The present work is a cross-sectional study aimed to evaluate the serum levels of calcium and Glycated Hemoglobin (HbA1c) of (40) patients with type 2 diabetes mellitus, attending Center clinic in Khartoum North-Sudan, and (40) apparently healthy (non-diabetic) volunteers as control group. Age and sex of the test group were matched with the control group. Serum levels of calcium were measured by auto analyzer Bs-200 (instruments and reagents from Mindray Company) and HbA1c amount was measured by CERA-STAT TM 4000 Analyzer (reagents and instruments from Ceragem Medisys Company). Data was analyzed using SPSS. The results showed a significant reduction in the mean of serum calcium level of the diabetic group when compared with the control group (p value <0.05), whereas HbA1c was increased in diabetic patients (type 2) compared to the control group (p. value <0.05). However there was a good negative correlation between the serum calcium levels and HbA1c in diabetic patients. The results revealed that the increase in HbA1c, in diabetics of type 2 diabetes mellitus, is accompanied by a significant decrease in calcium serum levels, so uncontrolled diabetic patients are at risk of hypocalcaemia compared to controlled patients. This effect was not influenced by gender or duration of diabetes in the studied group.