Diabetes and Its Effect on Hemoglobin and Red Blood Cell Count
Yes, diabetes can lead to increased hemoglobin (Hb) and red blood cell (RBC) count, particularly in patients with poor glycemic control. This relationship is supported by clinical evidence and has important implications for patient care.
Mechanism and Evidence
Hyperglycemia in diabetes can increase red blood cell count, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) 1.
Research has demonstrated a positive correlation between glycosylated hemoglobin (HbA1c) levels and total red blood cell count in diabetic patients, suggesting that poorer glycemic control is associated with relative polycythemia 2.
The proposed mechanism involves the higher proportion of glycosylated hemoglobin (HbA1) in poorly controlled diabetics, which has a higher oxygen affinity that may induce sufficient tissue hypoxia to cause relative polycythemia 2.
Clinical Implications
When interpreting HbA1c results in diabetic patients, clinicians should be aware that the relationship between HbA1c and mean glycemia exists because erythrocytes are continuously glycated during their 120-day lifespan, with the rate of glycohemoglobin formation proportional to ambient glucose concentration 3.
In the Diabetes Control and Complications Trial, an HbA1c of 6% corresponded to a mean plasma glucose level of 135 mg/dL, with each 1% increase in HbA1c corresponding to an increase in mean plasma glucose of approximately 35 mg/dL 3.
Insulin appears to have a direct effect on erythrocyte deformability, which is decreased in diabetic patients and shows negative correlation with glycosylated hemoglobin and actual blood glucose levels 4.
Confounding Factors and Considerations
When assessing HbA1c in diabetic patients, it's important to consider potential confounding conditions that may affect results 3:
- Hemoglobin variants can interfere with HbA1c measurements
- Conditions with increased red cell turnover (pregnancy, blood loss, transfusion, erythropoietin therapy, hemolysis) may lead to falsely decreased HbA1c values
In patients with chronic kidney disease (CKD) and diabetes, factors that may contribute to falsely decreased HbA1c values include reduced red blood cell lifespan, transfusions, and hemolysis, while falsely increased values may occur due to carbamylation of hemoglobin and acidosis 3.
Iron deficiency anemia is reported to falsely increase HbA1c results, while vitamins C and E may falsely lower HbA1c results by inhibiting glycation of hemoglobin 3.
Clinical Recommendations
For accurate assessment of glycemic control in diabetic patients, HbA1c remains the best clinical marker, particularly when combined with self-monitoring of blood glucose 3.
In conditions where HbA1c may be unreliable (such as hemoglobinopathies or altered red cell turnover), only blood glucose criteria should be used for diagnosis and monitoring of diabetes 3.
For patients with diabetes and chronic kidney disease (CKD), HbA1c can still be used to monitor glycemic control for patients with eGFR down to 30 ml/min per 1.73 m², but its accuracy may be compromised in more advanced kidney disease 3.
Continuous glucose monitoring (CGM) may be particularly useful in patients where HbA1c values are not concordant with directly measured blood glucose levels or clinical symptoms 3.
Understanding the relationship between diabetes, hemoglobin, and red blood cell count is important for accurate interpretation of laboratory values and optimal management of diabetic patients.