The atherogenic index of plasma (AIP) is a recent biomarker linked to atherosclerosis that has been validated as a novel indicator for myocardial infarction (MI). However, the relationship between AIP and the severity of coronary artery disease (CAD) in MI patients is still ambiguous, particularly among individuals with different glucose metabolic conditions. A total of 741 participants who were immediately assessed with coronary angiography upon admission and diagnosed with acute MI were recruited. The severity of CAD was assessed based on the number of narrowed vessels. AIP tertiles were used to divide the patients into three groups (T1: AIP <
0.030
T2: 0.030 ≤ AIP ≤ 0.316
T3: AIP >
0.316). The American Diabetes Association's guidelines define three types of glucose metabolic state: diabetes mellitus (DM), prediabetes (Pre-DM), and normal glucose regulation (NGR). Logistic regression analysis was utilized to confirm an association between AIP and CAD severity in MI patients. ROC curves were employed to evaluate the diagnostic utility of AIP for CAD severity in MI patients. In MI patients, a statistically significant correlation was found between AIP and the severity of CAD, with logistic regression analysis revealing a strong association (OR: 2.055
95% CI: 1.189-3.550
P = 0.009). Following adjustments for risk factors in the logistic regression model, AIP remained an independent predictor of multi-vessel CAD (OR: 2.902
95% CI: 1.555-5.521
P <
0.001). Moreover, compared with the T1 group, the odds ratios for multi-vessel CAD in the T2 and T3 groups were 2.039 (95% CI: 1.321-3.175
P = 0.001) and 2.087 (95% CI: 1.317-3.340
P = 0.001), respectively. The area under the curve for predicting CAD severity with AIP was 0.568 (95% CI: 0.520-0.616
p = 0.006). In addition, a significant association was observed between AIP and an increased risk of multi-vessel CAD in the Pre-DM group. In MI patients, AIP is closely associated with the risk of multi-vessel CAD and the prediction of the severity of CAD. In Pre-DM patients, AIP is clearly associated with the severity of CAD, whereas this association is absent in the NGR and DM groups.