Health Literacy and Medication Adherence in Polypharmacy: A Systematic Review for Clinical Practice.

Health literacy (HL) is a critical but often overlooked factor in medication adherence, particularly for polypharmacy patients. Despite 387 studies on adherence published since 2019, only 12% examined HL as a primary variable. To synthesize evidence on the impact of HL levels on medication use and adherence. We conducted a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guided review of 16 studies (2019-2024) from PubMed, Scopus, and SciELO, focusing on HL tools and adherence measures. Low HL (LHL) had a 2.6 times higher rate of unintentional non-adherence and 68% more misinterpretations of prescriptions (p < 0.01). Pharmacist-led interventions and the use of visual schemes increased adherence and reduced dosage errors by up to 52%. Patients with LHL showed 35% more hospital readmissions within 30 days. HL screening should be integrated into polypharmacy management protocols. Policy-makers must prioritize HL-sensitive interventions to reduce avoidable costs.