Surgery is an important time to be aware of the potential risks of herbs. The many drugs used before, during, and after surgery increase the risk of potential herb-drug interactions. Some herbs promote bleeding by reducing how quickly the blood clots, which may be useful for a painful arthritic joint perhaps, but not ideal for the operating table. Herbs may also alter the way various drugs used in and around surgery are metabolised (anaesthetics, painkillers, antibiotics, etc).