Taking numerous courses of antibiotics may cause more serious infections, leading to a higher risk of hospital admissions, according to a study.
The study, published in the journal BMC Medicine, is based on the data of two million patients in England and Wales.
Patients who have had nine or more antibiotic prescriptions for common infections in the previous three years were 2.26 times more likely to go to hospital with another infection in three or more months, according to the researchers from the University of Manchester in the UK.
The patient records, from 2000 to 2016, covered common infections such as upper respiratory tract, urinary tract, ear and chest infections, and excluded long term conditions such as cystic fibrosis and chronic lung disease.
It not clear why hospital admissions are linked to higher prescriptions, the team said, adding more research is needed to show what or if any biological factors exist.
The risks of going to hospital with another infection were related to the number of the antibiotic prescriptions in the previous three years, according to the researchers.
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A course is defined by the team as being given over a period of one or two weeks.
"GPs care about their patients, and over recent years have worked hard to reduce the prescribing of antibiotics, said Professor Tjeerd van Staa from the University of Manchester.
"But it is clear GPs do not have the tools to prescribe antibiotics effectively for common infections, especially when patients already have previously used antibiotics, said van Staa.
Researchers said doctors may prescribe numerous courses of antibiotics over several years, which according to the study increases the risk of a more serious infection.
"That in turn, we show, is linked to hospital admissions," van Staa said.
"We don't know why this is, but overuse of antibiotics might kill the good bacteria in the gut (microbiota) and make us more susceptible to infections, for example," he added.
Prescribing antibiotics for a common infection, even though it's not certain whether it's viral or bacterial, might be easier when there is little time, the researchers noted.
"GPs often have little time to get to grips with the detail of a patient's history," said Francine Jury, also from The University of Manchester.
"But what makes it even more difficult is that little official guidance exists for patients who already in the recent past had several courses of antibiotics for common infections," Jury said.