Diabetes mellitus is a long-term metabolic condition characterized by high blood sugar (hyperglycemia) that affects nearly every system in the body. A significant consequence involves the circulating blood components, specifically the red blood cells (RBCs). An elevated red blood cell count, often observed in diabetic patients, signals a potential complication requiring specialized attention. This change in blood composition can significantly increase the risk of serious health issues, particularly those affecting the heart and blood vessels.
Defining Elevated Red Blood Cell Counts
An abnormally high concentration of red blood cells is known medically as polycythemia or erythrocytosis. This condition means the blood contains too many oxygen-carrying cells, which effectively thickens the blood, a state referred to as hyperviscosity. Clinicians measure this concentration using two primary values from a complete blood count: hematocrit (Hct), the percentage of blood volume occupied by red blood cells, and hemoglobin (Hb), the oxygen-carrying protein. Elevated readings for both indicate a higher-than-normal red cell volume.
In diabetic patients, this finding is generally considered a secondary complication, not a primary blood disorder originating in the bone marrow. The elevated count is frequently a physiological response to underlying issues related to chronic high blood sugar. Changes in red cell turnover caused by diabetes can also complicate the interpretation of the Hemoglobin A1c (HbA1c) test, the standard measure of long-term glucose control. If red blood cells have a shortened lifespan, the HbA1c result may appear falsely lower than the patient’s actual average blood sugar level.
Physiological Reasons for Increased RBCs in Diabetes
One primary driver behind an elevated red blood cell count in diabetes is chronic dehydration, which leads to hemoconcentration. When blood glucose levels are poorly controlled, the kidneys excrete excess sugar through increased urination, a process known as osmotic diuresis. This fluid loss reduces the plasma volume, causing the remaining blood components, including red blood cells, to become artificially concentrated, registering as a high hematocrit reading.
Beyond simple fluid loss, the body may genuinely increase red blood cell production in response to tissue hypoxia (oxygen deprivation). Chronic hyperglycemia damages small blood vessels, a microvascular complication that limits oxygen delivery to tissues. Sensing this low oxygen state, the kidneys release more erythropoietin (EPO), a hormone that signals the bone marrow to ramp up red blood cell production.
Several common co-occurring conditions in diabetic patients also contribute to this stimulation. Chronic kidney disease (CKD), a frequent complication of diabetes, can alter fluid balance and oxygen sensing mechanisms. Conditions like obstructive sleep apnea, common in overweight individuals with type 2 diabetes, cause repeated episodes of nocturnal oxygen desaturation. This also triggers EPO release to compensate for the perceived lack of oxygen. The resulting increase in red blood cell volume is the body’s attempt to restore proper oxygen levels, but it compromises blood flow.
Specific Health Risks of High Blood Viscosity
The most significant consequence of an elevated red blood cell count is the resulting increase in whole blood viscosity, making the blood thick and sluggish. This thicker blood flows less efficiently through the already compromised microcirculation of a diabetic patient. Resistance to flow is particularly noticeable in small blood vessels, leading to impaired delivery of oxygen and nutrients to vital organs and tissues.
The high viscosity substantially raises the risk of thrombotic events (dangerous blood clots). Sluggish blood flow allows components like red blood cells and platelets to aggregate more easily, increasing the likelihood of clot formation. This hyperviscosity is associated with an increased risk for deep vein thrombosis (DVT), a clot that typically forms in the legs.
In the cardiovascular system, this increased viscosity places a strain on the heart, which must pump harder to circulate the thicker blood, potentially leading to hypertension or heart failure. The risk of severe arterial events, such as ischemic stroke or myocardial infarction (heart attack), is also significantly elevated because the thickened blood can more easily precipitate clot formation in narrowed blood vessels. Managing this viscosity is a direct strategy for mitigating major cardiovascular complications in people with diabetes.
Treatment and Management Strategies
The primary focus of managing an elevated red blood cell count in a diabetic patient must be strict control of blood sugar levels. Achieving good glycemic control is paramount, as it directly addresses the root cause of osmotic diuresis and hemoconcentration. Effective glucose management reduces the kidney’s need to excrete excess sugar, preventing fluid loss and normalizing plasma volume.
Maintaining adequate hydration is also a foundational and immediate step, especially for patients whose high count is largely due to dehydration. Consuming sufficient fluids helps dilute the blood, reducing the hematocrit and whole blood viscosity.
For cases where the red blood cell count is dangerously high and poses an immediate threat of thrombosis, a procedure called therapeutic phlebotomy may be performed. This involves the controlled removal of a unit of blood to rapidly decrease the red blood cell volume and lower the blood’s viscosity.
Treatment must also include addressing underlying conditions that contribute to the problem, such as using Continuous Positive Airway Pressure (CPAP) therapy for sleep apnea. Regular monitoring of hematological parameters alongside HbA1c is recommended to ensure the count is within a safe range. These comprehensive strategies are necessary to protect the patient from the severe complications associated with thickened blood.