Purpose To determine the most effective methods of informing people about the primary prevention of hypertension using a social media website. Materials and methods It was a randomized, prospective, two-stage study conducted on a social media website ( i . e ., the Instagram platform). At Stage 1 Save Your Heart online school was announced, and 945 applicants were registered for the training. The online training programme included the following modules: Risk Factors for Cardiovascular Diseases (CVDs), Heart-Healthy Diet, Cholesterol. What a Patient Needs to Know, Physical Activity for the Prevention of CVDs, Overweight and Obesity, Smoking as a Risk Factor for CVDs, Hypertension: Diagnosis, Hypertension: Treatment, Myocardial Infarction: Diagnosis and Treatment. At Stage 2 a total of 125 participants were randomly selected and assigned into one of the four training groups depending on the training mode, i . e . text posts of up to 4.000 characters, short video clips of up to 5 minutes, text posts followed by video clips or video clips followed by text posts in Group 1 ( n =31), Group 2 ( n =31), Group 3 ( n =33) and Group 4 ( n =30), respectively. Before and after training respondents in all the four groups completed the Heart Disease Knowledge Questionnaire (HDKQ). Results The total number of people who listened to and read the materials of the online school was 2.108 people; the overall engagement (comments, shares and saves) was 1.598 people. The average percentage viewed was 22%. The online school audience was mostly female (84%). A total of 80.8% of participants had post-secondary education. The mean duration of hypertension was 6.1 years. Smokers accounted for 3.2% of the respondents. Before training the number of correct responses for 29 HDKQ statements was 18.4 (CI, 17.5;19.4), with no significant differences between the groups. After training the number of correct responses increased to 21.9 (CI, 21;22.7) ( p (ANOVA) <0.0001). The post-hoc analysis showed that after training the respondents from Group 3 gave the lowest number of correct responses compared to Groups 1 and 2, i . e . Δ=4.9 (CI, -7.8;2.0) and Δ=3.7 (CI, -6.5;-0.8), respectively. Participants from Group 4 had more correct responses than the respondents in Group 3, i . e . Δ=5.2 (CI, 2.2;8.1). The regression analysis showed that the post-training number of correct responses in Group 4 increased on average by 3.9 compared to Group 3 (β=3.94 p =0.04 (CI, 0.21;7.66)). The study showed a significant association between the duration of hypertension and the number of correct responses both before and after training (β=0.20 p =0.007 (CI, 0.06;0.34) and β=0.16 p =0.005 (CI, 0.05;0.27), respectively). No association was found between gender, age, education and the number of correct responses both before and after training. Conclusions In all the 4 groups there was a tendency to increase in the number of correct responses after training, but among the training modes the most effective method of informing people about the primary prevention of hypertension using a social media website corresponded to the following sequence: a video clip of up to 5 minutes followed by a text post of up to 4,000 characters. Participants in Group 3 who received the material in the form of text posts followed by video clips gave the lowest number of correct responses for HDKQ statements after training. The results of this study can be used to design online training programmes for the primary prevention of hypertension.