Objective: In patients of diabetes mellitus (DM), heart rate variability (HRV), an index of autonomic nervous system activity, tends to be lower than in healthy individuals. This reduction in HRV is associated with an increased risk of cardiovascular diseases. We aimed to evaluate HRV under varying conditions with novel indicators in patients with DM. Methods: The patients were recruited from patients with type 2 DM (T2DM) aged 20 to 79 years old from two facilities from January 2020 to December 2023. The control comprised patients without DM. Patients taking oral corticosteroids, adrenergic agonists and antagonists, and those with malignant tumors were excluded. Heart rate (HR) was measured under varying conditions of rest, standing and deep breathing (inhalation and exhalation alternating every 5 seconds). The R-R interval variation was continuously recorded in each segment of 33 beats. Subsequently, the peak HRs for each load were obtained: minimum HR during rest (mHr), maximum HR during standing (MHs), and minimum HR during deep breathing (mHb). Additionally, the SD-RR for each load was calculated. Results: We analyzed a total of 117 subjects, including 75 with T2DM and 42 without DM. The participant demographics were as follows: mean age of 55.4±13.9 years, BMI of 25.9±5.6, eGFR of 71.5±26.1 mL/min/1.73m 2 , HbA1c of 7.31±2.26 %, with 46 % of male, and duration of T2DM in patient group at 8.2±8.3 years. The subjects were categorized into three groups: G1 - non DM with CV-RR≧2, G2 - T2DM with CV-RR≧2, and G3 - T2DM with CV-RR<2.mHr was G1: 64.5±7.4, G2: 69.4±7.7, G3: 75.2±13.1 (beats/minute, p<0.001). G3 is markedly higher than G1 and G2. Furthermore, the HR change ratio from mHr to MHs was: G1: 1.36±0.12, G2: 1.31±0.11, G3: 1.22±0.10 (p<0.001). G3 is markedly lower than G1 and G2. The HR change ratio from mHr to mHb was: G1: 0.99±0.04, G2: 0.96±0.05, G3: 0.96±0.05 (p=0.043), with G3 being markedly lower than G1. The SD-RR during rest was: G1: 26.4±18.6, G2: 28.0±12.5, G3: 10.1±4.4 (p<0.001), with G3 being markedly lower than G1 and G2. Conclusion: Assessing R-R intervals under varying conditions of rest, standing, and deep breathing can indicate autonomic nervous system dysfunction among patients with T2DM.