Magnesium: the pathway in the body

This page shows the biochemical pathway behind the laboratory value Magnesium: which stations follow one another, which enzymes carry out each step and which cofactors they use. Every statement has a source. The page describes general textbook knowledge and says nothing about any individual person.

In brief

Magnesium is a mineral that exists in the body as a doubly charged ion, mostly in bone and inside cells. It forms the active energy carrier together with ATP and acts as a brake in the NMDA receptor.

The pathway step by step

1. Magnesium in food → Small intestine Claudin-2, -7, -12 In the small intestine, magnesium passes passively between the gut cells. The passages for this are formed by proteins of the claudin family (claudin-2, -7 and -12). Source 1, 3
2. Small intestine → Large intestine In the large intestine, the channels TRPM6 and TRPM7 move magnesium into the gut cell. On the blood side, the transporter CNNM4 releases it again, probably in exchange for sodium. Source 1
3. Large intestine → Magnesium in the blood TRPM6/7, CNNM4 Only a small share of the body’s magnesium is in the blood. Most of it is in the bones, and a further share in muscles and other tissues. Source 1
4. Magnesium in the blood → Filtration in kidneys The kidneys filter magnesium from the blood. By far the largest part of it is then recovered along the renal tubules. Source 1, 2
5. Filtration in kidneys → Reabsorption Claudin-16/-19, TRPM6 The loop of Henle recovers most of it, between the cells through pores made of claudin-16 and -19. Fine-tuning is done by the distal tubule with the channels TRPM6 and TRPM7. Source 1, 2
6. Magnesium in the cell → Mg-ATP ATP, the cell’s energy carrier, forms the Mg-ATP complex with magnesium. It is regarded as the biologically active form; through it, magnesium takes part in several hundred enzyme reactions. Source 1, 4
7. Glucose → Glucose-6-phosphate Hexokinase Hexokinase transfers a phosphate group from ATP to glucose for this. It uses the Mg-ATP complex as its substrate. Source 1, 5
8. Glucose-6-phosphate → Glycolysis Glucose-6-phosphate is the entry point to glycolysis, the breakdown of sugar to release energy. Magnesium is needed for this pathway. Source 5
9. Magnesium in the cell → NMDA receptor The NMDA receptor is a calcium channel opened by the messenger glutamate. Magnesium sits in its pore and has to leave before calcium can flow in. Source 5, 4
10. NMDA receptor → Calcium influx · Glutamate When the magnesium block is released, calcium flows into the nerve cell and the signal is passed on. At this site magnesium therefore acts like a brake. Source 5

Cofactors in this pathway

• ATP — Forms the Mg-ATP complex with magnesium, the form used by enzymes such as hexokinase Source 4, 1
• Sodium — The transporter CNNM4 probably releases magnesium into the blood in the colon in exchange for sodium Source 1In the ORY catalogue as a laboratory value: Natrium (intrazellulär)
• Potassium — Its recycling in the loop of Henle builds the voltage that drives magnesium back between the cells Source 2In the ORY catalogue as a laboratory value: Kalium (intrazellulär)
• Calcium — Flows in through the NMDA receptor once magnesium has left the pore Source 5In the ORY catalogue as a laboratory value: Calcium (intrazellulär)
• Glutamate — Messenger that opens the NMDA receptor, in whose pore magnesium sits Source 5In the ORY catalogue as a laboratory value: Glutamat

What acts on this pathway

• Acid blockers — Proton pump inhibitors raise the pH in the gut. It has been described that magnesium then stays less well dissolved and the channel TRPM6 in the large intestine is less active. Source 1
• Diuretics — Loop diuretics inhibit the transporter NKCC2 in the loop of Henle; this removes the electrical gradient that drives magnesium back between the cells. Lower magnesium levels have also been described with thiazide diuretics. Source 1

Sources

1. Kröse JL, de Baaij JHF. Magnesium biology. Nephrol Dial Transplant 2024 · PubMed 38871680
2. de Baaij JHF. Magnesium reabsorption in the kidney. Am J Physiol Renal Physiol 2023 · PubMed 36633869
3. Schuchardt JP, Hahn A. Intestinal Absorption and Factors Influencing Bioavailability of Magnesium — An Update. Curr Nutr Food Sci 2017 · PubMed 29123461
4. de Baaij JH, Hoenderop JG, Bindels RJ. Magnesium in man: implications for health and disease. Physiol Rev 2015 · PubMed 25540137
5. Kirkland AE, Sarlo GL, Holton KF. The Role of Magnesium in Neurological Disorders. Nutrients 2018 · PubMed 29882776

Related pathways

• GABA, glutamate and glutamine — Natrium (intrazellulär), Kalium (intrazellulär)
• Gut fermentation and breath gases — Natrium (intrazellulär), Calcium (intrazellulär)
• Gluten antibodies — Calcium (intrazellulär), Glutamat
• HbA1c and insulin — Kalium (intrazellulär), Calcium (intrazellulär)
• Pancreatic elastase — Natrium (intrazellulär), Calcium (intrazellulär)

As of 2026-09-16. Draft written by Claude to schema v2; sources checked in PubMed; expert review pending
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