The creatinine blood test measures the amount of creatinine in your blood. Creatinine is a normal waste product your body makes when you use your muscles and some muscle tissue breaks down; healthy kidneys filter it out of the blood and remove it in urine. Because creatinine is removed from the body almost entirely by the kidneys, its level in the blood is used as a general indicator of how well the kidneys are working. It may be measured on its own or as part of a routine metabolic panel.
A clinician may order this test to check kidney health as part of a routine checkup, to help diagnose or monitor kidney disease, or to watch for side effects of certain medications on the kidneys. It may also be ordered when someone has possible symptoms of kidney disease (per MedlinePlus, these can include swelling, dry or itchy skin, fatigue, changes in how often you urinate, bloody or foamy urine, loss of appetite, muscle cramps, nausea, shortness of breath, trouble sleeping, and trouble concentrating), or for people at higher risk, such as those with diabetes, high blood pressure, heart disease, or a family history of kidney disease.
These figures are general reference values only and are not a personal cutoff or diagnosis. MedlinePlus lists a general normal range of about 0.7 to 1.3 mg/dL (62 to 115 µmol/L) for men and about 0.5 to 0.95 mg/dL (44 to 84 µmol/L) for women, and notes that women often have lower levels because they typically have less muscle mass. What is "normal" for you depends on factors such as muscle mass, body size, diet, age, and activity level. MedlinePlus states that "Normal value ranges may vary slightly among different laboratories," and that some labs use different measurements or test different samples. The reference range printed on your own lab report — and how your clinician interprets it for your age, sex, and health — is what applies to you. A normal result also does not always rule out kidney problems, since levels can stay normal in early kidney disease.
This is a list of general possibilities, not a diagnosis or a complete list. A higher-than-normal creatinine level may be seen with kidney problems such as kidney damage or failure, kidney infection, reduced blood flow to the kidneys, or a blocked urinary tract, and can also be associated with conditions such as heart failure or diabetes. Importantly, MedlinePlus notes that a high level does not always mean a kidney problem — it may also be linked to dehydration, muscle disorders or muscle breakdown, intense exercise, a diet high in meat, or pregnancy-related conditions such as preeclampsia or eclampsia. Only a clinician can interpret what a high result means in your specific situation.
Low blood creatinine levels are less common. When reported, a lower-than-normal level may be associated with malnutrition, with conditions that reduce muscle mass (including muscle or nerve disorders), or with serious liver disease. These are general possible associations, hedged and incomplete — not a diagnosis. A clinician interprets a low result in the context of your overall health.
Reference ranges vary by laboratory, age, sex, and method — the range on your own report is what applies to you. A single value out of range doesn’t confirm any condition; your clinician interprets it alongside your symptoms, history, and other results. This page is general information, not medical advice.
General reference, not medical advice, and not a substitute for your clinician. Lab reference ranges and interpretation depend on the laboratory and on your individual situation — discuss your results with a licensed healthcare professional.