In order to prevent the occurrence of transplantation rejection, all kidney patients need to take long-term immunosuppressants after surgery. Insufficient dosage will lead to the occurrence of transplantation rejection, while overdose will lead to: 1) increased incidence of cardiovascular and endocrine system diseases such as hypertension, hyperlipidemia and hyperglycemia; 2) significant decrease in immunity, leading to increased risk of infection and malignancy; 3) toxic damage to the transplanted kidney. Therefore, all kidney patients need to use immunosuppressants reasonably under the guidance of kidney transplant physicians. So, how to evaluate whether the dose of immunosuppressant use is just right? At present, the most commonly used main reference index in clinical practice is the drug concentration of immunosuppressants in blood (referred to as blood concentration). The time point for detecting the blood concentration of commonly used immunosuppressants: 1, cyclosporine A (neo-sandimin, neo-serpin): detect the peak concentration 2 hours after taking the drug (peak concentration C2); 2, tacrolimus (Pulcolax, etc.): detect the trough concentration before taking the drug (trough concentration C0); 3, sirolimus (Repamycin): detect the trough concentration before taking the drug (trough concentration C0); 4, mycophenolate esters (primaquine (C0); 4) Mycophenolate esters (primaquine, cycloheximide): detect the concentration at three points before, half an hour after, and 2 hours after taking the drug, and then use the formula for calculation to assess (because there is no recognized better time point and formula for testing Miff, routine testing has not been carried out in the clinic yet). During hospitalization, kidney patients can have their blood drawn and tested almost any time, so they may not give much thought to the appropriate time point for each immunosuppressive drug.