Corrected Magnesium Calculator — Albumin-Adjusted Mg
Adjust reported serum magnesium for low albumin levels — enter measured Mg and serum albumin to find the corrected (true) magnesium status, in mg/dL or mmol/L.
mg/dL
g/dL
Display unit
Low — possible hypomagnesemia
- 1
Albumin deficit from reference (4.0 g/dL)
4.0 − 2.5 = 1.5 - 2
Correction term
0.005 × 1.5 = 0.0075 - 3
Corrected magnesium (mg/dL)
1.2 + 0.0075 = 1.21
How does this calculator work?
Corrected Mg (mg/dL) = Measured Mg + 0.005 × (4.0 − Albumin g/dL). Low albumin artificially lowers total serum Mg because ~25–30% is albumin-bound. Normal corrected Mg is 1.7–2.2 mg/dL (0.70–0.91 mmol/L). Clinical reference only — confirm with a clinician.
Formula
How this is calculated
About 25–30% of serum magnesium is bound to albumin. When albumin is low (hypoalbuminemia — common in liver disease, malnutrition, or critical illness), total measured magnesium appears artificially low even though the physiologically active, unbound fraction may be normal. The correction formula adds back the estimated protein-bound fraction "missing" due to the albumin deficit: Corrected Mg = Measured Mg + 0.005 × (4.0 − Albumin), where 4.0 g/dL is the assumed normal albumin and 0.005 mg/dL is the correction factor per g/dL of albumin deviation.
For example, a patient with measured Mg of 1.2 mg/dL and albumin of 2.5 g/dL has a corrected Mg of 1.2 + 0.005 × (4.0 − 2.5) = 1.2075 mg/dL — a modest upward correction because the Mg–albumin binding fraction is relatively small compared to calcium (~40% for Ca vs ~25–30% for Mg). Normal serum magnesium ranges from 1.7 to 2.2 mg/dL (0.70–0.91 mmol/L); values below 1.7 mg/dL after correction suggest true hypomagnesemia.
The correction is an approximation using population-averaged binding constants; individual variation in pH and other electrolytes can shift the free fraction. For definitive assessment of free (ionised) magnesium, direct measurement is preferred. This tool is for clinical reference only — always confirm results with a qualified clinician.
Frequently asked questions
About 25–30% of serum magnesium is albumin-bound. When albumin is low, fewer protein-binding sites exist, so total Mg appears low even if the free (ionised) fraction is normal. The correction formula estimates the portion of Mg that appears "missing" due to the albumin deficit.
Normal total serum magnesium is typically 1.7–2.2 mg/dL (0.70–0.91 mmol/L). Values vary slightly between laboratories. After albumin correction, values below 1.7 mg/dL suggest true hypomagnesemia that may warrant investigation or supplementation.
The formula provides a clinical estimate, not a precise measurement. The bound fraction varies with pH, other electrolytes, and individual physiology. For a definitive answer, direct measurement of ionised magnesium (where available) is more accurate. Treat the corrected value as a guide, not a laboratory result.
TG we-Calculate Editorial Team. (2026). Corrected Magnesium Calculator — Albumin-Adjusted Mg [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/corrected-mg-calculator
TG we-Calculate Editorial Team. "Corrected Magnesium Calculator — Albumin-Adjusted Mg." TG we-Calculate. 2026. https://we-calculate.com/calculator/corrected-mg-calculator.
TG we-Calculate Editorial Team, "Corrected Magnesium Calculator — Albumin-Adjusted Mg," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/corrected-mg-calculator
@misc{wecalculate_corrected_mg_calculator, title = {Corrected Magnesium Calculator — Albumin-Adjusted Mg}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/corrected-mg-calculator}}, year = {2026}, note = {TG we-Calculate} }
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