This study investigated the effect of streptozotocin (STZ)-induced type 1 diabetes mellitus (DM) on total protein concentration and levels of sodium (Na+), potassium (K+), magnesium (Mg2+), zinc (Zn2+), copper (Cu2+), calcium (Ca2+), and iron (Fe2+) in the pancreas, parotid, submandibular, and lacrimal glands of the rat, compared to age-matched control animals. Protein concentrations were measured by the Bradford Assay, whereas levels of Na+, K+, Mg2+, Zn2+, Cu2+, Ca2+, and Fe2+ were measured by flame photometry and atomic absorbance spectrophotometry. The results show marked changes in the characteristics of diabetic and control animals. Diabetic rats and their different glands weighed significantly (P < 0.05) less compared to age-matched controls. Diabetic rats also have significantly elevated blood glucose and significantly reduced plasma insulin, compared to controls. The results also show that the concentrations of proteins and levels of cations were significantly (P < 0.05) reduced in the pancreas, parotid, submandibular and lacrimal glands of diabetic rats, compared to glands from age-matched animals. These differences in the cation contents and protein levels in STZ-induced DM in this study, along with supporting evidences from previous studies, may provide evidence for the development of long-term complications of DM including exocrine gland deficiencies.