
| Antibiotic | Different composition | Lower diversity | Study |
|---|---|---|---|
| Amoxicillin and clavulanic acid | up to 1 week after stopping | not given | MacPherson, 2018 (70 adults) |
| Amoxicillin | 1 week | no clear effect | Zaura, 2015 (14 people) |
| Minocycline | 1 month | right after the course | Zaura, 2015 (10 people) |
| Clindamycin | 4 months | 4 months | Zaura, 2015 (9 people) |
| Ciprofloxacin | 1 month | 12 months | Zaura, 2015 (10 people) |
| Very strong trio | 1.5 months | fewer species at 6 months | Palleja, 2018 (12 men) |
- humanSmall groups. 9 to 14 people per antibiotic in Zaura, all in good health. These durations do not apply to everyone.
- humanA study funded by a manufacturer. MacPherson, 2018 was funded by Lallemand, which sells probiotics.
- humanFrom one person to another. 3 people took ciprofloxacin twice for 5 days. Their diversity fell within 3 to 4 days and mostly came back within 1 week, but at the end of the study, after 10 months, their microbiome was stable and different from the start. The response varied from person to person, and from one course to the next (Dethlefsen and Relman, 2011).
Frequently asked questions about the gut microbiome and antibiotics
How long does it take to rebuild your gut flora after antibiotics?
Gut flora, or the microbiome, recovers in 1 week to several months depending on the antibiotic. After 7 days of amoxicillin and clavulanic acid, it was back to its starting profile 1 week after stopping (MacPherson, 2018). After a much stronger course, it was close to the start within 6 weeks, with some species still missing at 6 months (Palleja, 2018).
Which bacteria live in the gut, and what do they make?
Two large groups, Bacillota and Bacteroidota, make up about 90% of colon bacteria (Rinninella, 2019). Together, they turn the fibers we cannot digest into acetate, propionate and butyrate, in a ratio of roughly 60:20:20, and 95% of these fatty acids are taken up by the body (den Besten, 2013). Butyrate feeds the colon lining, propionate goes to the liver, acetate reaches the muscles. Some also make vitamin B or K2, and gas.
Should you take probiotics after antibiotics?
Not necessarily: they do not seem to help the microbiome come back, but they may lower one specific risk. In a small study, the original microbiome returned more slowly and less completely with probiotics (Suez, 2018). Against C. difficile infection, a large review found 1.5% of cases with probiotics versus 4.0% without; the benefit shows mainly when the starting risk is above 5%, not below (Cochrane, 2025). Talk it over with a doctor or pharmacist.
Why can antibiotics cause diarrhea?
An antibiotic also kills helpful gut bacteria, and others can then take their place. The most feared one is called C. difficile: the risk can be up to 10 times higher during the course and in the month after (CDC). Severe or lasting diarrhea calls for a doctor's visit.
What should you eat to help your microbiome after antibiotics?
None of the studies on this page compares diets after an antibiotic, so it cannot recommend a specific food. We do know, though, that the microbiome reacts quickly to diet: it changed one day after the new diet reached the gut, in 10 volunteers per diet (David, 2014).
See also
Do antibiotics work against viruses? What is gastritis and how long does it last? How does an ulcer form and how does it heal?
Sources
- Palleja A et al. Nature Microbiology, 2018. doi:10.1038/s41564-018-0257-9
- Fischer MM, Bild M. Preprint, 2019. arXiv:1906.11546
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- MacPherson CW et al. Scientific Reports, 2018. PMC6060159
- Dethlefsen L, Relman DA. PNAS, 2011. doi:10.1073/pnas.1000087107
- Suez J et al. Cell, 2018. doi:10.1016/j.cell.2018.08.047
- Esmaeilinezhad Z et al. Cochrane, 2025. CD006095
- CDC. About C. diff
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True or false?
All antibiotics harm the microbiome for months.
False. The mark depends on the drug: in 14 people on amoxicillin, the composition differed from placebo only at 1 week; on clindamycin, up to 4 months (Zaura, 2015).
Probiotics always speed up the microbiome's recovery.
False. In a small study, the original microbiome came back more slowly and less completely with probiotics (Suez, 2018).
The same antibiotic can act differently in two people.
True. In 3 people who took the same ciprofloxacin, the changes varied from person to person, and from one course to the next (Dethlefsen and Relman, 2011).
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Metabolive. "How long to recover gut flora after antibiotics?" Updated November 2, 2026. https://metabolive.com/en/everyday/gut-microbiome-antibiotics.