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) |
Agree on your personal target range with your doctor.
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.
✓ What can influence this value
The serum magnesium value is influenced by dietary intake (e.g., pumpkin seeds, almonds, spinach, legumes, whole grains), chronic alcohol consumption, diabetes, kidney disease, diuretics, and malabsorption. Absorption depends on the specific magnesium compound. Because only about 1% of the body's magnesium circulates in the blood, the serum value reflects total status only to a limited extent. The assessment is made by the treating doctor.
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.
How do magnesium compounds differ? +
Mainly in absorption: magnesium citrate is highly bioavailable, while magnesium oxide is the least well absorbed. Magnesium glycinate combines magnesium with the amino acid glycine. Magnesium threonate is said to cross the blood-brain barrier particularly well.
Does the serum value show how much magnesium I take in? +
Only to a limited extent. Because only about 1% of the body's magnesium circulates in the blood and the body maintains serum levels from bones and muscles, the value does not directly reflect intake. Athletes, pregnant women, and people with diabetes may have higher needs. Whether and how much magnesium is taken is decided by your doctor.
Can magnesium lower blood pressure? +
Meta-analyses show that magnesium supplementation can slightly lower systolic blood pressure, especially in people with magnesium deficiency or elevated blood pressure. With adequate baseline intake the effect is small. Whether and how treatment is given is decided by your doctor.
Magnesium
Sources
Last updated: May 28, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.