Thyroid UK
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Magnesium blood tests

I took the bull be the horns after a recent Endo visit didn't produce the requested T3 result

[What is it with Labs?]

I went private, as I wanted a Reverse T3 figure to go with it to get a ratio for evaluation on T4 conversion. I know NHS don't do RT3 so I plumped for those two & some mineral tests [Selenium+Zinc High! Oops] and also RBC Magnesium- said to be the best evaluation test for Low Mag .

What comes back? Whole blood Mag- & still low in the lower quartile, but not the RBC requested!

I'm trying to get this resolved but it shows that even going private hits the 'Labs' barrier.

Still awaiting the Iodine and RT3 results, too..

This article is good and refernces the tests by Song Y. [Ref 17] that support their overview.

Bear in mind that Hypothyroid symptoms and Low Mag. run almost parallel & can of course co-exist readily.

This feels very much like a re-run of UAT saga where tests and limits thereof are either ignored or brushed aside by these experts at their desks...

If you're struggling to get heard on UAT/CFS - ask for RBC Magnesium test, instead of the hard to do extra T3 Thyroid tests- maybe that will show up a deficiency worth chasing through.

I hope to progress this further.. seeing a friendlier than average Endo next month, to discuss [I wonder?]

19 Replies

Thank you for posting this, In June I had a magnesium RBC test done, but I can see from the ranges given in your article that it was probably the serum test not the RBC, so I will now go back and query it.


There are 2 tests can be done. One is take up in the cells but usually norm al blood test for it. It does work as I have a magnesium problem and test proves reliable for me.



So Jackie you mean the normal blood test for magnesium is also a good indicator of levels? I thought the red blood cell one was the best. I phoned the lab just now and they had only done the normal one not the rbc, which is annoying as it was done through a doctor and I had requested the rbc. Also the cost was somewhat different so I've learned a lesson there!


HI T here are 2 specific tests for magnesium. It is important it stays in its tiny range as an electrolyte ( heart and kidneys). The normal cheap test is just for magnesium in the blood. The other one ( more exact) is the magnesium in the cells, not normally done.. cost.



Framboise..Exactly what happened to me! Still awaiting resolution..


Jackie- thanks for your experience but there are 3 tests listed in the article with specific ranges [end of p3 and later]. Plasma, whole blood and RBC.

There's also a 24 excretion rate test.

If a test works for you then great but it's hardly right that paid for tests are replaced with another due to difficulties in the lab or whatever.

The RBC test itself is not the 'be all' of diagnosis- just that all comments seem to point to it's usefulness in deficient states.

What worries me is the power than people in white lab coats seem to hold over the medical profession,Tax money via NHS high handed managers -and even expensive private access now!

Costs here are alredy about 3 times the cost in the US- probably using the same equipment..

Finally- if you look at the ranges given in the article they each show an increasing proportion of Mag in serum or cell as it gets nearer the carrier cell of importance- the RBC. It's no surprise that where the focus is for deficiency, which can be serious, and seems to be totally neglected by most medics.

Then again- they are paid for diagnosing high BP which can readily be caused by low Magnesium.

Ahem- best not ruin a good thing!


I had magnesium tested and it was within range. But I used a magnesium spray and my arms were tingling after the first use that suggests to me my levels were low! :o Confusing eh?


My Mag last year was 0.71 [0.7-1.0] after supplementing some time as I thought I could be low.[No comment form Doc or Lab!]

This year it was 0.75 which ,though better, is lower than the minimum stated in the article of 0.8 as acceptably 'Not Low'.

0.4 is 'coma' territory -so I fail to see why low levels are ignored by all and sundry.

Well. I know why - as Docs do minimum nutrition training and are used to a pill for every ill these days.

I'm just having to experiment on myself now as I don't want synthetic hormones if at all possible.

I'm also testing out Lugols on the skin and that goes readily in about 8 hours ,not 24 as with optimum Iodine stores.

This is only possible to do with regular testing of Thyroid status, though.


Your magnesium was only just within range then! My result was 0.89 (0.7-1.00) so why the magnesium spray might have "worked" for me (as in made my skin tingle after using it) is something I can't understand. What are Lugols?


With many of these supps the level you see in serum is not always totally the picture and you may still have needed more. Without looking into it further it's hard to say, really. If you have sympmtoms and the relieve then that's a good test. just like normal approach to any medicine.

Mag is not too good to overdo- like all good things, though.


Thanks. I have many other symptoms but I've considered them to be hypothyroid ones.

Weakness (especially in legs of late) - have attributed that to the Hashimoto's

Fatigue (especially worse since being on the thyroxine) - attributed that to the thyroid hormone levels

Loss of appetite - attributed that to the Hashimoto's

Apathy - thought it was the Hashimoto's

Insomnia - thought it was because I'm taking thyroxine at night/Hashimotos

Tingling (legs only) - have attributed that to the Hashimoto's

Nausea - Only upon waking after a nap

Just spoke to a friend who knows a fair bit about magnesium levels - apparently 99% of magnesium is in the tissues. I don't see many articles on this so I can't be sure of this.


Yeah- I know how you feel.

I sent an email to my private clinic about the lab they use doing the wrong test and said in it that there's no reason one can't be Sub Clinical HypoT and low in Mag- the symptoms are so similar.

TBH the one thing you haven't listed is muscle cramps which have woken me up shouting in pain, at night.

Since I upped the Mag to a decent dose they have eased a lot.

Mag. is important to make muscles relax , just as Calcium is used to contract them. They work together and are often taken that way to be safe long term.

Potassium is also important in muscle health esp.the heart!


Ah, oops, I did have muscle cramps in my calves a few days ago. I think I wrote a post about that. My mum suggested I try ginger ale because she gets cramps herself. They have actually eased off since I drank that. Whether ginger is therapeutic or not I don't really know so I'm reserving judgement on the ginger ale doing anything. I've read that ginger ale mostly has a placebo effect on things like that but who knows? :)

I had a bad lot of cramps four months ago. They were so bad I couldn't lift my leg to use the stairs or put my feet up.


If you can get tested readily enough could be worth taking more Mag. Citrate is easily absorbed. Ask you GP, if friendly on self help. Not many are that supportive though- in my exp,


Ok, thanks. I have an appointment with my GP on Tuesday but I might get the appointment moved to Monday if I call in early enough. :)


Good luck - let me know how it goes! It's possible the lab had an earlier mistake which may show up on retesting,

Also, if like me, you may be sensitive to co-factors to your HypoT condition running at sub optimal [& in my case, NO] treatment.

PS: Lugols [my version] is 12% Potassium Iodide/Iodine solution used in water or painted on skin to up Iodine levels. Skin takeup indicates level of any deficiency -so I use that method.

Iodine is 90% of T4 but NOT to be messed with, without tests and some supervision.

I am currently not on any thyroid meds, either.

It has got a bogey-man name, though-probably as it could cure many things, used intelligently but forgotten these days.

It's most renowned use is to be issued in Radiation scenarios where it's used to saturate the thyroid to stop radioactive iodine being taken up.


Thanks. :) I'm hoping to get some other nutrient levels checked as I have been on this PPI called Omeprazole (I also take apple cider vinegar to help with this, too) and seeing as the PPI can affect levels of iron and other nutrients I thought it would be wise to get it checked out. I think having an autoimmune disease predisposes me to develop nutritional deficiencies as well.

Shame you're not on any thyroid medication. :(

I think I've heard of the iodine thing before. As long as it's affordable I'll look at it, so thank you.

This gluten challenge is getting harder - no wonder they call it a challenge! In a way I'd rather be done with it due to what it's putting me through and just go completely gluten free but on the other hand if I stop now the antibodies they need to find for the Coeliac won't be found! What a dilemma!


There's a new test for Coeliac that can assess the amount you're dealing with over a few months. It's hard to get a firm diagnosis if borderline, I think though. If you try Gluten free for a while you well may feel better as a test!

I had it done and was clear.

On the iodine- I'm just evaluating short term usage. It's interesting to see if the body takes it up through the skin. I don't fancy taking it in water much. [Nor do many others]

It willl interfere with Thyroid meds too.

I've been on Omaprazole and though it can help acidosis I couldn't keep at it . It can cause probs with absorbing nutrients as stomach acid is vital in this. I found the H2 antagonist med Ranitidine much better when suffering reflux.

I tried Levo but it made me feel ill even on upped dose.

I would give T3 [or T3+T4] a try if needed but I still suspect I may have secondary low thyroid action due to past head injury.

If rare, the Drs. never seem to think it may apply for some reason... Hope ,I suppose.

Not much help to the sufferer, though!


Glad to say I've been on NHS T3 for 2 years now.

Not from an Endo, who are all dead against it due to T4 loyalty.



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