A blood test may help people who overdose on paracetamol as it shows quickly if they are at risk of suffering liver damage, says a study. The test – which detects levels of specific molecules in blood – could help doctors identify which patients arriving in hospital need more intense treatment.

Paracetamol is a relatively safe painkiller when taken in the right dose. But many people unknowingly consume too much by taking paracetamol at the same time as cold and flu medications that also contain the drug. Liver injuries are a common complication of drug overdoses. In some cases the damage can be so severe that the patient needs a transplant and, in rare instances, can be fatal.

“Paracetamol overdose is very common and presents a large workload for already over-stretched emergency departments. These new blood tests can identify who will develop liver injury as soon as they first arrive at hospital. This could transform the care of this large, neglected, patient group,” said one of the researchers James Dear of the University of Edinburgh in Britain.

The study, published in the Lancet Gastroenterology & Hepatology, showed that the test can accurately predict which patients are going to develop liver problems, and who may need to be treated for longer before they are discharged. The test detects three different molecules in the blood that are associated with liver damage – called miR-122, HMGB1 and FL-K18.

The researchers measured levels of the three markers in more than 1,000 patients across the UK who needed hospital treatment for paracetamol overdose.

They found that it could identify patients at risk of suffering liver damage. The test could also help identify patients who could be safely discharged after treatment.