How much blood is in a cat’s body?

The body of a 5 kg (12 lbs) domestic cat contains about 12 fluid ounces of blood, which is 330 mL. A soft drink can contains about the same amount (half a pint) . As the blood pumps the blood from the heart, the blood pressure is highest in the arteries carrying blood away from the heart and lowest in the veins when the blood returns to the heart. The normal systolic pressure in dogs and cats is in the 120-130 mmHg range. The blood passes around their body once every 11 seconds.

Domestic cat circulatory system
Domestic cat circulatory system. Source: msdvetmanual.com
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About cat blood

When people feel the pulse of a cat or a human they feel the elastic walls of the artery expand and contract as the heart pushes blood through them. The veins do not have a pulse. They contain non-return valves.

About 15 to 20% of a cat’s blood is in their brain despite being a relatively small part of the overall weight of a domestic cat. When a cat is using her muscles to a maximum about 90% of her blood is diverted into them whereas when the muscles are resting about 30% to 40% of the blood is fed to them.

Hormones and nerves control the delivery of blood and the amount that the various regions of the body receive. They cause the arterioles to dilate which increases blood flow through them. Arterioles are small diameter blood vessels with muscular walls which branch out into the various parts and extremities of the body.

Cat's heart
Cat’s heart. Image: msdvetmanual.com.

Most of a cat’s blood is called plasma which is pale-yellow in colour. This is the transport portion of the blood that carries nutrients from the digestive system to parts of the body, and it transports waste from them. Between 30 and 40% of blood is made up of red blood cells and the remainder is white blood cells and platelets. White blood cells defend the body against parasites and microbes. They also clear waste from injuries and detoxify substances created during an allergic reaction. They produce antibodies which fight disease causing infections. The disc-shaped platelets help to clot the blood when it bleeds through a wound.

In adult cats the bone marrow produces blood cells while in kittens the liver and spleen do it. The red blood cells, which have a lifespan of 2-6 weeks, carry oxygen to the cells. They do this by the oxygen attaching to a protein called haemoglobin in the cells which is red in colour and when attached it is called oxyhaemoglobin. In every red blood cell there are 270 million haemoglobin molecules. Oxygen is delivered to the cells of the body through the capillary walls in cell tissue. Carbon dioxide diffuses into the veins where it attaches to haemoglobin to make methaemoglobin which is blue-red in colour.

Blood type

Domestic cats have three types of blood: A, B, and AB. The type of blood that a cat has depends on where they live but the majority have type A. In Switzerland almost all random bred cats have type A blood. In Britain, Austria and Holland, 97% of random bred cats have typed A blood. In Germany it is 94% and in Italy it is 87%. In the USA almost all random bred cats have type A blood but in New England it is 95%.

Of the purebred cats, 25% of the population of the Exotic Shorthair and the Cornish Rex cats have type A blood. Fifty-percent of the Devon Rex and British Shorthair population have type A blood.

Anemia

In anaemic cats, the number of red blood cells falls. Anaemic cats look pale with bluish gums because they have lost the red colour of red blood cells. A bad flea infestation and injury are two examples that can cause anaemia albeit temporarily, hopefully. Also, certain illnesses can be a barrier to the production of new red blood cells. These illnesses include feline leukaemia virus, kidney failure, poisoning and deficiencies in the nutrition. The most prevalent heart disease in cats is hypertrophic cardiomyopathy which is an inherited disease for the Bengal cat by the way.

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