Hemoglobin Instability in Chronic Care Patients:  Pseudoanemia and Stress Reactions

Hemoglobin Instability in Chronic Care Patients:  Pseudoanemia and Stress Reactions

Unlocking the Power of Posture and Stress:  Understanding Impact on Blood Indices and Anemia Management


As a service provider catering to the geriatric population, dealing with anemia among your residents is common. However, there is a perplexing condition known as pseudoanemia that can create confusion. Despite having a normal or even increased red blood cell mass, the patient’s hemoglobin levels appear low. This condition arises due to postural fluid shift resulting in a diluted concentration of red blood cells in the blood and alterations in plasma volume when patients have been at rest for some time, such as when in bed at night, or if they have limited mobility. Fortunately, one simple solution exists to resolve this issue: changing the patient’s posture to an upright position at least 30 minutes before their draw. 

The Problem 

A patient’s blood is drawn early in the morning and the Complete Blood Count (CBC) shows a “critical value” for Hemoglobin and/or Hematocrit. The patient is admitted to the hospital for a potential blood transfusion. However, when the hospital reevaluates the CBC, the Hemoglobin and/or Hematocrit levels are found to be higher and not critical, leading to no need for a transfusion. A worse situation can arise if a pseudoanemic patient is kept reclined and the Hgb/Hct has not had time to correct, resulting in an unnecessary transfusion. 

Study Conclusions

  • Results confirm that changes in posture affect blood indices. Posture alters hydrostatic pressure, which influences fluid movement between interstitial and intravascular spaces, leading to physiological fluctuations in blood volume.
  • Postural changes can significantly impact Hgb/Hct levels, which may be wrongly interpreted as blood loss or acute anemia, leading to unnecessary diagnostic and therapeutic procedures. However, these changes actually reflect postural pseudoanemia, a natural physiological response to shifts between standing and lying positions. Such changes can be exaggerated in patients with low albumins.

Medical Director Recommendation

To avoid pseudoanemic critical values and unnecessary treatments, ensure the patient remains upright, ideally engaging in light walking, or sitting upright for 30 minutes before blood collection. This will typically help reverse fluid shifts, leading to a more accurate Hgb/Hct measurement.

Stress Reactions

Stress reactions represent a phenomenon somewhat contrary to pseudoanemia, often occurring when a patient undergoes physiological or psychological stress, such as during unforeseen transportation to a hospital or another transfusion center. It is widely recognized that an adrenaline-fueled stress reaction can lead to a temporary increase in Hgb/Hct levels, a response commonly associated with the “fight or flight” reaction. In cases where a patient is genuinely anemic, this stress-induced surge in Hgb/Hct can push these values into the normal range by the time the patient arrives at the transfusion center. Consequently, these seemingly normal values might lead the transfusion center to decline the patient’s transfusion request, resulting in their return to the facility without the required treatment.

Additionally, it’s important to consider another factor in this scenario. Transfusion center phlebotomists may encounter challenges when drawing blood from chronic care patients, often due to limited venous access. In such cases, they may resort to the overuse of a tourniquet, a practice that can also falsely elevate Hgb/Hct levels into the normal range, further complicating the assessment of the patient’s true transfusion needs.

The Problem

These patients are often drawn at the facility and have been upright for hours, so this is not the same as pseudoanemia. They actually are anemic and do need a transfusion but after transport are showing falsely as being normal, possibly due to stress or phlebotomy technique. As a clue, they often have a recent history of multiple anemia-range Hgb/Hct values. 

Medical Director Recommendation

These patients should not be sent back to the facility immediately but should be held at quiet rest at the transfusion site and retested at some reasonable interval to confirm they do or don’t actually need a transfusion. In the event that they are sent back to the client facility without undergoing a transfusion, it is imperative for the facility to promptly order a stat Hgb/Hct test to provide confirmation.

Messaging Approved by Laboratory Directors:  Dr. John Morgan Brown, Dr. Russell Kerschmann, and Dr. Peter Patterson 


  • Rita H. Khoury, MD1; Vasilios Velmahos, MD2; Asha Gandhi, BS1; BP. Salmon, MS1; Rudy Quiba, BA1; Peter Gudaitis, BA1; Dauna Gudaitis, BA1
  • Department of Laboratory, Aculabs, Inc., East Brunswick, New Jersey
  • Department of Medicine, New Jersey Infectious Diseases Associates, Edison
  • (2011) Abstracts and Case Studies From the College of American Pathologists 2011 Annual Meeting (CAP ’11). Archives of Pathology & Laboratory Medicine: September 2011, Vol. 135, No. 9, pp. 1102-1230