Whether creatinine 138 μmol/L is serious depends mainly on the cause of its elevation. If it is a physiological reason, or acute kidney injury causes creatinine elevation, after removing the influencing factors creatinine may return to normal, at this time is usually not serious. If the elevated creatinine is caused by chronic kidney disease, with the progress of the disease, it may develop into uremia, which is relatively serious at this time. Normal serum creatinine ranges from 53 to 106 μmol/L in men and from 44 to 97 μmol/L in women. Blood creatinine includes endogenous creatinine and exogenous creatinine. Endogenous creatinine is produced by creatine metabolism and is related to muscle volume and muscle activity; exogenous creatinine is closely related to diet, especially the consumption of heated animal muscle may lead to a rapid increase in blood creatinine levels. Therefore, part of the creatinine elevation may be caused by the patient’s own high muscle content, or usually eat more meat and exercise, if the urine routine and urinary system ultrasound and other related examinations do not see any abnormalities, and clear renal disease is not obvious, this kind of situation is usually not serious. When the renal parenchyma is damaged and the glomerular filtration rate is reduced to the critical point (when the glomerular filtration rate is reduced to 1/3 of normal), the blood creatinine will rise significantly. If the patient has acute kidney injury due to various reasons, creatinine may return to normal after correcting the reversible cause. If chronic kidney disease causes elevated creatinine, as the disease progresses, it may develop into uremia, which is relatively serious at this time. If patients find that the blood creatinine is elevated, it is recommended to go to the regular hospital in time, under the guidance of the doctor to give targeted treatment or therapy.