Magnesium !

Magnesium partners ATP in almost every energy-using reaction and steadies nerves and muscles, including the heart.

Updated 2026-11-01

Key facts

The real form of ATP in the cell is the Mg-ATP complex: all kinases (hexokinase, PFK-1) need magnesium.
More than half is in bone and nearly all the rest inside cells; serum magnesium reflects stores poorly.
Low magnesium causes hypocalcaemia (blocks PTH) and hypokalaemia (the kidney wastes potassium) that do not correct until it is replaced.
Magnesium sulphate prevents eclamptic seizures and treats polymorphic ventricular tachycardia (torsades de pointes).

Sources: green leaves (chlorophyll has magnesium at its centre), nuts, seeds, legumes, whole grains, cocoa.
Roles: cofactor of more than 300 enzymes (all that use ATP, DNA and protein synthesis), membrane stabiliser, physiological blocker of the NMDA receptor and of calcium channels.
Balance: absorbed in the small intestine and regulated by the kidney, mainly in the thick ascending limb of Henle.
Causes of deficiency: chronic diarrhoea, alcoholism, loop and thiazide diuretics, long-term proton pump inhibitors, poorly controlled diabetes, refeeding syndrome.
Hypomagnesaemia: tremor, tetany, seizures, arrhythmias (long QT, torsades).
Hypermagnesaemia (almost always kidney failure plus laxatives or an infusion): loss of tendon reflexes (first sign), hypotension, respiratory depression, cardiac arrest.
Lab: serum magnesium; urine magnesium to tell renal from gut losses.

During magnesium sulphate infusion for preeclampsia, knee reflexes, breathing and urine output are watched; the antidote is calcium gluconate.
Transketolase and thiamine pyrophosphokinase need magnesium: in Wernicke encephalopathy magnesium is corrected together with thiamine.
People with alcoholism often lack magnesium, potassium, phosphate and thiamine at the same time.

Think of the answer, then tap the question to see it.

Why do kinases need magnesium?

The true substrate is the Mg-ATP complex: magnesium neutralises phosphate charges and positions ATP in the active site.

Why does hypokalaemia not correct when magnesium is low?

Without magnesium the kidney's ROMK channels open more and potassium keeps leaking into urine.

What is the first sign of magnesium toxicity?

Loss of deep tendon reflexes, before respiratory depression and cardiac arrest.

What is magnesium sulphate used for in obstetrics?

To prevent and treat the seizures of severe preeclampsia and eclampsia.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: Magnesium in diet: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Magnesium Blood Test: MedlinePlus Medical Test (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Representative model, for educational purposes only.