Erythrocyte and fasting plasma magnesium were assayed by a dyebinding colorimetric method using the metallochromic dye, Calmagite, in 51 diabetic Nigerians and 25 controls. Erythrocyte magnesium concentrations were similar in the diabetics and the controls. Fasting plasma magnesium concentrations were significantly lower only in insulin-treated diabetics as compared to controls. No significant correlations were observed between fasting plasma glucose concentrations and either plasma or erythrocyte magnesium concentrations in the diabetic groups. Also, no significant correlation was found between erythrocyte magnesium and plasma magnesium concentrations. However, erythrocyte magnesium concentrations were directly related to age while plasma magnesium concentrations were directly related to duration of diabetes in all diabetics. Erythrocyte and plasma magnesium concentrations were not significantly affected by sex and degree of plasma glucose control.

These results suggest that insulin-treated black African diabetics may develop hypomagnesaemia which is not associated with depletion of the erythrocyte content of magnesium.