Before testing for HYPP, a veterinarian is advised to consider a differential diagnosis. Azotemia must be ruled out. The serum potassium level is an important indicator. There is a field test which allows a veterinarian to observe the horse during a hyperkalemic episode. The affected horse may not go down, but may instead, exhibit such signs as continuous muscle fasciculation plus muscle spasm, dyspnea or weakness.
Muscle fasciculation is the main sign of the affected horse.
These may be fine or gross, involving large areas of the body. Other commonly observed signs were sweating, discomfort, weakness, prolapse of the third eyelid, and spasm of the facial muscles. There is not consistent change in heart rate. Generally the horse has an elevated respiratory rate. These researchers found that HYPP does predispose to other problems such as unexplained recumbency during transportation and abrasions-probably representing sequelae to unobserved attacks.