You have been taking antibiotics for a sore throat, but after two days you feel better – except that the tablets make you feel sick. So must you keep taking them? Traditional wisdom is that failing to finish the course allows some bacteria to survive. These will be the hardier ones that can resist the same antibiotic should they meet it again. So for your own good, and that of antibiotic resistance worldwide, you should keep taking the tablets.

But last week, in an article in the Medical Journal of Australia, Professor Gwendolyn Gilbert of the University of Sydney wrote: “There is a common misconception that resistance will emerge if a prescribed antibiotic course is not completed.” She argued that there was minimal risk in stopping antibiotics if the signs and symptoms of a mild infection had resolved.

Professor Chris Del Mar, professor of public health at Bond University in Queensland, agreed, saying that, for most acute chest and urine infections, GPs should tell patients to stop taking the tablets once they feel better. Only for some conditions, such as tuberculosis or osteomyelitis, and other deep-seated infections where symptoms could improve even though the bacteria might still be flourishing, should patients continue taking antibiotics until they have finished the course or their doctor tells them otherwise. People who have problems with their immune system should also stick to the doctor’s advice.

But should most of us go against decades of medical advice and stop taking antibiotics once we feel better?

The solution

It’s complicated. It depends what you have been given antibiotics for. Gilbert says that stopping them prematurely will not directly increase the risk of resistance – that more commonly happens with prolonged treatment on suboptimal doses. In many cases, she says, our bodies can mop up any leftover bacteria. And as many people with respiratory tract infections don’t need antibiotics in the first place, because the infection is not actually caused by bacteria, stopping them is perfectly safe.

Antibiotics change the normal gut flora very quickly – wiping out the indigenous, harmless bacteria and leaving the patient susceptible to resistant bacteria such as Clostridium difficile. “So for individual patients,” says Gilbert, “the less antibiotic they are exposed to, the better.”

Doctors vary in the length of antibiotic regimes they prescribe, with five-day courses for urinary tract infection still being used even though the evidence shows that two to three days is sufficient for an uncomplicated infection.

So if you are given an antibiotic, first ask your doctor if you really need it, and then if you can stop taking it when you feel better. It is too complicated a question (depending, as it does, on the infection and your medical history) to answer with a simple yes.