On lab work my magnesium was 2.4, top of "normal" range. should i continue to take a daily over-the-counter mag supplement? worried about toxicity?

No need to worry: 99% of magnesium in our bodies is inside our cells ; less than 1% in our blood so serum mag. Is not a good indicator of overall mag. Status. Your blood level is still normal. Magnesium toxicity is extremely rare ; generally only occurs in those with kidney failure, so unless you have kidney failure there is no need for concern. You might still even have magnesium deficiency! http://bit.Ly/1dpai09.

Dr Baker is correct: It's a fundamental but common mistake to think of the reference range as "normal". It's deliberately set so that several percent of healthy folks fall outside on either end. Low magnesium may be a common unrecognized health problem, but serum levels are a very poor reflection of the adequacy of one's supplies since magnesium is intracellular. Best wishes.