Low creatinine levels in urine are an area of concern when coupled with high creatinine levels in the blood, often indicating disease or malfunction of the kidneys or severe muscle loss due to disease, states the National Institutes of Health. Other possible causes are severe dehydration or urinary tract obstruction.
Creatinine is a waste by-product that is created when muscles break down and metabolize creatine, reports the Mayo Clinic. Creatinine is filtered from the blood by the kidneys and excreted through the urine. The level of creatinine in the urine is one factor in the creatinine clearance test and is key to calculating a patient's glomerular filtration rate, the rate at which the kidney produces clean creatinine-free blood.
In order to ensure proper results for the creatinine clearance test, it is important for the patient to follow a few basic guidelines prior to the test, recommends WebMD. First, a patient should abstain from strenuous exercise for at least 48 hours. It is also important to avoid coffee, tea or other diuretics, so that the urine is not diluted. Diluted urine skews the test and causes inaccurate results. A patient should also eat less than 8 ounces of meat or other protein beginning 24 hours prior to the start of testing. Meat, especially beef, contains additional creatinine and may impact the levels that are naturally occurring in the patient.