Posttraumatic stress disorder (PTSD) is one of the most common psychiatric disorders. However, we should not neglect the somatic aspects of PTSD. Associations with cardiovascular diseases (CVD) are particularly concerning because PTSD was associated with an even 53% higher risk for CVD. This study aimed to analyze the prevalence of several CVD risk factors, especially diabetes mellitus among PTSD patients divided into three groups according to obstructive sleep apnea (OSA) risk stratification (low, intermediate, and high). This cross-sectional study included one hundred male PTSD veterans. The mean age was 53 (40–67) years. The estimated OSA risk was 95% for the whole cohort, and 53% were in the high-risk group. Median HbA1c was 5.6 (4.6–10)%. The hemoglobin A1c (HbA1c) levels showed that 34 patients were in the prediabetes group, and 20 of them fulfilled the criteria for diabetes. However, only 13 of them were aware of their previous diagnosis of diabetes mellitus. In testing knowledge about diabetes, 62% and only 23% of patients knew the correct definition of HbA1c and level of fasting plasma glucose, respectively. Diabetic patients had insufficient knowledge about diabetic complications and treatment. A higher level of PTSD symptoms in veterans was associated with a higher prevalence of OSA. The results strongly support further research and education into early detection of CVD risk factors associated with PTSD.