Creatine is a part of the muscles of the body. When creatine breaks down, creatinine is produced. Blood and urine tests determine the amount of creatinine present in blood to assess kidney function.
Creatinine levels in the blood increase with abnormal kidney function because less creatinine is excreted through urine. Body size and muscle mass also play a role in creatinine levels.
Healthy people have creatinine levels checked during routine physical exams, and patients with chronic illnesses have levels checked to gauge progress of treatment methods.
Blood and urine levels of creatinine are measured in combination to see how well the kidneys filter small creatine molecules.
According to Medline Plus, a service of the U.S. National Library of Medicine, creatinine levels between 0.8 and 1.4 mg/dl are normal, although guidelines do vary between labs. A woman will often have lower levels because she has less muscle mass.
High creatinine levels can indicate problems with blood vessels in the kidneys, bacterial infection, cell death in the small tubes of the kidneys, shock or dehydration, muscle injury and urinary tract obstruction problems such as prostrate disease or kidney stones.
Serious problems associated with high levels of creatinine in the blood are diabetes, arthrosclerosis and congestive heart failure.