To correct calcium levels in patients with low serum albumin, you need to calculate the corrected calcium using a specific formula.
Corrected Calcium Calculation
The formula to calculate corrected calcium is:
Corrected calcium (mg/dL) = measured total Ca (mg/dL) + 0.8 (4.0 - serum albumin [g/dL])
- Where 4.0 represents the average albumin level.
This formula adjusts the measured total calcium level to account for the effect of low albumin on calcium binding.
Example of Corrected Calcium Calculation
Here's a step-by-step example:
- Measure Total Calcium: Measure the patient's total calcium level in mg/dL. Let's say it's 7.5 mg/dL.
- Measure Serum Albumin: Measure the patient's serum albumin level in g/dL. Let's say it's 2.5 g/dL.
- Apply the Formula:
- Corrected Calcium = 7.5 + 0.8 (4.0 - 2.5)
- Corrected Calcium = 7.5 + 0.8 (1.5)
- Corrected Calcium = 7.5 + 1.2
- Corrected Calcium = 8.7 mg/dL
In this example, the corrected calcium level is 8.7 mg/dL.
Why Correct Calcium?
It is important to correct calcium levels when serum albumin is low because albumin binds to calcium in the blood. When albumin levels are low, a smaller proportion of calcium is bound, leading to a falsely low measurement of total calcium. Correcting the calcium level provides a more accurate assessment of physiologically active calcium.
