Hereditary hemorrhagic telangiectasia (HHT; Rendu-Osler-Weber syndrome) affects the capillary and larger vessels, leading to arteriovenous shunts. Epistaxis is the main symptom impairing quality of life. The aim of the Osler Calendar is to offer information about the extent of the systemic disease and the current state of treatment. A care plan with information on the rare disease and self-treatment of epistaxis was created. Organ examinations and ongoing treatments were recorded. A questionnaire documents the treatment success, including patient satisfaction, frequency of hemorrhage and hemoglobin levels. The patients using the Osler Calendar for at least one year (n = 54) were surveyed. Eighty-five percent of patients (n = 46) used the calendar to gain information about HHT. Seventy-two percent (n = 39) used the Osler Calendar for instructions on the self-treatment of nosebleeds. The calendar increased patients' understanding for the need for organ screenings from 48% (n = 26) to 81% (n = 44). Seventy-nine percent (n = 43) of patients confirmed that the Osler Calendar documented their therapeutic process either well or very well. Fifty-two percent (n = 28) saw an improvement in the therapeutic process due to the documentation. The Osler Calendar records the individual intensity of the disease and facilitates the communication between attending physicians. It is a tool for specialists to review treatment strategies. Furthermore, the calendar enhances patients' comprehension of their condition.