Purpose: To assess macular thinning in individuals with prediabetes or type 2 diabetes without diabetic retinopathy (DM2 w/o DR) compared with individuals with normal glucose metabolism (NGM). Methods: Using spectral domain optical coherence tomography (SD-OCT), we measured macular thickness in six subfields as defined by the Early Treatment Diabetic Retinopathy Study (ETDRS) in 1838 participants from The Maastricht Study, a population-based cohort study (mean age 59 ± 8 years, 49% men, 1087 NGM, 279 prediabetes, 472 DM2 w/o DR). Multivariable linear regression was used to assess the association between macular thickness and glucose metabolism status. Results: After adjustment for age, sex and spherical equivalent, individuals with prediabetes showed a significant decrease in pericentral superior macular thickness [β = −2.14 μm (95% confidence interval (CI): −4.24 to −0.03), p < 0.05] compared with individuals with NGM. In individuals with DM2 w/o DR, the fovea [β = −4.05 μm (95% CI: −6.30 to −1.79), p < 0.001] and the four pericentral quadrants (range: β = −4.64 to −5.29 μm, p < 0.001) were significantly thinner compared with individuals with NGM. There was a significant linear trend of macular thinning with severity of glucose metabolism status in five subfields (p < 0.001). Conclusion: Macular thickness is reduced in prediabetes and a greater reduction occurs in DM2, even before DR is clinically present. About half of the thinning observed in DM2 w/o DR was already found in prediabetes. Generalized thinning of the macula could be related to thinning of the temporal side of the optic nerve head through the connecting papillo-macular bundle.