Serum ionized calcium, however, may range from normal to slightly reduced in less severely affected horses. Serum creatinine phosphokinase may be elevated in more severely affected patients. Other laboratory findings include a tendency toward acidosis and mild hypokalemia. Hyperglycemia is frequently present in the early stages of the disease. Serum urea nitrogen and creatinine are initially elevated but return to normal with recovery from the disease.
Many horses have a positive test for fecal occult blood.
Urinalysis frequently reveals microscopic hematuria. Epithelial cells are occasionally seen but casts are seldom present. The urine specific gravity is low and may range from 1.003 to 1.010 even though the horse is dehydrated. Cantharidin toxicosis should be considered when signs of abdominal pain, depression or pollakiuria are exhibited by horses ingesting alfalfa hay or alfalfa feed products. A presumptive diagnosis can be made when beetles are found in the hay and horses exhibit clinical signs and laboratory abnormalities compatible with cantharidin toxicosis.