09/04/2026
If you have had magnesium tested and been told your level is normal, that result is weaker than it sounds. Only about 1% of the body's magnesium is in the blood — the rest sits in bone and inside cells — so serum can read normal while stores are low.
Roughly half the population takes in less than the estimated average requirement. The RDA is 400 to 420 mg a day for adult men and 310 to 320 mg for adult women, and most people are closer to the floor than they think.
The form matters more than the milligram count on the front of the bottle. Magnesium oxide is cheap and poorly absorbed — single-digit percentages in some studies — so a big number on an oxide label is not the number that reaches you. Glycinate and citrate absorb considerably better. Typical supplemental doses run 200 to 400 mg of elemental magnesium.
Which form to choose for what, and why the standard blood test misleads:
Magnesium is involved in hundreds of enzyme reactions and roughly half of adults fall short. The differences between forms are large — here is which to choose for what.
