The mineral your blood test won't catch
Only about 1% of the body's magnesium circulates in the blood. The rest is stored in bone and soft tissue. This is why a standard serum magnesium test can return a normal reading while your cells are running low, and why most doctors don't flag it until the deficit is severe. A 2012 review published in the Journal of the American College of Nutrition estimated that nearly half of Americans were not meeting their daily magnesium requirement. Indian data is thinner, but a 2019 cross-sectional study from AIIMS Delhi found subclinical magnesium deficiency in a significant proportion of patients presenting with non-specific fatigue and sleep complaints, conditions that had often been attributed to stress or anaemia for months before anyone checked magnesium levels.
