Blood tests: a quick, accurate guide to your horse's health

Why do veterinarians take blood tests from a horse and what are they looking for? Dr Mac explains the basics of this crucial diagnostic tool

- Dr Mac

A veterinarian called out to examine a horse will often insert a needle into the animal’s jugular vein and take blood samples. In most cases, two samples will be taken – in a red-topped and purple-topped tube respectively. The former will be used for checking blood chemistry and diagnosing infectious diseases using serology (examination of blood serum), while the latter will be used to check the haematocrit and carry out blood smears. What does all this mean?

DIFFERENT TUBES, DIFFERENT TESTS

The red-topped tube contains no additives. The purple-topped tube contains an anticoagulant, which is a chemical that stops the blood from clotting. If you take a sample from this unclotted blood for centrifugation, or even leave the tube standing upright, the red blood cells will settle at the bottom of the tube. Above them will be the serum, a golden-yellow liquid without blood cells or clotting factors.