Creatinine is the end product of creatine metabolism in muscle tissue. Under conditions of controlled exogenous intake and muscle activity, the production of blood creatinine and excretion of urinary creatinine are relatively constant. Creatinine is mainly excreted through glomerular filtration, so an increased serum creatinine level indicates impaired glomerular filtration, which is one of the main bases for diagnosing renal damage in hypertension. The Chinese Guidelines for the Prevention and Treatment of Hypertension stipulate that a mild increase in serum creatinine, 115-133umol/L (1.3-1.5mg/dl) in men and 107-124umol/L (1.2-1.4mg/dl) in women, is an indicator of target organ damage; serum creatinine >133umol/L (1.5mg/dl) in men and >124umol/L (1.4mg/dl) in women. 1.4mg/dl) is considered renal insufficiency and is classified as renal disease. Of course some hypertension caused by substantial renal disease will show elevated blood creatinine.