The relationship between total and ionized calcium in the blood sheep when calcium levels are altered.

In a series of eight experiments attempts were made to change the levels of calcium in the blood of sheep by intravenous infusions of calcium, EDTA and thyrocalcitonin or changing the acid-base balance by various means. When total calcium levels changed these changes were mirrored closely by changes in the physiologically important ionized calcium fraction (r = 0.839). It is concluded that the total calcium determinations remain valuable indicators of changes in the physiological level of calcium in the blood.