The Relationship Between Serum Creatinine and Kidney Function

When we go to the hospital and be told that there is something wrong with kidneys, the main indicators to prove damage on kidneys are Urea Nitrogen and SERUM CREATININE, the latter is often be used to be the indicator of kidney function. So it is necessary for us to understand the relationship between serum creatinine and renal function.

The word "serum creatinine" is difficult to understand for many patients with kidney problem, because they do not have much knowledge about nephrology. Let's put it simple, serum creatinine is the break-down products of muscle metabolizing. Creatinine is formed slowly in human muscles by creatine’s irreversible nonenzymic dehydration reaction, and after processing (filtration and excretion) by kidneys, it will be released into blood and finally discharged outside the body though urine. So there is a closed relationship between kidneys and creatinine. In case that daily-produced serum creatinine can not be discharged though urine, then the concentration of serum creatinine will increase, the higher the creatinine is, the worse the renal function will be. However, for some kidney disease patients, although their kidney function is OK, it does not means that there is no problem about kidney function.
There are two kidneys in human body, normally, however, one kidney is enough to meet the physical requirement. That is because kidneys have a strong compensatory capacity. Therefore, some renal failure patients could receive donation of kidney and continue to their life. General speaking, the level of creatinine will rise only when the renal function is already lower than 50% ~ 30%. In other words, if someone found that his/her serum creatinine rises, it means that his/her renal function is already lose more than 50%.

Serum creatinine also has relationship with human's muscle, weight and age, same level of serum creatinine means different for different people. For example, same level of creatinine means OK for Arnold Schwarzenegger (former World Bodybuilding Champion) but means serious problem on kidney for thin, bedridden old man. On the other hand, Serum creatinine may also raise when someone eats a lot of meats, and for the women in middle and end-stage of pregnancy, their serum creatinine will lower. So clinically, creatinine can be converted to Creatinine Clearance Rate to achieve the goal of precise judgment of renal function.