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Vitamin D and Magnesium Interconnectedness

Magnesium is required to convert Vitamin D into its active form in the bloodstream.  As a result, Vitamin D supplementation (especially  high-dose) may actually cause or exacerbate magnesium deficiency.  It can be an major disruption in your quest to create a wildly-satisfied client if someone who begins using  a Vitamin D supplement suddenly starts having muscle cramps, acid reflux, constipation, or headaches!  You will also want to look for this connection in your new clients given their prior labwork and their symptom checklist.  You may find this or this interesting.

When your clients and patients seek to understand their Vitamin D level, encourage them to request an “RBC magnesium” (vs. serum magnesium) level at the same time.  As with all mineral labwork, it is best to aim for the upper third of the reference range, given the high incidence of mineral nutrient deficiencies.  Remember that RBC mineral levels better reflect ongoing nutrient levels over a 3-4 month time period (vs. typical serum levels which only reflect dietary/supplement intake for the past few days at most).

In the absence of labwork (and assuming no overt kidney disease), I recommend including magnesium supplementation when a client is using a Vitamin D supplement, especially if it’s more than 1000 IU daily of Vitamin D3 (higher levels of which most of our clients will need from October through April).

I recommend magnesium glycinate for most of my clients who need to increase their magnesium, ~300mg with food, either once or twice daily.  For constipation, magnesium citrate is a preferred form.  We have talked about magnesium at length in prior clinical tips.  RBC magnesium can be checked 4-6 months after taking a consistent supplement dose to see if it is sufficient.

Because magnesium deficiency is particularly common in your diabetic clients, this is a secondary consideration to keep in mind with these clients.  You may find this interesting.

P.S.  If you are passionate about transforming healthcare through the power of functional medicine, we encourage you to learn more about our training program here.

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Mandy Vaughan
Mandy Vaughan

What would be the best journal article you would recommend for the relationship between Magnesium and Vitamin D/the information listed above?

SAFM Team
Reply to  Mandy Vaughan

There are many articles that go into the detail of magnesium and vitamin D interdependence, here are a couple of examples that may be of interest:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9846944/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7468838/
We also encourage to explore all the articles linked in the text and in the Q&A section below.

Jodie Black
Jodie Black

Do you have take Vitamin K2 with vitamin D3 to prevent calcium build up in arteries and for better absorption of vit D3? If so, can you get enough Vit K2 from diet or is supplement necessary

SAFM Team
Reply to  Jodie Black

Great questions! You will find your answers in this post:
https://schoolafm.com/ws_clinical_know/reversing-arterial-plaque/

Melissa Lee

I read this in a paper about subclinical Mg deficiency :
over-supplementing with vitamin D may lead to magnesium deficiency via excessive calcium absorption
and hence increase the risk of arterial calcifications.

Is it because vitamin D increases calcium absorption into bone and tissue?

CAROLINA CILIBERTO
CAROLINA CILIBERTO

I understand RBC Magnesium represents the real status of Magnesium in the body vs serum Magnesium which represents more of the Magnesium that was consumed in the last few days. But what about urine Magnesium? is it representative of the sufficiency of this mineral in the body? I ask because where I live there are no laboratories ofering RBC Minerals Tests…which Marker should I use for Magnesium?

SAFM Team

Alas, there is no perfect test for magnesium status assessment. And event though RBC magnesium seems to be a more accurate measure than serum magnesium levels, we have seen plenty of examples where people with quite optimal RBC magnesium still needed more magnesium support. Urinary magnesium testing is an option but the interpretation of the results requires a thorough review of what is going on for the person as there are many underlying conditions that can affect magnesium excretion, which I encourage you to read about here:
https://www.greatplainslaboratory.com/articles-1/2016/2/22/urine-calcium-and-magnesium-in-adults-recommended-test-for-nutritional-adequacy
https://www.mayocliniclabs.com/test-catalog/Clinical+and+Interpretive/36901
Moreover, “urinary Mg declines before serum Mg and is an earlier and more reliable indicator of evolving Mg deficiency” and this has been shown here:
https://www.ncbi.nlm.nih.gov/pubmed/8538226

Joan Zietlow

Are there two different reference ranges for RBC magnesium? I mean is there a typical lab range and then a functional range? In some of the noted studies they seem to quote the average range of the study participants and not include the functional or average lab range. Can you address this please? Thank you.