Paradoxes in Modern Diabetes Care: Time, Context, Complexity, and the Limits of Biomarker-Based Reasoning

Observations described as paradoxical are common in diabetes: intensive glucose lowering may fail to improve macrovascular outcomes; long-term benefit may persist after HbA1c convergence; SGLT2 inhibitors can cause an early eGFR dip despite kidney protection; ketoacidosis may occur without marked hyperglycaemia; and contrasting GIP receptor strategies can coexist with effective GLP-1-based therapy. We conducted a structured narrative review of PubMed/MEDLINE literature updated to 8 September 2026, prioritising randomised trials, meta-analyses, consensus statements, and human mechanistic evidence. We propose a two-level framework for interpreting these observations. At the biological level, apparent contradictions arise from time, clinical context, and system complexity. At the measurement and inference level, dynamic and heterogeneous biology may be compressed into snapshots, thresholds, aggregate estimates, or simplified representations of biological state. The framework is applied to intensive glycaemic control and metabolic memory, early retinopathy worsening and treatment-induced neuropathy, SGLT2-associated eGFR change and euglycaemic ketoacidosis, multi-receptor pharmacology, HbA1c in advanced kidney disease, the obesity paradox, and statin-associated dysglycaemia. These phenomena do not share a single biological mechanism. Rather, they illustrate how interpretation can become misleading when relevant temporal, contextual, systems-level, or representational information is omitted, or when biomarkers, mechanisms, surrogates, prediction, and patient-relevant outcomes are treated as interchangeable evidential roles.