The World Health Organization (WHO) reported a nearly double increase in the prevalence of DM among adults older than 18 years from 4.7% in 1980 to 8.5% in 2014 and stated that as a part of the 2030 agenda for sustainable development, early mortality due to DM should decrease to one-third (
1). On the other hand, e-health technologies including mobile phone are increasingly being used (
28) and it is estimated that the global smartphone market will grow to reach 3.45 billion mobile app users by 2017. Theoretically, e-health can play its role in the management of DM through different ways including counseling, decision-aids making, appointment scheduling, educating and training for remote behavioral changes, follow-ups, using glucometer apps, reporting glycemic indices such as HbA1c, sending feedback to physicians, receiving feedback from physicians, dietary guidance, medication adherence, and sending reminders for continuity of care (
5). Data show that the most number of mobile apps for medical use were made for DM and most studies that aimed to assess the clinical efficacy of m-health focused on this disease or its associated risk factors (
6). In this study, we found that the effects of m-health and other types of e-health tools on different aspects of DM including prevention, diagnosis, and especially treatment were assessed by a large number of studies in many countries, especially in North America and Europe countries. Most of the research included a variety of interventions and a diversity of measured outcomes. Nearly half of the SR/MA studies proved the positive effects of these interventions on the outcome of DM contrary to another half that declared unclear, inconsistent, or non-conclusive results. The findings showed that studies in the first group were more powerful in terms of the type of included studies, had nearly three times higher total sample size, higher quality scores, and less overlap among their subset studies. However, the total study population in the total of 550 subset studies in 17 SR/MA studies included in the current analysis was not high enough in proportion to the number of available e-health tools, the variety of countries, and DM patients’ population. These figures reveal that decision-making based on available evidence is not easy and what confirms our claim in this regard is that at least 53% of the surveyed studies recommended conducting further research with stronger methods. Evidence shows that 99% of received mobile text messages are opened, 90% of all mobile text messages are read within three minutes of being received (
4), and reminders have the highest impact on changing patients behaviors while they are most easily implemented compared to personalized messages, education, dashboards, gamification, and other m-health facilities (
6). Similarly, the findings of our study showed that text messaging by mobile phones, especially when integrated with other tools, was the most common applied e-health intervention for improving the outcome of DM. This result came from a one high-quality MA study that was conducted in six countries (
12) and another SR study with moderate quality that was conducted in nine countries (
18). One study with moderate quality that studied only DM1 patients in five countries revealed that text messaging was feasible and enjoyable but its long-term effect on the glycemic index of these patients was unclear (
21). The importance of long-term use and sustainability in using such tools to cause an improvement in the DM outcome were noted by only 25% of the studies (
15,
16,
21,
22). The assessment and importance of considering the e-health effect on QOL and satisfaction of diabetic patients were regarded by 25% of the studies (
14,
17,
18,
26) and except one study (
25), none of them recommended considering patients’ views in designing such tools. The evidence shows that patients’ views, values, expectations, and feedbacks, as the main part of these processes, are actually neglected and this may be another important reason for the failure of these tools to achieve expected success following using these technologies. Another report showed that these apps have not yet had an enough significant acceptance rate by target groups and most apps are too narrow in their functionality or too technical to become a daily companion (
29). Moreover, the evidence of our study revealed that the importance of considering medical professionals’ views and their experiences in designing and developing e-health tools was not regarded by any of the included studies. However, companies claimed that in 2015, in 51% of instances of m-health apps development, medical professionals were a member of their team and in 45%, they collaborated with developers of these tools (
6). On the other hand, they announced that their hope for these tools to be used by medical care providers has decreased (
6). Therefore, this paradox should be evaluated by non-biased research that also considers the economic impact of using these tools on the income and time of medical physicians. The evidence of companies shows that medical doctors are the most threatened group by m-health industry due to decreasing their visiting income when patients receive remote care through using these apps. Therefore, they are not welcome to use these methods (
6). The educational effect of m-health on reducing HbA1c was remarked by two studies (
12,
18). However, two other studies did not show a clear result and recommended doing further research on it (
24,
27). Designing e-health tools based on behavior change techniques (BCTs) was emphasized by only one study (
13) but it was unknown how much behavioral experts’ opinions are included in the planning of these facilities. It should be considered that BCTs are diverse, dynamic, and increasing. BCTs for remote changing of DM patients’ behaviors may differ according to the characteristics of patients in different places and in different times. It means that a kind of BCT may be successful in one group of patients or in a specific time but it may not work in another group of patients or another time. Therefore, there is no a single prescription for the behavioral changing of all DM patients in different places or in different times and participation of BCTs experts in the planning of such tools is necessary. Cost-effectiveness of e-health tools is another important aspect that should not be ignored (
5). However, 18% of the included studies reported cost-effectiveness and 35% concluded unclear results or lacked enough evidence on it. Therefore, determining standard indices for cost-effectiveness is a key step for measuring this item by researchers aiming to have a holistic assessment of e-health effect on the DM management. A nearly holistic approach in conducting research about the e-health effect on the management of DM was applied by only two studies (
14,
18). The characteristics of used e-health apps such as format, frequency, and timing and full testing of them were only recommended by one study (
21) while most studies did not consider these points. By the above evidence, we can better understand that the management of DM by e-health is complex. The characteristics of the types of DM are varied and patients with DM in different parts of the world or during their lives show different responses to interventions. Moreover, there is an increasing trend in the production of tools and apps for the management of DM. Furthermore, health care providers’ approach and their reaction to these technologies add to the complexity of this issue. Therefore, the outcome of using these tools is based on the characteristics of all these four aspects: DM, patients, care providers, and tools themselves. In each of these aspects, many sub-items should be regarded both in designing interventions and in conducting research with the aim of assessing or evaluating their efficacy in the management of DM. For example, the type of DM, DM1, DM2, and Gestational DM, the duration of DM, the level of the glycemic index, and the severity of DM potentially can influence the outcome of DM. Patients’ characteristics including demographic, psychological, social, and economic status and their views, values, and perspectives may determine the consequence of such interventions, as well. Health care providers’ opinion and behaviors are also important in using these tools for the establishment of a synchronous or asynchronous two-way communication with users. The effect of these interventions on the income of physicians or their time may also be an important determinant of their behaviors in this regard. Tools’ features including to what extent they are set by standard criteria, are adopted by users, meet behavioral change models, and are secure, accessible, applicable, user-friendly, and costly can determine the outcome in DM patients who use these tools. Therefore, there is no doubt that no single policy or intervention can ensure or satisfy us to have significant positive effects on the improvement of all aspects of DM or have a persistent effect on it. Therefore, research, regardless that in which part of the world it is conducted, should apply a strong method to provide a less controversial evidence for decision making by designers, publishers, patients, and healthcare providers. However, the primary priority is setting standard assessment tools that consider all of the above items before conducting such studies. We recommend also establishing a surveillance system based on all mentioned items and by the participation of all stockholders to assess the efficacy of e tools in the management of chronic diseases such as DM. There are two other important points that should be regarded. The first is that in addition to the e-health tools and research that is related to the therapeutic outcomes in diabetic patients, there is also a need to design or assess the interventions that are used for the prevention of DM. The second point, as also emphasized by WHO, is that these tools cannot and should not be regarded as a replacement for higher valued decision-making, supervision on treatment, and applied care by specialists; these tools are potentially facilitators and have a contributory role in the management of DM. Our study had some limitations. We did not investigate gray literature and non-English papers and we did not conduct a secondary MA due to the overlap among six included MA studies. However, this study has some unique strengths; we included all negative results, as well as positive results, to avoid publication bias. Moreover, calculating the overlap of references among the included studies, although it was hard and time-consuming, was done precisely and presented as figures. In this study, we also categorized the included studies into two distinct groups as supportive and non-supportive studies about the effect of e-health on the management of the glycemic index of DM and then by providing their important characteristics in the last paragraph of the result section, which enables readers to compare them at a glance.