A creatinine test is often part of the blood tests ordered to check kidney function. However, once you are given a laboratory report, you may ask yourself, "So what does it mean for a person this age?
Conversely, it's helpful to know what the normal creatinine level is by age so you can gain some perspective when interpreting a lab report. Creatinine results should not be used alone as it can be influenced by other factors such as muscle mass, age, gender, hydration status, medication and overall health.
Creatinine is a waste product that is made naturally in the body by the muscles. Creatinine is excreted by the healthy kidneys from the blood via urine.
As the function of the kidneys slows down, creatinine can build up in the blood. This is why doctors might sometimes use creatinine as part of an examination of your kidney function.
But a creatinine blood test isn't a full picture of kidney function.
Muscle mass contributes to part of the production of creatinine. Levels may vary by age group because of the differences in muscle mass that can occur among children, adults and older age groups.
Thus, it may not be a good idea to compare the outcome of one individual to one universal value.
Relevant blood tests, medical history, blood pressure, medications, and urine tests may also be taken into account by healthcare professionals, along with creatinine and estimated glomerular filtration rate (eGFR).
These reference ranges may vary between laboratories, and each laboratory will provide a reference range when reporting results.
There are other factors besides age. Sex and muscle mass can also affect creatinine concentration. A muscular person might have a higher creatinine level but not the same kidney-function status, as compared to a leaner person.
Likewise, a creatinine level which seems normal for an older adult with less muscle mass may warrant a further assessment of kidney filtration.
That's why health professionals tend to rely on eGFR and other indicators instead of just creatinine.
Creatinine may be affected by several factors: