Corrected Magnesium Calculator

Measured Magnesium (Mg) Enter the measured serum magnesium level

Measured Albumin Enter the measured serum albumin level

Normal Albumin Reference Enter the normal reference albumin value for your lab

g/L

About Corrected Magnesium Calculation

Clinical Significance

Magnesium exists in three forms in the blood:

Ionized (Free) Magnesium: Biologically active form (55-70%)
Protein-bound Magnesium: Bound to albumin (20-30%)
Complexed Magnesium: Bound to anions like phosphate and citrate (5-15%)

Since approximately 30% of serum magnesium is bound to albumin, changes in albumin levels can affect measured magnesium values. The corrected magnesium calculation adjusts for this.

Magnesium Status	Serum Magnesium Level (mmol/L)	Corrected Magnesium Level (mmol/L)	Clinical Significance
Hypomagnesemia	< 0.75	< 0.70	Requires magnesium supplementation
Normal	0.75 - 1.0	0.70 - 0.95	Adequate magnesium levels
Mild Deficiency	0.5 - 0.75	0.45 - 0.70	May require supplementation
Moderate Deficiency	0.4 - 0.5	0.35 - 0.45	Usually requires IV magnesium
Severe Deficiency	< 0.4	< 0.35	Medical emergency
Hypermagnesemia	> 1.0	> 0.95	Monitor for toxicity

When to Use Corrected Magnesium

Patients with hypoalbuminemia (albumin < 35 g/L)
Critically ill patients
Patients with liver disease
Patients with nephrotic syndrome
Patients with malnutrition
Before initiating magnesium therapy
When measured magnesium is borderline normal but clinical suspicion is high

Normal Magnesium Range

Adults: 0.75 - 1.0 mmol/L (1.8 - 2.4 mg/dL)

Children: 0.7 - 0.95 mmol/L (1.7 - 2.3 mg/dL)

Note: Reference ranges may vary slightly between laboratories.

Hypomagnesemia (Low Magnesium)

Causes:

Inadequate dietary intake
Gastrointestinal losses (diarrhea, vomiting)
Renal losses (diuretics, diabetes)
Alcoholism
Certain medications (proton pump inhibitors, aminoglycosides)

Symptoms: Muscle cramps, tremors, seizures, arrhythmias, weakness

Hypermagnesemia (High Magnesium)

Causes:

Renal failure
Excessive magnesium supplementation
Magnesium-containing laxatives/antacids
Lithium therapy

Symptoms: Nausea, vomiting, hypotension, bradycardia, respiratory depression

Conversion Formulas

mmol/L to mg/dL: mg/dL = mmol/L × 2.43

mg/dL to mmol/L: mmol/L = mg/dL ÷ 2.43

g/L to g/dL: g/dL = g/L ÷ 10

Important Clinical Considerations

Clinical Utility

Corrected magnesium provides a more accurate assessment of magnesium status in patients with abnormal albumin levels, preventing misdiagnosis.

Limitations

This correction formula estimates protein-bound magnesium. Ionized magnesium measurement remains the gold standard for assessing magnesium status.

Laboratory Methods

Most labs measure total serum magnesium. Specific ion-selective electrodes are required for ionized magnesium measurement.

Cardiac Implications

Magnesium deficiency is associated with cardiac arrhythmias, hypertension, and increased cardiovascular mortality.

Therapeutic Monitoring

Essential for monitoring magnesium therapy in critically ill patients, especially those receiving IV magnesium.

Documentation

Always document both measured and corrected magnesium values in patient records for accurate clinical assessment.