Did you know…

Less than 1% of your body’s magnesium circulates in the blood. The remaining 99% is locked inside cells, bones, and muscles. The standard serum magnesium test measures the 1%, and its reference range is calibrated on a magnesium-depleted population. A person can be profoundly magnesium-deficient at the tissue level and receive a normal serum result.

The claim, in the words of the international magnesium research network

The MaGNet network is an international consortium of magnesium researchers whose 2022 recommendation in Advances in Nutrition is the most direct statement on record about the failure of the standard test:

“Widely varying serum magnesium reference ranges render our use of this important medical tool imprecise, minimizing impacts of low magnesium status or hypomagnesemia as a marker of disease risk.”

— MaGNet Network, Advances in Nutrition, 2022

Their clinical review had earlier established, in the same field, the more fundamental point:

“An individual may be profoundly deficient in total body or intracellular Mg required for various cellular biochemical processes yet have a SMC [serum magnesium concentration] within normal range.”

— MaGNet clinical review

What the numbers actually show

In one study of hypertensive patients, 80% had magnesium depletion confirmed by a loading test even though their blood magnesium was normal or elevated. Among patients hospitalized in intensive care units, half are deficient in intracellular magnesium despite a normal serum result. A 2010 analysis found that only 10% of cases of hypomagnesaemia were detected at the physician’s request; the remaining 90% were found incidentally during routine tests. Physicians are not even looking.

The recommendation nobody has adopted

MaGNet recommends raising the minimum threshold from the usual 0.70-0.75 mmol/L to 0.85 mmol/L. No major laboratory has updated its printouts. The test that misses the tissue continues to reassure the patient at values that, on a properly calibrated scale, would already flag a functional deficit.

This entry is a companion to Right to Optimal Magnesium Status and to The Hunger We Don’t See.