Objective: The aim of the study was to assess the effect of long-term prednisolone on fasting and post-glucose load glucose concentration in patients with inflammatory rheumatological disease. We hypothesized that prednisolone would predominantly increase post-glucose load glucose concentration and that fasting glucose would have poor sensitivity as a screening test for diabetes in patients receiving chronic prednisolone therapy. Methods: In a cross-sectional study of subjects with inflammatory rheumatological disease but without known diabetes, 60 subjects [age = 70 (±10) years, 62% female] who were receiving chronic (>6 months) prednisolone [6.5 (±2.1) mg/day] (Group 1) and 58 controls [age = 70 (±11) years, 62% female] who had not received oral glucocorticoids for at least 6 months (Group 2) underwent an oral glucose tolerance test.Results. Fasting glucose was significantly lower [5.0 (±0.1) vs 5.3 (±0.1) mmol/l, P = 0.02) and post-glucose load glucose concentration significantly higher [8.0 (±0.4) vs 6.8 (±0.3) mmol/l, P = 0.02] in Group 1 than in Group 2. In a multiple regression analysis, glucocorticoid use (P = 0.004) and log CRP (P = 0.02) were independently associated with fasting glucose, while waist circumference (P = 0.01), but not glucocorticoid use, was independently associated with post-glucose load glucose concentration. A fasting glucose ≥5.6 mmol/l had 33 and 83% sensitivity for diabetes in Groups 1 and 2, respectively. Conclusion: There is discordance between a reduced fasting and increased post-glucose load glucose concentration in rheumatological patients on long-term prednisolone. Therefore fasting glucose has poor sensitivity to screen for diabetes in prednisolone-treated patients. Treatment of prednisolone-induced hyperglycaemia should be directed at the postprandial period.