BACKGROUND: During the coronavirus disease 2019 (COVID-19) pandemic, significant challenges have been encountered in managing patients with chronic diseases. This study aimed to evaluate the effects of the pandemic on follow-up and treatment adherence in patients receiving immunoglobulin replacement therapy (IRT). METHODS: A study examining the changes in IRT application methods was conducted between March 2020 and September 2021. An online message line, under the control of nurses and doctors, was established for our patients, and their usage rates for this communication system were recorded. RESULTS: A total of 169 patients, 93 males and 76 females, were included in the study. Among the patients, 124 (73.4%) received intravenous immunoglobulin (IVIG), and 45 (26.6%) received subcutaneous immunoglobulin (SCIG) treatment. Male sex was more common in both the IVIG and SCIG groups. Although all patients in the subcutaneous treatment group continued the treatments regularly, this rate was 80.6% in the IVIG group. During the pandemic, 26 patients switched from IVIG to SCIG treatment. Furthermore, 24 patients interrupted immunoglobulin treatment for various reasons. Patients who received subcutaneous treatment took a long break from their hospital controls, although they applied them properly at home. Routine immunoglobulin trough values were measured in only 17 (37.7%) patients who were on SCIG. In the presence of symptoms, 100% of SCIG patients contacted the remote medical team via the online message line, compared to 48.3% of IVIG patients. CONCLUSION: During the pandemic, the route of immunoglobulin treatment should be individualized based on each patient's characteristics and expectations. Telehealth services have emerged as a crucial tool for monitoring patients with chronic disorders, facilitating effective communication and personalized care.