Corrected Magnesium Calculator
Adjust serum magnesium for low albumin using the Kroll and Elin formula with mg/dL, mmol/L, and g/L unit support.
What Is Corrected Magnesium?
Serum magnesium tests include both free ionized magnesium and protein-bound fractions. When albumin is low (hypoalbuminemia), measured magnesium can underestimate the biologically active level. Corrected magnesium adjusts for albumin using the Kroll and Elin relationship. See also the Corrected Calcium Calculator and Corrected Sodium Calculator.
Formula
In SI units (mmol/L magnesium, g/L albumin):
$$\text{Corrected Mg} = \text{Measured Mg} + 0.005 \times (40 - \text{Albumin})$$
In conventional units (mg/dL magnesium, g/dL albumin), the equivalent coefficient is 0.05 with a reference albumin of 4 g/dL.
Clinical Context
Typical serum magnesium ranges are about 0.65 to 1.25 mmol/L (1.7 to 2.2 mg/dL). Hypomagnesemia can cause arrhythmias, muscle cramps, and refractory hypokalemia or hypocalcemia. This correction is most useful when albumin is low from malnutrition, liver disease, or nephrotic syndrome.
Frequently Asked Questions
Why correct magnesium for albumin?
Roughly 30% of serum magnesium is protein bound, mainly to albumin. Low albumin lowers total magnesium without necessarily reducing free ionized magnesium.
What reference albumin level is used?
The default reference is 4 g/dL (40 g/L). You can change this if your laboratory uses a different normal range.
Does ionized magnesium replace correction?
Ionized magnesium directly measures the active fraction and is ideal when available. Corrected magnesium is a useful estimate when only total magnesium and albumin are reported.
What symptoms suggest hypomagnesemia?
Common signs include muscle weakness, tremor, tetany, arrhythmias, and electrolyte abnormalities that resist treatment until magnesium is repleted.
Can I use this in kidney failure?
Interpret magnesium carefully in renal disease. Albumin correction helps context, but dosing and monitoring require clinician guidance.
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