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Adjusted Calcium

Only a small portion of total calcium measured in the blood, called “free calcium” or “ionized calcium,” is active in the body tissues. Generally speaking, total calcium levels are a good indicator of the proportion of free or ionized calcium. But this is not always the case. Low levels of albumin in the blood push down total calcium measurements, but not free calcium measurements. Albumin-adjusted calcium levels can therefore be calculated to give a more accurate picture of the proportion of free calcium.

Sometimes the proportion of free calcium needs to be directly measured at the body’s normal pH, due to changes in blood pH or the presence of calcium-binding agents, such as lactates. This measurement is called “adjusted ionized calcium (at pH 7.4).”

Albumin-adjusted total calcium levels and adjusted ionized calcium levels (at pH 7.4) are interpreted in the same way as total calcium levels (see those headings).

Term of the Week

Hot zone

A hot zone is a section of a facility (sometimes an entire facility or even a city district) where there is a high risk of contamination by patients with an infectious disease. All individuals entering a hot zone must respect appropriate protective measures. By analogy, “cold zone” and “warm zone” are used to refer to areas where there is no infected individual or only individuals suspected of having an infection.