BACKGROUND: Several studies have revealed conflicting results regarding the relationship between serum uric acid (SUA) and blood glucose concentrations. The aim of this study was to identify the shape of the curve between SUA and either fasting plasma glucose (FPG) or HbA1c in diabetic and non-diabetic participants. METHODS: This cross-sectional study of the relationship between SUA and diabetes and non-diabetes was conducted in 10 266 participants. Data from the national baseline survey of the China Health and Retirement Longitudinal Study (CHARLS; 2011-12) were used. Restrictive cubic spline regression and two piecewise linear regression models were used to detect non-linear trends and calculate the slope of each segment. RESULTS: After adjusting for all confounding factors in all subjects, an L-shaped relationship was found between FPG and SUA in males (β  = 3.47, P < 0.01) and females (β  = 5.84, P < 0.01), as well as between HbA1c and SUA in males (β  = 0.10, P = 0.03) and females (β  = 0.12, P = 0.02). In non-diabetic individuals, there was a positive linear correlation between FPG and SUA in females (β = 0.62, P = 0.02). After a diagnosis of diabetes, a negative linear relationship was found between SUA and blood glucose in males, and a nearly L-shaped curve was found in females. CONCLUSIONS: An L-shaped association was found between SUA and blood glucose in both genders. Stratified analysis revealed an L-shaped curve only in diabetic females. Further studies are warranted to investigate the mechanisms of the association between uric acid and blood glucose levels.