Sudden dose reduction of targeted drugs can lead to fluctuations in blood concentration, affecting the efficacy of treatment, leading to the early emergence of drug resistance and even serious adverse reactions. The dosage of targeted drugs cannot be self-selected. The frequency and dosage of targeted drugs are derived through repeated animal and clinical trials. Only when taken regularly and according to a certain dosage can a stable blood concentration be achieved and the best therapeutic effect of the targeted drug be realized. Sudden increase or decrease will lead to fluctuation of blood concentration, affecting the therapeutic efficacy and leading to the early emergence of drug resistance and even serious adverse reactions. Targeted drugs should be taken regularly and quantitatively, which is more conducive to stabilizing the blood concentration. When the side effects of taking targeted drugs are large, it is necessary to communicate with the doctor and follow the doctor’s advice to regulate.