Metformin has been clinically used for more than 50 years and has become the first-line drug of choice for diabetes treatment at home and abroad, but there is less research on metformin in China. Therefore, in clinical practice, some clinicians and patients still have misconceptions about the use of metformin, such as its effectiveness, dose and safety. The following is to explain whether metformin has damage to liver and kidney function, in order to solve the doubts of patients. First, whether metformin will aggravate renal damage Metformin will not aggravate renal damage. People with kidney damage can not use metformin, just because of kidney damage, kidney function excretion disorder, metformin excretion also slowed down, the blood concentration is high, will aggravate the side effects of metformin itself, such as lactic acidosis. So it is not that metformin itself will aggravate the kidney damage. Whether the blood creatinine is elevated or proteinuria occurs, metformin dosing can be adjusted by estimating the glomerular filtration rate (eGFR) level: eGFR>=60ml/(min・1.73m2) can be used safely, eGFR between 45 and 60ml/(min・1.73m2) is used cautiously, eGFR<45ml/(min・1.73m2) Discontinue use. The formula for assessing eGFR applicable to our patients with chronic kidney disease is: eGFR[ml/(min・1.73m2)]=175・Scr-1.234(64mg/dl)・ageScr indicates serum creatinine. In conclusion, metformin should not be used in stage 5 chronic kidney disease, but it can be used in patients with mild to moderate chronic kidney disease. Second, can metformin be used in patients with hepatic impairment Metformin is not metabolized by the liver and has no hepatotoxicity, but severe impairment of hepatic function will significantly limit the clearance of lactate, so it is recommended to avoid the use of serum aminotransferase when it exceeds 3 times the upper limit of normal. Patients with mildly elevated serum aminotransferases are closely monitored for liver function when used, and metformin should not be judged not to be used when elevated aminotransferases are seen. Therefore, in clinical practice, patients should not miss the opportunity to treat some patients who could benefit from metformin therapy because of the fear that metformin will damage liver and kidney function. The dose of metformin should be chosen reasonably with respect to their liver and kidney function to give the most effective effect of metformin.