A team from Hull York Medical School studied 15 patients with type-2 diabetes and chronic kidney disease (CKD).
It showed that erythropoietin-stimulating agents or IV iron can lead to falls in HbA1c, without a change in glycaemic control.
'It is essential that healthcare professionals are aware of the potential fluctuations of HbA1c that can occur in this patient group,' the team said.
Capillary glucose measurement and concurrent use of continuous glucose monitoring are the best alternative means of measuring glycaemic control, it added.
'Alternative methods for measuring glycaemic control such as capillary glucose testing and continuous glucose monitoring should be employed and therapy should not be based on the HbA1c value alone.
'This has particular significance when considering national, international or health service glycaemic targets, such as the QOF in the UK which almost exclusively use HbA1c as the sole index by which treatment success is judged,' it said.
The researchers point out that erythropoietin-stimulating agents and IV iron are commonly used therapies in the management of anemia in patients with CKD.
In addition, patients with both diabetes mellitus and CKD have a higher prevalence of severe anemia as compared with patients with CKD alone, they said.