Tacrolimus is an immunosuppressive drug that is believed to prevent rejection in transplantation patients. Measurement of tacrolimus blood levels may be of use in monitoring patients receiving this drug. The level of tacrolimus in the blood must be maintained within a narrow therapeutic range. If the concentration is too low, organ rejection may occur; if it is too high, then the person may experience symptoms associated with toxicity. Prograf weakens your body's immune system, to help keep it from rejecting a transplanted organ such as a kidney. Organ rejection happens when the immune system treats the new organ as an invader and attacks it. Your healthcare provider may do blood tests to check your potassium level. high blood pressure. High blood pressure is a serious and common side effect of PROGRAF. Your healthcare provider will monitor your blood pressure and may prescribe blood pressure medicine for you, if needed. Your healthcare provider may instruct you to check your blood pressure at home. changes in the electrical. Blood levels still low on blood counts, liver functions trending back toward the normal range. I guess the increase in Prograf helped. Biopsy showed no indication of rejection. Measuring the level of medicine in your blood helps your doctor to prescribe you the correct dose. If you get diarrhoea during treatment, this can affect the amount of medicine in your blood and extra monitoring of your tacrolimus blood level is recommended. Your healthcare provider may do blood tests to check your potassium level. high blood pressure. High blood pressure is a serious and common side effect of PROGRAF. Your healthcare provider will monitor your blood pressure and may prescribe blood pressure medicine for you, if needed. Your healthcare provider may instruct you to check your blood pressure at home. changes in the electrical. In the blood, tacrolimus is mainly bound to erythrocytes; only 5% are found in the plasma, of which more than 98.8% are bound to plasma proteins. [11] [21] The substance is metabolized in the liver, mainly via CYP3A , and in the intestinal wall. The normal reference range for Prograf is 4 - 16 ng/ml. This is so individual that it is hard to know what level is right for anyone without a lot of experience.