Red blood cells (RBC)
Blood count (CBC) ·Also called: RBC, erythrocytes, red cell count, red blood cell count
What it is
Red blood cells are the disc-shaped cells that carry oxygen from the lungs to every tissue in the body. The RBC count is simply how many of them the analyser found per unit of blood. It is reported alongside haemoglobin and haematocrit, which measure the same population a different way.
Why your vet measures it
Oxygen delivery is the single most basic thing blood does, so this number sits near the top of almost every panel. It is also one of the few values that changes visibly in the animal: a genuinely low red cell count shows up as pale gums, low stamina and faster breathing.
What a high result can mean
- Dehydration — the cells are normal in number but the fluid around them has shrunk, concentrating the sample
- Excitement or a struggle during the blood draw, which contracts the spleen and pushes stored cells into circulation (common in cats)
- Long-term low oxygen from heart or lung disease, prompting the marrow to make extra cells
- Polycythaemia, an uncommon disorder of overproduction
What a low result can mean
- Bleeding — from trauma, a tumour, a stomach ulcer, or heavy flea or tick burden
- Red cells being destroyed faster than they are replaced, as in immune-mediated haemolytic anaemia or some toxins
- Reduced production, seen with chronic kidney disease, bone marrow disorders, and FeLV in cats
Dogs and cats differ
Greyhounds and other sighthounds naturally run red cell counts above the generic canine range, and a value flagged 'high' in a fit Greyhound is often just breed. Cats, by contrast, have smaller red cells and a lower normal count than dogs, and their spleen releases a burst of cells when they are stressed — so a nervous cat's sample can read higher than the same cat at home.
Questions worth asking your vet
- Is this a real change, or could dehydration or stress at the visit explain it?
- How does it compare with my pet's previous results rather than the printed range?
- If it is low, do we know whether my pet is losing blood, destroying it, or not making it?
Related terms
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