PARIS (AFP) ― Scientists have created a molecule that glows red or blue depending on drug levels in blood ― the basis for a prospective home test to prevent patients accidentally overdosing, they reported Sunday.

After contact with a drop of blood, the molecule’s color is observed with the aid of an ordinary digital camera, its Swiss and American developers wrote in the journal Nature Chemical Biology.

“The process does not require any laboratory instruments and is so simple that the patients can do it themselves,” Rudolf Griss from the Swiss Federal Institute of Technology in Lausanne says in a video explaining the invention, which is being refined for commercial use.

People who use medicine for conditions like cancer, heart disease and epilepsy or immunosuppressants to prevent organ rejection after a transplant, risk side effects or even poisoning from overdosage, or the drugs not working if the dose is too small.

But tests to monitor dosage are expensive, time consuming and have to be done by trained experts at a laboratory.