We examined the association between sarco/endoplasmic reticulum calcium ATPase (SERCA) expression and glycated hemoglobin (HbA_1c) levels since alterations in this protein expression are associated with the genesis of insulin resistance. HbA_1c levels and SERCA protein expression from platelets of Mexican patients diagnosed with type 2 diabetes mellitus (T2DM) were analyzed showing lower values of SERCA expression against the normal values we find in healthy people. Interestingly, as diabetes condition got worse; SERCA protein expression decreased gradually until it was undetectable. The results showed an inverse correlation between HbA_1c and SERCA protein expression in T2DM patients. .