To make sure I get it correct I'm going to cut and paste this with a bit of bolding. It is recently dated Jan 2014 and is from the authority responsible for world wide standardisation of HbA1cs
http://www.ngsp.org/factors.asp
Any condition that shortens erythrocyte survival or decreases mean erythrocyte age (e.g., recovery from acute blood loss, hemolytic anemia) will falsely lower HbA1c test results regardless of the assay method used [2]. HbA1c results from patients with HbSS, HbCC, and HbSC must be interpreted with caution given the pathological processes, including anemia, increased red cell turnover, and transfusion requirements, that adversely impact HbA1c as a marker of long-term glycemic control. Alternative forms of testing such as glycated serum protein or glycated albumin should be considered for these patients.
Iron deficiency anemia, a major public health problem in developing countries, is associated with higher HbA1c and higher fructosamine [3].
Consistent with these observations, iron replacement therapy lowers both HbA1c and fructosamine concentrations in diabetic and non-diabetic individuals [3-5]. HbA1c , but not glycated albumin, is increased in late pregnancy in nondiabetic individuals owing to iron deficiency [6]. Insight into the mechanism was recently obtained by the observation that malondialdehyde, which is increased in patients with iron deficiency anemia [3], enhances the glycation of hemoglobin [7].
Alternative measures of glycemic assessment (e.g., glucose monitoring) must be used in the presence of significant iron deficiency anemia, at least until the iron deficiency has been successfully treated.