There are a few areas on the body that provide important information regarding the state of a horse's circulatory health. These areas include the gums, the pink membrane inside the nostril, the whites of the eyes, and the pink inner vulvar membranes of mares. That said, the simple act of evaluating the color of your horse's gums is actually a very important skill for better understanding your horse.

Dark mucous membranes can indicate a variety of disease processes. Horses that are dehydrated often have dark-appearing gums and slow refill times. When examining horses with darkly pigmented gums, keep in mind that some horses (especially dark bay colored) have areas of their gums which are darkly pigmented. This pigment can change the appearance of the gums and make them hard to interpret. Occasionally, horses will eat substances that stain the gums. This is especially common in grazing horses.