Corrected Magnesium Calculator

Created by Kacper Pawlik, MD
Reviewed by Bogna Szyk, Aleksandra Zając, MD and Steven Wooding
Based on research by
M H Kroll, R J Elin Relationships between Magnesium and Protein Concentrations in Serum Clinical Chemistry (Feb 1985)
Last updated: Jun 05, 2023

This calculator will help you get a corrected magnesium level in a patient with low albumin (hypoalbuminemia). In the text below, you will discover why we should perform magnesium for albumin correction, how to do it, and, for curious readers, what the formula looks like! You will need only the lab results of the patient's serum magnesium and albumin level.

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. If any health condition bothers you, consult a physician.

What is the corrected magnesium?

Magnesium plays a crucial role in our bodies. It works as a catalysator of many processes, enables the contraction of cardiomyocytes, and stabilizes platelets in our blood. The physiological magnesium concentration in human serum is around 0.65-1.25 mmol/L. A lower magnesium level is called hypomagnesemia. 70% of serum magnesium is in a free, ionized form of Mg2+ cations, and the other 30% is bound with proteins, mainly albumins.

The serum magnesium level test measures 100% of serum magnesium, but only the first, free-form, is biologically active. In other words, solely the deficiency of the first form may cause clinical symptoms as listed below. It leads us to the problem of false hypomagnesemia that can be present in patients with low albumin level (hypoalbuminemia).

A low albumin level decreases the amount of magnesium bound with serum proteins, causing lower serum magnesium level test results. Our calculator will help you correct the serum magnesium level in a patient with hypoalbuminemia.

It is also worth noting that the serum magnesium level does not reflect its intracellular level, and there might be a deficit of magnesium in our body even when the serum magnesium level is in a physiological range.

There are many other examples of certain biological conditions altering lab results. To learn more about it, please check out our sodium correction and corrected calcium calculators.

What is the magnesium correction for albumin formula?

Although there is no general agreement on how we should achieve the magnesium correction for albumin, the following equation has been proposed by Martin H. Kroll and Ronald J. Elin and published in an article from 1985 titled: “Relationships between Magnesium and Protein Concentrations in Serum”.

corrected magnesium = serum_magnesium + 0.005 × (40 - albumin level)

How to use the corrected magnesium calculator

To find the corrected magnesium level:

  1. Insert the patient’s lab result of magnesium level in the "Patient’s magnesium" field. Be careful to notice the units of the test and select the correct one before entering the value.

  2. Type in the patient’s serum albumin level in a unit of your choice (usually g/L or g/dL).

  3. Our calculator will perform magnesium correction for albumin for you!

  4. Just write down the result from the "Corrected magnesium" section.

💡 You might also find our anion gap calculator interesting.

The problem of hypoalbuminemia

Albumins are the main proteins of human serum. They serve many functions in our bodies, such as maintaining oncotic blood pressure, regulating pH, and transporting hormones, cations (including magnesium), fatty acids, bilirubin, and many pharmaceuticals.

Hypoalbuminemia is a state of a deficit of the albumins, commonly defined as a serum albumin level below 35 g/L. It can be caused by many factors, including:

  • Undernutrition;
  • Liver failure (in cirrhosis or chronic hepatitis);
  • Nephrotic syndrome;
  • Protein-losing enteropathy; and
  • Severe inflammation.

The most common symptom of hypoalbuminemia is generalized edema caused by low oncotic blood pressure.

When should I suspect hypomagnesemia?

Unfortunately, symptoms of hypomagnesemia are rather unspecific. Low magnesium levels can manifest in many medical conditions:

  • Hypocalcemia, hypokalemia, and hypophosphatemia resistant to treatment;
  • Heart arrhythmias and ECG changes;
  • Muscle weakness;
  • Limb tremor; and
  • Tetany (involuntary contraction of muscles).

In all of these cases, a serum magnesium level test should be considered during a diagnostic process.

Kacper Pawlik, MD
Patient's magnesium
Patient's albumin
Corrected magnesium
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