magnesium
Meaning of magnesium: Leafy greens, nuts, seeds, beans and whole grains supply it, and the kidneys decide how much of it stays.
Definition of magnesium
Magnesium is a mineral the body needs in comparatively large amounts. It takes part in the chemical reactions that release energy, build protein and copy DNA, and it helps nerves fire, muscles contract and then relax, and the heart hold a steady rhythm. Most of the body's magnesium is locked into bone, and nearly all the rest sits inside cells.
What does magnesium actually do?
Magnesium works mostly as a partner to enzymes. Hundreds of them will not function without it, including the ones that handle the cell's energy currency, since the usable form of that molecule is bound to magnesium. It also sits at the mouth of certain channels in nerve and muscle membranes, where it damps down excitability. That single role explains a lot of what goes wrong at both extremes: too little and nerve and muscle fire too readily, too much and they fire too little. In bone, magnesium sits in the mineral lattice alongside calcium and phosphate, contributing to structure and acting as a reservoir.
How is the level controlled?
Intake comes from food and, in smaller measure, from drinking water. Absorption happens along the small intestine and rises when intake is low. The kidney does the fine tuning, reclaiming most of the magnesium it filters and letting the surplus go in urine. Because the kidney is the main exit, magnesium accumulates when kidney function is poor, and it falls when the gut loses fluid over a long period through diarrhea or when medications increase urinary losses.
What happens when the level shifts?
| Too low | Too high | |
|---|---|---|
| Nerve and muscle | Cramps, twitching, tremor, weakness | Weakness, reduced reflexes, drowsiness |
| Heart | Irregular rhythm | Slowed conduction, low blood pressure |
| Other minerals | Potassium and calcium often fall too | Usually unchanged |
| Common setting | Prolonged diarrhea, alcohol use, certain drugs | Reduced kidney function, magnesium containing preparations |
One caveat runs through all of it. A blood test measures only the magnesium in serum, which is a small fraction of the total, so a normal result does not prove that stores inside cells and bone are adequate. That gap is part of why depletion is easy to miss. A concentrated form, magnesium sulfate, is given by injection in a few specific situations.
Also known as
Used in a sentence
The laboratory panel included a magnesium level as part of the metabolic evaluation.
Good to know
Low magnesium often occurs alongside low potassium or low calcium, and correcting those minerals is difficult while magnesium stays depleted, so evaluation of one commonly prompts checking the others.
Word origin
Where “magnesium” comes from
Named after Magnesia, a district of ancient Thessaly in Greece, whose mineral deposits gave the element its name.