π§ͺ Magnesium Unit Converter
mg/dL, mmol/L, and mEq/L for magnesium, all three at once.
Unit conversion only. Discuss your magnesium result with your clinician.
Magnesium results arrive in three different units depending on the lab and the country: mg/dL in the US, mmol/L in most of the world, mEq/L in older texts and some ICU flowsheets. Type your value in any box above and the other two fill in, with the normal range shown in all three so you can interpret immediately.
How to Use This Converter
Type your magnesium value in whichever unit your lab used. The equivalents appear in the other boxes and below.
Type the value in mg/dL, mmol/L, or mEq/L.
Read the normal range in your unit: 1.7-2.2 mg/dL, 0.70-0.91 mmol/L, or 1.40-1.81 mEq/L.
Note the band: low magnesium often coexists with low potassium and calcium, so check the full panel.
The Conversion Factors
The factors come straight from the atomic weight: 1 mg/dL equals 10 mg/L, divided by 24.305 g/mol gives 0.4114 mmol/L. Milliequivalents double the millimoles because magnesium carries two charges (Mg2+), which is the whole reason mEq/L exists: it counts charge, not just molecules. Unlike triglycerides, whose factor is an average, magnesium's factor is exact chemistry.
Landmarks: 2.0 mg/dL = 0.82 mmol/L = 1.65 mEq/L, a textbook normal. 1.2 mg/dL = 0.49 mmol/L, severely low and usually symptomatic. 3.0 mg/dL = 1.23 mmol/L, high, seen in kidney failure or excess supplementation. If your lab reports in mmol/L, the mental shortcut is "around 0.8 is normal, under 0.7 is low."
Worked Example
A lab reports magnesium 1.5 mg/dL. Convert: 1.5 x 0.4114 = 0.62 mmol/L; 1.5 x 0.8229 = 1.23 mEq/L. All three agree: low (below 1.7 / 0.70 / 1.40). A European report of 0.85 mmol/L converts to 0.85 / 0.4114 = 2.07 mg/dL: normal. The conversion is trivial arithmetic, but doing it wrong, for example reusing calcium's factor, produces confident nonsense, which is why the dedicated converter exists.
Why Magnesium Matters Clinically
Magnesium is the cofactor behind the cofactor: it powers ATP reactions, stabilizes cardiac membranes, and gates calcium channels. Low magnesium causes the refractory triad every trainee memorizes: hypokalemia that will not correct, hypocalcemia from PTH resistance, and cardiac irritability including torsades de pointes. Causes of low magnesium read like a hospital census: diuretics, proton pump inhibitors, alcohol use, diarrhea, and poor intake. High magnesium is rarer, mostly kidney failure or over-supplementation, and it sedates: loss of reflexes, hypotension, respiratory depression at very high levels.
Serum magnesium is a crude test: only about 1 percent of body magnesium is extracellular, so a "normal" level can coexist with total-body depletion, especially in chronic deficiency. The RBC magnesium test is sometimes ordered for a deeper look, though its clinical value is debated. If your level is low, the fix depends on cause: oral magnesium for mild deficiency (glycinate and citrate are better tolerated than oxide), IV for severe or symptomatic cases, and always recheck potassium and calcium alongside. Our corrected calcium calculator covers magnesium's mineral partner.
Supplements: What to Know
Dietary magnesium is safe and widely inadequate: leafy greens, nuts, seeds, legumes, and whole grains are the sources, and surveys suggest roughly half of Americans fall short. Supplements help deficiency but are not performance enhancers for the replete: the sleep and cramp claims outrun the evidence in people with normal levels. Excess oral magnesium mostly causes diarrhea (it is also the mechanism of milk of magnesia), which conveniently limits overdose in people with working kidneys. Kidney failure changes everything: impaired excretion makes accumulation dangerous, so supplement only with medical supervision in CKD.
Related Calculators
Keep exploring: try our corrected calcium and BUN creatinine ratio for the next piece of the picture.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
How do you convert magnesium mg/dL to mmol/L?
Multiply by 0.4114. Example: 2.0 mg/dL x 0.4114 = 0.82 mmol/L. For mEq/L, multiply mg/dL by 0.8229 (or double the mmol/L). This converter does all three instantly.
What is a normal magnesium level?
1.7-2.2 mg/dL, which equals 0.70-0.91 mmol/L or 1.40-1.81 mEq/L. Ranges vary slightly by lab. Only about 1% of body magnesium is in blood, so serum levels are a rough window on total stores.
Why are there three units for magnesium?
mg/dL (mass, US labs), mmol/L (molar, most of the world), and mEq/L (charge-based, older texts and some ICU flowsheets). Magnesium is divalent (Mg2+), so mEq/L is exactly double mmol/L.
What causes low magnesium?
Diuretics, proton pump inhibitors, alcohol use, chronic diarrhea, poor intake, and kidney losses. Low magnesium often travels with low potassium and low calcium, and it makes both refractory to correction until magnesium is repleted.
What are symptoms of low magnesium?
Muscle cramps, tremor, numbness, and in severe cases seizures, cardiac arrhythmias (including torsades de pointes), and refractory low potassium or calcium. Mild deficiency is often asymptomatic.
Can you have normal magnesium blood levels but still be deficient?
Yes. Only ~1% of body magnesium is extracellular, so serum levels can read normal during total-body depletion. Clinical context (diuretics, alcohol use, symptoms) matters alongside the number.
What is the best form of magnesium supplement?
For correcting deficiency, well-absorbed forms like citrate or glycinate are better tolerated than oxide, which is poorly absorbed and more laxative. Dose and form should follow the reason for supplementing; discuss with your clinician.
Can too much magnesium be harmful?
In healthy kidneys, excess oral magnesium mostly causes diarrhea, which limits absorption. In kidney failure, accumulation can cause dangerous hypermagnesemia: loss of reflexes, hypotension, respiratory depression. Supplement cautiously in CKD.
Does magnesium help with sleep?
Evidence is modest: supplementation helps sleep mainly in people who are deficient. For the magnesium-replete, effects are small. Fixing deficiency, keeping a schedule, and limiting evening light and caffeine do more.
Why does low magnesium cause low potassium?
Magnesium deficiency increases renal potassium wasting and impairs Na/K-ATPase function. The practical rule: hypokalemia that will not correct with potassium alone usually needs magnesium repletion first.