yes, high d3 intakes over long time need to be carefully balanced with minerals or there can be consequences - which i've learned by experience.
hypercalcemia and hypomagnesemia are both potential consequences of straight D3 supplementation. (i can't find research on the hypomagnesemia side of things but i have experienced it and learned about it from a pharmacist). also, if you have low zinc status and correct it, your vitamin D3 dose response could improve (again i can't find a study - yet - but this is my personal experience).
high vit D intake without magnesium supplementation actually drove down my magnesium status until i developed frightening symptoms. that pharmacist turned me on to magnesium and i felt he quite literally saved my life. at that stage i hadn't had tests, but after this experience i started reading more and getting lab work done.
as for the kind of test (from mgwater.com):
A.1. Limitations of Serum or Plasma Magnesium Levels
A.1.1. What is the Normal Range?
Serum magnesium levels are normally maintained within a very narrow range, with a coefficient of variation of only 10% to 20%, unless there is a profound deficiency... Thus, the serum or plasma magnesium level is not a reliable index of magnesium deficiency.
About the Misdiagnosis of Magnesium Deficiency http://www.jacn.org/cgi/content/full/23/6/730S
•Patients with symptoms that can be part of the Mg deficiency syndrome should have their Mg serum values determined.
•In patients with Mg serum values lower than 0.9 mmol/l Mg, magnesium supplementation is recommended; for patients with values lower than 0.8 mmol/l, starting Mg supplementation is necessary. We recommend that a mMg serum value of 0.9 mmol/l Mg be considered as the lower reference limit, in evaluating symptoms or diseases suspected as being associated with Mg deficiency. In this case, Mg has to be used as a first choice therapy. When symptoms of the MDS are found, patients with serum values of less than 0.8 mmol/l Mg, or better 0.9 mmol/l Mg, ought not be erroneously declared normomagnesemic.
•When Mg substitution is started, the minimum dose to be applied is 600 mg Mg per day.
•The therapy should proceed for more than one month, and then continue with a dose that holds the serum value not lower than 0.9 mmol/l Mg.
so i'd assert that the serum magnesium test is useful if you have results below 0.91 mmol/L. i have had serum magnesium tested at two labs and one (mcmaster) says the range is 0.60-1.10 (my result was 0.88 ), and at a later date, a different local lab's range was 0.70-1.00 (i had read the 0.90 info above and by this date had obtained a level of 0.94). note that both those results count as 'normal' in the lab's and in my doctors' eyes.
, what were those levels if i may ask? the normal range is so bogus it should be illegal to make decisions about patient health based on whether or not they are under that curve.
i also failed to supplement zinc early in my learning curve. eventually i asked my doctor for a test and came back at 8.6 umol/L. healthy control zinc levels sit in the high teens. i corrected the deficiency and at next D3 testing my absorption had skyrocketed to 271 nmol/L. patients with levels over 250 nmol/L have increased risk of hypercalcemia.
you're right about the docs, tmrox, they might not know about nutrition, but at least some of them are receptive to the science once you show it to them.
my doctor has always been very helpful with my nutrition testing ideas, i began by presenting lots of peer reviewed literature, and at this stage my doc has taken things i've been investigating, and how i'm dealing with them, and made related recommendations to other patients.
also, TIMS member Mirry took the info i posted for her to her specialist (this man - http://www.cnsnevada.com/germin.html
) and apparently he is now investigating his MS patients for nutrient levels and making sure their status is optimized. i am looking forward to hearing more news on that!