Aims/introduction: In previous studies H2 administration has clearly shown effectiveness in inhibiting diabetes. Here, we evaluated whether subcutaneous injection of H2 shows enhanced efficacy against type 2 diabetes mellitus (T2DM) induced in mice by a high-fat diet and low dose streptozotocin (STZ) treatment. Material and methods: H2 was injected subcutaneously at a dose of 1ml/mouse/week for four weeks. T2DM associated parameters were then evaluated to determine the effectiveness of subcutaneous H2 administration. Results: The body weight of H2 -treated mice did not change over the course of the experiment. Compared to the untreated control animals, glucose, insulin, low-density lipoprotein (LDL) and triglyceride (TG) levels in serum were significantly lower in treated mice, while high-density lipoprotein cholesterol (HDL) in the serum was significantly higher. Glucose tolerance and insulin sensitivity were both improved in H2 -treated mice. Diabetic nephropathy (DN) analysis showed significant reductions in urine volume, urinary total protein and β2 microglobulin, kidney/body weight ratio and kidney fibrosis associated with subcutaneous injection of H2 . Conclusions: Subcutaneous injection of H2 significantly improves T2DM and DN related outcomes in a mouse model, supporting further consideration of subcutaneous injection as a novel and effective route of clinical H2 administration. This article is protected by copyright. All rights reserved.