A total of 57 articles were identified through the database and manual searching. Duplicate articles were removed (n = 40) and 17 studies were assessed at the title and abstract level. Two independent reviewers conducted the screening process. Thirteen articles were retained for full-text screening; seven were retained for quality appraisal and were included in the synthesis. Appendix 3 illustrates the stages of the study selection process.

The methodological quality assessment of the 7 included studies was conducted by two independent reviewers (Appendix 4). All included studies stated the research methodology and the research question or objectives and used appropriate data collection approaches and data analysis. Four studies [20,21,22,23] indicated the researcher’s influence on the research and vice-versa. Except for one study [24], ethical approval was reported for all included studies.

Seven studies were included in the review. These studies were conducted either in a hospital or community setting [20,21,22,23,24,25,26]. Three studies were conducted in Australia [21,22,23], and one study each in Ghana [24], the USA [26], the UK [20], and India [25]. The sample size of studies ranged from 17 [25] to 39 [22]. Appendix 5 presents an overview of the study characteristics.

Twenty-eight findings were extracted and synthesized into four themes: received support, lack of knowledge, medication issues, and the importance of routine.

Findings from four studies [21, 22, 24, 26] contributed to this category. Family and healthcare providers were perceived as important sources of support in encouraging medication adherence. The family provided emotional support: “I don’t think I’d be alive truly if it weren’t for my husband… the wonderful part about that is it’s great to have that support when you don’t feel good” (26, p.22–23). Participants believed that having to take multiple medications can be overwhelming and family members played an important role in supporting medication adherence: “As you know they (my medicines) are laid out for me—left to my own devices, I don’t know how confident I’d be. I fob it off—my wife puts them out” (21, p.8). Support from healthcare providers clear communication and understanding of the importance of adhering to medication were described: “I think a doctor who is upfront and honest and open with you and creates an atmosphere that you feel very comfortable bringing up anything—personal problems at home, wherever—because all that affects the medication. I remember asking Dr. at that time here, ‘Do I need all this medication? Why do I need all this medication? Why do I need all this?’ And he said, ‘To live.’ You need all this medication to live” (26, p.23).

Participants expressed satisfaction with providers in relation to adequate explanations about the medication: “She (endocrinologist) has a fair idea of my history, they know you. It’s a lot easier, you tend to talk to them more easily. ‘‘Hang on, Charlie, you’ve got these seven or eight [tablets]. You don’t need to be on that one” (22, p.1748). However, one study [24] reported that a lack of support influenced the participants’ decision to discontinue medication. The environment and culture within the family could discourage people from taking their medication: “Where I come from, people don’t believe in scientific medications at all. So, when I returned from the hospital with the drugs, family members encouraged me to abandon them. As I started taking the drugs, my husband was not happy with that. He said, it is against the norm to take drugs. I initially took it for a joke but as he persisted I had to stop”[24].

Two studies discussed the impact of routine on medication adherence [21, 23]. Having a routine was described as helpful in supporting people to remember to take their medications. Routine created a behavioral habit that could strengthen adherence. One participant commented: “When you get into a habit, you’re less likely to forget taking one” (23, p. 2113). Establishing a routinely reinforced self-discipline, which encourages repetition of the behavior or habit: “breakfast automatic—pills and blood pressure—67 years on insulin” (21, p.7). However, findings from one study [21] described how routine could negatively influence medication adherence behavior. Some participants who were on medication for a long time claimed that they deliberately did not take their prescribed medications because they became uninterested and wanted to have a break from taking medications: “I’ve been taking medicines for so long I get a bit bored with it… that’s just the way I am—for a week or so I may not take them for a day. Occasionally I don’t take my medicines—9/10ths of the time I do—I like a bit of a break from them” (21, p. 8).

Two studies [21, 22] identified that lack of knowledge could be a significant contributor to medication non-adherence; not knowing about the purpose of taking medications could discourage people from adhering to their medications. Participants stated that knowing more about the importance of good disease control earlier before developing complications could provide them with a clear expectation of disease processes: “I wasn’t aware (of the dangers) blood pressure earlier and if I was, it would have been different” (21, p.5). Not having knowledge and information about medication could inadvertently discourage people from taking medication: “I can’t read what’s on the packet, I just pick which ones I like but I couldn’t tell you which one’s doing what job”(22, p.1751).

Three studies identified issues that discouraged people from adhering to medication [20, 22, 24]. Firstly, concerns about medication side effects were perceived as an issue that discouraged people from adhering to their medications. Experiencing unpleasant side effects impacted adherence with medication plans: “What I was going through while taking the medication was unpleasant. I was feeling uncomfortable and not as normal as I used to be. Because of that I advised myself and stopped taking the medication” (24, p.9). Concerning about side effects discouraged people from taking their medications: “I decided to read about the side effects before taking the drugs and what I read scarred me. I did not make any attempt to the take medicines because I didn’t want to go through the side effects,” (24, p.9). The prioritization by condition was influential. Giving priority to medications that treated conditions seen as the most important, hence, they did not adhere to all prescribed medication appropriately: “If I stop taking medicine for diabetes, I’m not likely to go blind or lose my feet tomorrow, and I might get hit by a truck in the next 20 years. If I stop taking the medication to control my blood pressure I might have a stroke tomorrow and I don’t want to do that” (20, p.1208). Polypharmacy was a recurring issue highlighted in one study [22]: “It was not pleasant definitely, when I was taking one in the morning, one in the afternoon, one in the evening and so on, it was confusing. Did I take this? Did I take it in the morning?” (22, p.1751).