Background <p>Early and accurate diagnosis of diabetes is essential to prevent long-term complications. While the oral glucose tolerance test (OGTT) is the reference standard, it is often impractical. Glycated hemoglobin (HbA1c) is widely used instead, but it can be unreliable in conditions that alter erythrocyte lifespan. Glycated albumin (GA) and fructosamine (FA) represent promising, short-term glycemic biomarkers that are independent of red blood cell turnover; however, their exact diagnostic accuracy remains uncertain.</p> Methods <p>This systematic review and meta-analysis protocol follows PRISMA-DTA guidelines. We will search MEDLINE (via PubMed), Scopus, and Web of Science from inception to December 2025 for observational studies evaluating GA or FA against OGTT in adult populations. Two independent reviewers will screen studies, extract data, and assess methodological quality using the QUADAS-2 tool. Diagnostic accuracy measures will be pooled using a bivariate random-effects model, and hierarchical summary receiver operating characteristic (HSROC) curves will be constructed.</p> Discussion <p>This review will provide comprehensive evidence on the diagnostic performance of GA and FA, clarifying their potential utility as alternatives to HbA1c. Findings will help inform clinical practice, laboratory decision-making, and future guideline development, particularly for populations where HbA1c testing is unreliable.</p> Systematic review registration <p>PROSPERO CRD420251236959</p>