Antibiotics: Long-Term Impact on Gut Health Revealed in 8-Year Study
Long-Term Gut Microbiome Disruption Linked to Antibiotic Use
Antibiotics, while essential in modern medicine, can disrupt the delicate balance of the gut microbiome for years after treatment, according to a new study published in Nature Medicine. Researchers at Uppsala University in Sweden have found that changes in the composition of gut bacteria can persist for as long as eight years following antibiotic use.
The study, which analyzed data from nearly 15,000 adults in Sweden, linked prior antibiotic exposure to alterations in the diversity and composition of the gut microbiome. Researchers combined antibiotic prescription data from the Swedish Drug Register with detailed microbiome analyses from biobanks at Uppsala and Lund Universities. The findings highlight the long-lasting impact of these medications on the complex ecosystem within the human gut.
The gut microbiome, comprised of trillions of microorganisms, plays a critical role in digestion, metabolism and immune function. Antibiotics, designed to eliminate harmful bacteria, inevitably affect beneficial bacteria as well, disrupting this intricate balance. While previous research demonstrated short-term impacts of antibiotics on the gut microbiome, the duration of these effects remained largely unknown.
“We can see that antibiotic use as far back as four to eight years ago is linked to the composition of a person’s gut microbiome today. Even a single course of treatment with certain types of antibiotics leaves traces,” said Gabriel Baldanzi, the study’s first author and a former doctoral student at Uppsala University.
The research examined eleven classes of antibiotics. Six of these were associated with reduced bacterial diversity when administered in the year prior to sample collection. While the most significant impact occurred within the first year, detectable changes remained even after four to eight years. The microbiome demonstrated some initial recovery, but did not fully return to its original state, researchers found.
The effects varied depending on the specific antibiotic used. Penicillin V, commonly prescribed for throat and tonsil infections, showed minimal and short-lived effects. However, other antibiotics, such as tetracyclines – used for respiratory and urinary tract infections – were linked to more prolonged shifts in the microbiome.
Notably, clindamycin, fluorochinolones, and flucloxacillin exhibited the most substantial and lasting impacts. These antibiotics are often reserved for situations where other treatments have failed, highlighting the potential for prolonged disruption even with limited use. A study published by scinexx.de on March 16, 2026, noted that the strong effect of flucloxacillin on the gut flora was “unexpected.”
Researchers emphasize that antibiotics remain vital for treating bacterial infections. However, the findings underscore the necessitate for more judicious antibiotic use and a greater understanding of their long-term consequences.
“We believe that the results of our study can contribute to improving future recommendations for antibiotic use, especially when choosing between two equally effective antibiotics, one of which has a lesser impact on the gut microbiome,” explained Tove Fall, an epidemiologist and co-author of the study.
The study does not offer immediate clinical guidance, but provides further evidence of the complex relationship between antibiotic use and long-term health. Further research is needed to fully understand the clinical implications of these microbiome alterations and to develop strategies to mitigate their effects.