Long-term or abusive use of analgesics such as ibuprofen can cause chronic interstitial nephritis, according to the National Kidney Foundation. Interstitial nephritis occurs when the spaces between kidney tubules become inflamed, impairing kidney functionality, states MedlinePlus. It can be either acute or chronic.
Individuals with pre-existing kidney disease should speak to a doctor for confirmation on whether or not they can safely take analgesics, recommends the National Kidney Foundation. This is because analgesics reduce blood flow to the kidneys. Additionally, higher dosages of aspirin can cause heavier bleeding. Individuals should not take over-the-counter analgesics for more than 10 consecutive days for pain. This figure drops to three for fevers. Pain or fever that extends beyond this period requires medical attention. Doctors consider aspirin within the dosage range of 81 to 162 milligrams safe even for patients with impaired kidney function. The safest analgesic for patients with impaired kidneys is acetaminophen as it is less likely to cause complications with bleeding.
The blood test known as a serum creatinine level is helpful for determining if a patient has impaired kidney function due to analgesics, states the National Kidney Foundation. When the kidneys are not functioning correctly, higher levels of creatinine are present within the blood. The other data found in this blood test indicate the patient's glomerular filtration rate, which estimates how much kidney functionality is present. Simple urine tests can also determine kidney health, as higher levels of protein in urine are generally abnormal.