Hypercalcemia is defined as a serum or plasma total calcium level exceeding the normal level. Reference ranges vary considerably among laboratories however a serum calcium concentration > 12mg/dl is considered to be a clinically important elevation and a repeated calcium elevation warrants clinical investigation. Routine calcium levels reported on chemistry profiles are Total calcium, of which 50% is ionized (the metabolically active form) , 40% is protein bound (to albumin) and 10% calcium complexes. In the dog serum calcium concentration is adjusted for albumin level by subtracting the albumin level from the total Ca++ level and adding 3.5.;this yields a corrected calcium level in mg/dl. This method is not accurate in cats. Recently, (2005) it has been suggested that ionized calcium must be measured directly in order to obtain the most accurate level and prevent misdiagnosis of disease especially in dogs with chronic renal failure.