Provided herein are nitrite salts of 1,1-dimethylbiguanide; and isotopic variants thereof; and pharmaceutically acceptable hydrates and solvates thereof. Also provided herein are their pharmaceutical compositions and methods of use for treating, preventing, or ameliorating one or more symptoms of diseases associated with and/or caused by an abnormal blood glucose level. Further provided herein are methods of their use for treating, preventing, or ameliorating one or more symptoms of a cardiovascular disease.