You just got a copy of your horse’s blood tests. The veterinarian said everything was “normal.” Then you start to look at the actual numbers and notice some appear to be barely normal. For example, your horse’s insulin level is 29, and the lab says it shouldn’t be any higher than 30. Does it mean anything' Maybe.
Blood chemistry panels measure proteins and various other substances in the blood. Generally speaking, they are indicators to how well the organs are functioning and such things as specific types of tissue damage (e.g. muscles) and hydration. Chemistries are difficult to interpret, but we’ve summarized the possible significance of some results in our chart (See sidebar below).
Blood-cell counts, also sometimes called hematology, are counts and characteristics of blood cells. Your cell count results will give details of the red blood cells (RBC). The most important numbers here are the RBC count and the hemoglobin, which are the best indicators of anemia.
Red-cell counts and hemoglobin at the high end of normal usually mean the horse was somewhat dehydrated. You may also get results like this if the horse is upset, excited or worked recently, and extremely fit horses tend to run in the high ranges. Anemia is a lower-than-normal red count and hemoglobin. Older, “cold-blooded,” ill, parasite-infested, hypothyroid horses and “pasture-ornament” horses often tend to run toward the low end of normal.
However, even some fit horses can have red counts and hemoglobins toward the low end when at rest because their hearts are just so efficient at pumping large volumes of blood that they don’t need as many red cells to carry oxygen when they aren’t exercising. Nutritional deficiencies can do it, too. Obviously some of these reasons represent abnormal/disease states and others don’t.
It’s important to keep the “big picture” in mind — as in whether the horse appears healthy and vigorous, performs well, etc. — to avoid getting upset for no reason. It’s also a good general indicator whether other tests need to be done or not. In most cases, especially if this is the only questionable finding on the blood work, the best advice is just to keep an eye on it and retest.
Platelets may just be mentioned with a comment like “adequate,” or an actual platelet count can be done. Platelet counts toward the high end are rare and of no concern until outside normal ranges. If at the low end, it could be a sign of an infection, a clotting disorder or a drug reaction.
White blood cell counts can be among the most difficult things to interpret. It is the total number of white cells of all types and the total number of each individual type, called the absolute counts, that are the important figures. However, the different cell types (neutrophil, lymphocyte, monocyte, eosinophil, basophil, bands) are usually reported as percentages. Neutrophils and lymphocytes should be present in approximately equal amounts with small numbers, if any, of the other cells.
If your total count is low or high normal, but all the cells present are in normal percentages, there’s no need for concern. More often than not though, it will be a change in the numbers of one or more cell type that puts your total count out of whack. This is where it gets tricky, and you must figure out those absolute counts.
Upper or lower ends of the normal range could be normal for your horse or could be an early warning sign. The range of cell counts in horses is genuinely wide so what is normal for one won’t be for another.
To interpret your numbers accurately, you need to look at changes from what’s been established previously to be normal for your horse. You may be able to differentiate between the two situations by looking for patterns of changes in related tests. We suggest you consider repeating the tests in a few weeks to see what’s going on and then discuss the “big picture” with your veterinarian.