Magnesium
Essential mineral for over 300 enzyme reactions, muscles, and nerves
Also known as
Definition
Magnesium is the fourth most abundant mineral in the body and a cofactor for more than 300 enzymatic reactions. It regulates muscle contraction and relaxation, nerve impulses, blood pressure, blood glucose, and protein synthesis. Only ~1% of the body's magnesium circulates in the blood, making the serum level an unreliable marker of total status. Magnesium deficiency is widespread and frequently subclinical.
| Parameter | Value |
|---|---|
| Unit | mmol/l (mg/dl) |
| Reference Range | 0.75–1.05 mmol/l (1.8–2.55 mg/dl) |
| Optimal Range (lab2go) | 0.85–1.00 mmol/l (lab2go Optimum Zone; serum Mg unreliably reflects intracellular content) |
Conversion: 1 mmol/l = 2.43 mg/dl. US labs use mg/dl (normal value 1.7–2.3 mg/dl).
↓ What a low value means
Hypomagnesemia (< 0.75 mmol/l) occurs with inadequate intake, chronic alcoholism, diabetes, kidney disease, diuretic use, or malabsorption. Symptoms: muscle cramps, cardiac arrhythmias, headaches, sleep disturbances, increased insulin resistance and blood pressure.
↑ What a high value means
Hypermagnesemia (> 1.1 mmol/l) is rare and usually iatrogenic (IV magnesium therapy, kidney insufficiency with reduced excretion). Symptoms: nausea, muscle weakness, cardiac arrhythmias; in severe cases, respiratory depression.
✓ How to optimize this marker
Dietary sources: pumpkin seeds, almonds, spinach, legumes, whole grains, dark chocolate. Supplementation: 200–400 mg/day elemental magnesium; glycinate or malate for better tolerability and bioavailability. Magnesium oxide has the poorest absorption. Timing: evenings for improved sleep.
When to test
With muscle cramps, cardiac arrhythmias, sleep disturbances, diabetes, diuretic therapy, or high athletic load. Magnesium loading test or erythrocyte magnesium is more sensitive than serum Mg for intracellular assessment.
Frequently asked questions
Why is the magnesium blood test often unreliable? +
Only ~1% of the body's magnesium is in the serum. The body maintains serum levels by releasing magnesium from bones and muscles even when total stores are depleted. A normal serum Mg value does not rule out intracellular magnesium deficiency. Erythrocyte magnesium is more sensitive.
Which form of magnesium is best for sleep? +
Magnesium glycinate combines magnesium with glycine, which itself has sleep-promoting and anxiolytic properties. Magnesium threonate is said to cross the blood-brain barrier particularly well. Magnesium citrate is well bioavailable and cost-effective. Magnesium oxide is the least well absorbed.
How much magnesium do I need daily? +
US recommended daily allowances are 310–320 mg/day for women and 400–420 mg/day for men. Athletes, pregnant women, and people with diabetes may have higher needs. Many people no longer reach the reference value through diet alone, as modern agricultural soils are increasingly magnesium-depleted.
Can magnesium lower blood pressure? +
Meta-analyses show that magnesium supplementation can lower systolic blood pressure by ~2–4 mmHg, especially in people with magnesium deficiency or elevated blood pressure. The effect is modest with adequate baseline intake but clinically relevant in combination with other measures.
Sources
Last Reviewed: May 28, 2026 · sina
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.