Complete blood count (CBC) - Hemoglobin and hematocrit: Nursing

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Content Reviewers

Lisa Miklush PhD, RN, CNS,Yifan Xiao, MD,Gabrielle Proper, RN, BScN, MN

A client comes to the outpatient clinic and reports feeling fatigued, weak, and is experiencing frequent palpitations. On assessment, the client’s skin and mucous membranes look pale and their extremities feel cold. Based on these findings, a complete blood count, or CBC, is ordered to check their hemoglobin and hematocrit.

Now, hemoglobin, abbreviated as Hgb or Hb, and hematocrit abbreviated as Hct or sometimes Crit, are usually measured as part of a CBC, and they provide an indirect way to measure red blood cells or RBCs. Hemoglobin is an iron-containing protein found in RBCs, which allows them to carry oxygen from the lungs to peripheral tissues. The hematocrit represents the percentage of packed RBCs, also referred to as the Packed Cell Volume or PVC, in whole blood, that’s obtained after centrifuging part of the sample to allow for complete sedimentation of the RBCs.

The normal values of hemoglobin and hematocrit differ between the sexes. This is because in females, RBC production is stimulated by erythropoietin only, while in males, androgens provide additional stimulation for RBC production. So, in adult males, hemoglobin normally ranges from 14.0 to 18.0 g/dL, while in adult females it normally ranges from 12.0 to 15.0 g/dL. Hematocrit in males ranges from 41.0% to 51.0%, while in females it ranges from 36.0% to 45.0%.

Typically, the hematocrit will be about three times the value of hemoglobin. As an example, if a client’s hemoglobin is 14.0 g/dL, their expected hematocrit would be about 42%.

Alright, there are certain conditions that can alter a client’s hemoglobin and hematocrit.

When the number of RBCs increases, like in polycythemia vera, a condition where the bone marrow produces too many RBCs, hemoglobin also increases. These additional cells also increase the percentage of RBCs, which means that the hematocrit will go up as well.

Alternatively if the amount of fluid in the blood decreases, like with dehydration, the concentration of RBCs increases, and the hemoglobin and hematocrit will also increase.