Haematocrit

The haematocrit measures the percentage of red blood cells in your dog’s blood. This lab value shows how well the blood can transport oxygen; a low value indicates anaemia, while a high one often points to dehydration.

Why is the haematocrit important for my dog?

Red blood cells transport oxygen from the lungs to the organs. The haematocrit tells you whether there are enough of them present. For healthy dogs, the MSD Veterinary Manual cites 35 to 57 percent. Other labs use narrower ranges, for example Laboklin at 44 to 52 percent. There is therefore no single correct range: the reference range of the lab that performed the measurement applies.

Sighthounds are the well-known exception. Their haematocrit is naturally higher, averaging around 58 to 61 percent in young Greyhounds. A value that would be notable in other breeds is normal for them.

An example from practice: Your female dog has seemed tired for days, is eating poorly and has pale gums. The vet measures a haematocrit of 25 percent, significantly too low. The blood cannot transport enough oxygen.

When does the vet measure the haematocrit?

The haematocrit is a standard component of the full blood count. It is measured particularly when anaemia is suspected, after surgeries involving blood loss, or if your dog shows symptoms such as weakness and pale mucous membranes.

It is also included in routine check-ups for older dogs; kidney failure often leads to insidious anaemia, which owners only notice late on.

What does a haematocrit that is too low mean?

If the haematocrit falls below the lab’s reference range, this is referred to as anaemia. The most common causes are chronic kidney diseases; the kidneys then produce too little erythropoietin, the hormone responsible for blood formation.

Other causes: autoimmune diseases in which the body destroys its own blood cells, internal bleeding due to tumours or parasitic infestation that silently drains blood over months. A haematocrit below 20 percent is considered severe anaemia and requires immediate veterinary treatment. This threshold is not strict: how dangerous a value is also depends on how quickly it has dropped.

What does a haematocrit that is too high mean?

A haematocrit above the reference range is usually caused by dehydration, meaning the blood becomes “thickened”. This is typical after diarrhoea or vomiting, or when older dogs do not drink enough.

Rarely, a true overproduction of red blood cells lies behind it, for example in heart defects or lung diseases. The body then attempts to compensate for the lack of oxygen by increasing the number of transport cells.

What symptoms do dogs show with abnormal values?

With low values, you will notice: rapid exhaustion after short walks, pale or whitish gums, heavy breathing even with minimal exertion. Some dogs eat earth or lick metal objects, a sign of iron deficiency.

With high values due to dehydration: sunken eyes, dry gums, the skin fold on the neck remains standing after being lifted. The blood becomes viscous, and paradoxically, circulation worsens despite the high cell count.

How is the haematocrit measured?

A small blood sample from the leg vein suffices. The blood is centrifuged, the heavier red blood cells settle at the bottom, and the clear plasma floats on top. The proportion of the red layer yields the haematocrit percentage.

Modern lab devices measure automatically and deliver the result within minutes. Some vet practices have such devices on site, while others send the sample to external labs.

How are abnormal values treated?

In cases of severe anaemia, a blood transfusion may become necessary, particularly after acute blood loss. There is no fixed number at which transfusion begins. The overall picture counts, comprising the value, the rate of decline and symptoms such as weakness or shortness of breath. The underlying disease must be treated in parallel: kidney therapy for kidney failure, immunosuppressants for autoimmune diseases.

In cases of dehydration, fluid administration via infusions helps. Older dogs that drink poorly often require regular check-ups; kidney values and haematocrit go hand in hand here.