Scientists have discovered how long antibiotics affect the body

The results are published in the journal Nature Medicine.

The study was conducted by an international team of scientists led by experts from Uppsala University in Sweden.

The researchers studied data from 14,979 Swedish adults. They compared information on antibiotic prescriptions with analyses of the participants' gut microbiome - the community of bacteria living in the gut.

The details

It turned out that even years after treatment, the composition of bacteria can differ between people who took antibiotics.

According to the authors of the study, traces of the effects of some drugs persist for four to eight years.

And in some cases, the impact left even one course of treatment.

The scientists found that the degree of influence depends on the type of antibiotic.

The most noticeable changes in the microbiome were associated with the use of:

• clindamycin
• fluoroquinolones
• flucloxacillin.

In contrast, penicillin V, one of the most common antibiotics, caused weaker and more short-lived changes.

Why it matters

The gut microbiome plays an important role in the body. It's involved in

• digestion
• immune defence
• metabolism.

Previous studies have linked frequent antibiotic use to an increased risk of certain diseases, including type 2 diabetes and intestinal infections.

The new findings help to better understand why such links may occur.

Background

Scientists emphasise that antibiotics remain vital drugs for treating serious infections. However, their long-term effects on the microbiome are worth considering when prescribing treatment.

Source

Gabriel Baldanzi et al, Antibiotic use and gut microbiome composition links from individual-level prescription data of 14,979 individuals, Nature Medicine (2026), DOI: 10.1038/s41591-026-04284-y