The causes of low creatinine levels include chronic conditions that lead to declines in creatinine production along with declines in muscle mass. Having lowered creatinine levels is not necessarily a cause for concern, although if the cause is not readily apparent, a doctor may request some additional medical testing to find out why the levels are low. This testing will be used to determine if a patient has an underlying condition that needs to be treated.
One of the most common causes is loss of muscle mass. This can occur naturally with aging, leading to lower creatinine levels in older adults. It can also be associated with wasting diseases, sudden weight loss, myasthenia gravis, muscular dystrophy, and injuries that force people to take bedrest. Any condition that leads to a decline in muscle mass can result in low creatinine levels.
Another reason can be a low protein diet. Creatinine is produced through the processing of protein and if a patient is eating unusually low levels of protein, the body will be making less creatinine. Pregnancy is also associated with low creatinine levels because of the redirection of nutrients to the baby. Even when a woman is eating a balanced diet with another nutrition for two, the levels of certain nutrients in her blood can be skewed because the developing fetus has such high energy and nutrition demands.
Advanced liver disease is also associated with low creatinine levels. Usually the liver disease is already known when low creatinine levels are observed, but the drop in creatinine levels can be an indicator that the disease is getting worse or that the liver is under stress. A doctor may request a liver enzyme panel, ultrasound examination of the liver, and other testing designed to assess liver function. These tests may show that the approach to treatment needs to be changed or that the patient is in need of a liver transplant.
Creatinine levels are determined with a blood test and lab analysis. Lab technicians will usually provide normal range references with lab results so that the results can be read and interpreted easily. If a doctor notes that creatinine levels are low, the patient's chart will be consulted for any obvious explanations. If nothing in the patient history explains the low levels, the doctor may ask the patient to consent to follow up testing with the goal of learning more about why the patient's creatinine levels are dropping.