Hypoalbuminemia Corrected Calcium Calculator

Variables and formulas

The above calculator corrects calcium levels in patients with hypoalbuminemia. There are three fields to input, either in standard units (first tab) or SI units (second tab).

■ Serum calcium – in mg/dL or mmol/L;

■ Albumin (patient value) – in g/dL or g/L;

■ Normal albumin – set default at 4 g/dL or 40g/L.

The formula used is the following:

Corrected Calcium = Serum Calcium (mg/dL) + 0.8 x (Normal albuminemia (g/dL) – Patient albuminemia (g/dL))

Which can also be written like:

Corrected Calcium = Serum Calcium (mg/dL) + 0.8 x (4 g/dL – Patient albuminemia (g/dL))

If the SI units are used, the equations become:

Corrected Calcium = Serum Calcium (mmol/L) + 0.02 x (Normal albuminemia (g/L) – Patient albuminemia (g/L))

Corrected Calcium = Serum Calcium (mmol/L) + 0.02 x (40 g/L – Patient albuminemia (g/L))

Because albumin is the protein that binds calcium in the blood stream, the calcium level needs to be corrected if the albumin levels are higher (hyper-) or lower (hypo-) than normal. The reference range for albumin is between 3.5 and 5.5 g/dL (35 – 55 g/L).

The calcium correction helps determine the accurate Ca levels, as if albumin were in the normal range:

■ In hypoalbuminemia, corrected calcium (actual value) tends to be higher than tested calcium;

■ In hyperalbuminemia, corrected calcium tends to be lower than tested calcium.

Normal calcium levels vary between 8.5-10.5 mg/dL or 2.1-2.6 mmol/L depending on the testing laboratory.

Implications of hypoalbuminemia

Hypoalbuminemia is defined as low blood albumin levels (<3.5 g/dL). Albumin accounts for 50-60% of blood proteins and is involved in the transport of bilirubin, ions, hormones, fatty acids or exogenous substances, like medication.

If albumin levels are lower than normal, these substances remain free in the plasma and tend to go faster through the hepatic metabolism because of that.

Another role of blood proteins is that of sustaining the balance between osmotic and hydrostatic pressure and in preventing edema.

Low albumin levels can be caused by liver disease (especially cirrhosis), nephrotic syndrome, heart failure, burns, malnutrition etc.

Hypoalbuminemia can be found in many acute and chronic medical conditions and is a common indicator of the acute and chronic inflammatory response.

Original source

Payne RB, Little AJ, Williams RB, Milner Jr. Interpretation of Serum Calcium in Patients with Abnormal Serum Proteins. Br Med J. 1973; 4(5893): 643–646.

Other references

1. Parent X, Spielmann C, Hanser AM. Corrected calcium: calcium status underestimation in non-hypoalbuminemic patients and in hypercalcemic patients. Ann Biol Clin (Paris). 2009; 67(4):411-8.

2. Hall J. (2015) Guyton and Hall Textbook of Medical Physiology 13th ed. Elsevier Health Sciences.