Creatinine 90umol/L is within the normal range and usually does not cause some harm to the organism. However, whether there is any harm or not should be based on the patient’s medical history, clinical manifestations and glomerular filtration rate. Creatinine is the metabolic end product of creatine in muscle tissue. Creatinine does not combine with protein in the blood and can pass freely through the glomerulus, which is the most commonly used indicator to indirectly reflect the glomerular filtration function. When glomerular filtration is impaired, the body’s serum creatinine may be elevated, suggesting the presence of renal insufficiency. Normal serum creatinine ranges from 53 to 106 μmol/L for men and 44 to 97 μmol/L for women. 90 μmol/L creatinine is a normal creatinine value, which is usually not harmful. Although creatinine 90μmol/L is within the normal range, it does not completely mean that the kidneys are free of diseases, such as nephritis, kidney stones, pyelonephritis, etc., and the blood creatinine of patients with these diseases can often be normal as well. Therefore, in order to clarify whether there is any problem in the kidney, it is necessary to combine with other examinations such as routine urinalysis and ultrasound of the urinary system to make a comprehensive judgment. If patients find abnormal creatinine, it is recommended to go to regular hospitals in a timely manner, improve the examination to clarify the cause of the disease, and then give targeted treatment or therapy under the guidance of doctors.