A patient on hemodialysis is experiencing fatigue. Which of the following could be a contributing factor?

Fatigue in patients undergoing hemodialysis is often linked to anemia, which is frequently characterized by a low red blood cell count. In these patients, the kidneys are not functioning adequately to produce sufficient erythropoietin, a hormone that stimulates the production of red blood cells in the bone marrow. Consequently, when the red blood cell count is low, the oxygen-carrying capacity of the blood diminishes, leading to fatigue and weakness.

While other factors such as high or low levels of certain minerals or high blood pressure can affect overall health, they do not have a direct and immediate link to fatigue in the same way that low red blood cell count does. For instance, high iron levels can indicate sufficient iron stores or overloading but typically wouldn't directly cause fatigue. Low calcium could lead to other symptoms such as muscle cramps or spasms but is not primarily associated with fatigue. High blood pressure, while a concern in dialysis patients, generally doesn’t manifest primarily as fatigue unless it is severely uncontrolled or leading to other complications.

Thus, the connection between low red blood cell count and fatigue makes it the most relevant factor in this scenario.