Purpose To assess the association of type 2 diabetes mellitus (T2DM) and insulin glargine treatment with bone mineral density (BMD) in Chinese people. Methods This retrospective study included 50 subjects with T2DM: 25 received oral glucose-lowering medication (ORL group), and 25 received oral glucose-lowering medication in combination with insulin glargine injection (CGI group). Thirty non-diabetic control subjects were also included. BMD was measured at lumbar vertebrae 1–4 (L1–L4), spine bone mineral density (sBMD) results summary (L2–L4), femoral neck and trochanter by dual-energy x-ray absorptiometry. Results Compared with non-diabetic controls, people with T2DM had significantly lower mean BMD at L2 (1.073±0.120 vs 0.984±0.158), L3 (1.094±0.129 vs 0.991±0.163) and L4 (1.089±0.130 vs 0.982±0.165) (all P<0.05), significantly lower levels of serum calcium (2.02±0.22 vs 2.27±0.17 mmol/L, P<0.05), PTH (24.19±9.71 vs 31.52±8.96 pg/mL, P<0.05), and higher serum phosphate levels (1.43±0.37 vs 1.20±0.15 mmol/L, P<0.05). The CGI group had higher L2, L3 and L4 BMD and sBMD (L2–L4) (P<0.05), higher serum calcium levels (2.19±0.11 vs 1.98±0.20 mmol/L, P<0.05) and lower serum phosphate levels (1.28±0.20 vs 1.58±0.43 mmol/L, P<0.05) versus the ORL group. BMD and serum calcium levels were associated with the application of insulin glargine. Conclusion These results suggest that insulin glargine may affect bone metabolism in patients diagnosed with T2DM. The study has implications for the selection of hypoglycemic agents for diabetic patients at risk of osteoporosis.