What is the formula for corrected calcium?

The formula for corrected calcium is essential in clinical practice, especially when interpreting calcium levels in the presence of altered albumin levels. The correct answer states that corrected calcium is calculated by taking the measured calcium and adding 0.8 times the difference between 4 and the patient's albumin level.

Albumin is a protein that binds calcium in the blood, and changes in serum albumin levels can affect total calcium measurements. When albumin decreases, total calcium levels may also appear low, even if ionized calcium (the physiologically active form) is normal. The factor of 0.8 is used because it approximates the calcium binding capacity of albumin; for every 1 g/dL decrease in albumin, the total calcium level needs to be adjusted upward by 0.8 mg/dL to reflect the physiological calcium status accurately.

Thus, this formula allows healthcare providers to get a more accurate picture of a patient's calcium status in relation to albumin levels, making it an important tool for diagnosis and treatment planning.