Empeiria

Erythrocyte count

Also known as RBC, red blood cell count, red cell count

cell count · no single molecular formula

LOINC 789-8 code verified whole_blood 10*6/uL

What this substance is

A red blood cell is a cell, not a compound. The cell type is recorded in the anatomy graph as CL:0000232; there is no molecular identity to give.

Reference ranges

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This open edition shows a range only where a public-domain or openly licensed source states one, and none does for this marker yet. Compare your result with the range printed on your own lab report.

How it is measured

In practice

A health worker takes a small amount of blood from a vein in your arm with a thin needle. It usually takes less than five minutes. You do not need to do anything special to prepare. The red cell count is almost always done as part of a complete blood count (CBC).

Venous whole blood collected by venipuncture into an EDTA tube (NHANES uses a 3- or 4-mL EDTA tube; liquid EDTA gives a 1-2% dilution effect). The RBC count is almost always reported as part of a CBC run on the EDTA sample. No patient preparation is required.

Where: laboratory

Sources: Laboratory Procedure Manual, Complete Blood Count (NHANES 2007-2008), CDC National Center for Health Statistics; Red Blood Cell (RBC) Count, MedlinePlus (U.S. National Library of Medicine) cited · not yet checked by a person

In the lab

impedance

Electrical impedance (Coulter principle) count

The machine pushes very watered-down blood through a tiny hole one cell at a time. Each red cell makes a small electrical blip, and the machine counts the blips.

Diluted blood is drawn through a small aperture carrying an electric current; each cell transiently raises the electrical resistance, producing a pulse, and the pulses are counted and multiplied by a calibration constant.

  • Read by: Electrical resistance (impedance) pulses at the aperture

What can throw it off

  • Very high white cell count
  • Agglutinated red cells
Why labs disagree: The count is multiplied by an analyser calibration constant, and different measurement procedures give different results, so labs are advised to set intervals on their own equipment. RBC counts also differ significantly between men and women.

Sources: Arbiol-Roca A et al. Reference intervals for a complete blood count on an automated haematology analyser Sysmex XN in healthy adults from the southern metropolitan area of Barcelona. EJIFCC 2018 (PMC5949618, open access); CDC NHANES 2011-2012 Laboratory Procedure Manual: Complete Blood Count using Coulter HMX cited · not yet checked by a person

What it reports on

Associated symptoms

Conditions this marker features in

When high
  • high Carrier of beta-thalassaemia · supportive
    The red cell count tends to be high for how small the cells are. A high count with a low MCV points towards beta-thalassaemia trait rather than iron deficiency.
  • high Too many red blood cells · supportive
    A higher than normal red cell count can come from polycythaemia vera, low blood oxygen, smoking or dehydration.

Ordered as part of

cbc