Many of us pop a painkiller without a second thought.

But now scientists are warning the efficacy of the medication could not only depend on the dose or the time of day - but your sex. This is because hormones and genes affect how the body metabolises drugs.

Now, in a new paper, they have revealed women are prescribed drugs that may have never been specifically tested on females.

They explain females are excluded from clinical trials under the assumption that 'one size fits all'.

It is believed a new painkiller or antidepressant will be equally effective in either sex.

But a growing number of scientists say hormones and genetic differences affect how medicines behave in the body - meaning drugs might affect women differently to men.

Writing in the journal Cell Metabolism, experts said both men and women must be accounted for in trials to move medical advances forward.