Taking too many painkillers can damage some people's kidneys permanently, scientists claim.
Overuse was defined as taking two doses of full strength aspirin or extra strong paracetamol every day.
The risk only affects people who are susceptible - most people, including cardiovascular patients taking small doses of aspirin - are not at risk.
But doctors told the American Society of Nephrology they had no way of spotting the few who are at risk.
The researchers found that heavy use of aspirin or paracetamol - defined as 300 grams a year - was linked to a condition known as small, indented and calcified kidneys (SICK).
The condition was detected in patients with irreversible kidney failure by carrying out computed tomography (CT) scans.
Changes in the kidneys
Over 200 patients treated for kidney failure across the US were scanned for SICK and asked about their use of painkillers.
Seven per cent were found to have SICK, and a third of those patients had overused analgesics.
Scientists from the National Analgesic Nephropathy Study said: "We conclude that heavy use of analgesics at least nine years prior to the development of irreversible kidney failure is associated with the anatomic changes of small, indented and calcified kidneys."
Dr Vardaman Buckalew, a kidney specialist at Wake Forest University Baptist Medical Center in North Carolina said: "If a patient does have SICK, there is an increased likelihood of analgesic abuse."
He added: "We think just some individuals are susceptible, But there is no way yet to figure out which individuals are susceptible and which aren't."
A spokeswoman for the National Kidney Research Fund told BBC News Online: "Large doses of some analgesics, including aspirin and paracetamol, may depress kidney function in patients who already have kidney disease.
She added: "Extremely large doses of aspirin and paracetamol can cause acute renal failure, usually when taken as a suicide attempt.
"And there is some anxiety that if large doses can cause disease in many subjects, lower doses may cause it in a few subjects.
"The advice is don't take analgesics unless you really need them, take single drugs such as aspirin and paracetamol, carefully study the instructions - and if you have any kidney disease, seek medical advice before taking analgesics."