Transplantation is the standard therapeutic option for patients with severe heart failure if all other treatment options, including pharmacotherapy and various surgical methods, have been exhausted. Despite the detailed pretreatment and selection that patients undergo before the procedure itself, an immune response to the transplanted organ is inevitable. Therefore, the introduction of immunosuppressants into a lifelong therapy is necessary for successful graft survival. Cyclosporine A (CsA) has emerged as the first choice and core drug in various combinations to prevent rejection. Over the years, significant progress has been made in the development of formulations and improvements in pharmacokinetic parameters, especially absorption, which has become more consistent and faster with consequently increased bioavailability. However, despite these improvements, due to the narrow therapeutic index, serious side effects, and differences in exposure among individuals after oral administration, the need for therapeutic monitoring of blood concentrations (TDM) still existed. A necessary prerequisite that must be met in order to perform TDM is the existence of a correlation between the therapeutic effect and the drug concentration in the blood. The measurement of blood concentrations and dose adjustment based on measured values provided the possibility of an individual approach to each patient and optimization of therapy with the aim of improving treatment outcomes. Despite certain shortcomings, the most commonly used techniques for quantitative determination of drugs in the blood are immunoassays, while liquid chromatography coupled with tandem mass spectrometry is considered the gold standard. Although highly selective, it is not implemented in the routine practice due to the high cost of the analyser and the complex sample pretreatment. Apart from choosing the appropriate method, it is also important to properly take and prepare sample for analysis, storage at the appropriate temperature and choice of the right sampling time. The standard way to monitor cyclosporin blood levels is over the lowest (trough, C0) concentration and it has remained stable in clinical practice over the years. Taking into account pharmacokinetic characteristics of CsA (peak blood concentration is reached 2 h after administration, the maximum degree of inter- and intraindividual differences occur around the absorption phase during the first 4 h after dosing) other parameters such as AUC and concentration at point C2 (2h after oral administration) were studied. C2 values well reflect the degree of immunosuppression and drug toxicity, but despite this, due to the similarity of the results obtained, point C0 is used to monitor CsA and it has proven to be a reliable tool for characterizing drug absorption profiles and individualizing therapy.