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Albumin-Corrected Magnesium

Enter total serum magnesium, albumin, and unit to estimate corrected magnesium concentration. Particularly useful when albumin is low and ionized magnesium is unavailable.

Choose the same unit reported by the laboratory.

If albumin is normal (~3.5–5.0 g/dL), corrected and measured magnesium will be similar.

Corrected magnesium

1.45 mg/dL

Corrected magnesium (SI)

0.60 mmol/L

Corrected magnesium below normal (hypomagnesemia)

Evaluate for gastrointestinal or renal losses, poor intake, medications (diuretics, PPIs). Correct magnesium cautiously and monitor for arrhythmias.

How to Use This Calculator

1

Collect total magnesium and albumin

Use the same blood sample when possible. Note that ionized magnesium measurement is superior when available.

2

Select matching units

Find out whether the laboratory reports magnesium in mg/dL or mmol/L. The calculator converts between units automatically.

3

Interpret results alongside clinical findings

Corrected magnesium helps screen for abnormalities, but symptoms and ionized magnesium guide definitive management.

Formula

Corrected Mg (mg/dL) = Total Mg + 0.05 × (3.5 − Albumin)

Corrected Mg (mmol/L) = Corrected Mg (mg/dL) ÷ 2.43

Albumin in g/dL. Coefficient (0.05) approximates the albumin-bound fraction of magnesium.

Full Description

Total serum magnesium reflects both bound and ionized fractions. Hypoalbuminemia reduces bound magnesium, lowering total levels without affecting ionized magnesium. Correcting for albumin provides a better estimate of physiologically active magnesium when direct ionized measurement is unavailable. Use caution in critically ill patients, since the correction is an approximation and ionized measurements should be obtained whenever possible.

Frequently Asked Questions

Is this correction widely validated?

Several studies propose similar formulas, but evidence is limited. Prefer ionized magnesium for precise management, especially in ICU settings.

Why use 0.05 as the coefficient?

It approximates the change in total magnesium (mg/dL) per 1 g/dL change in albumin. Some references use 0.1; adjust per institutional practice.

How is hypermagnesemia treated?

Mild cases respond to stopping magnesium sources and fluids. Severe cases require IV calcium, loop diuretics, or dialysis in renal failure.

When should I rely on ionized magnesium?

Evaluate ionized magnesium in symptomatic patients, those with critical illness, or when corrected and clinical findings do not align.