Is it important to supplement Selenium, magnesium and potassium?

[MochasAndMusings]

Hi Folks. What do people think regarding how necessary it is to take these supplements for hypo and hashi's?

I keep reading that it is important to take selenium, magnesium and potassium to help with low thyroid function.

I was surprised about potassium. Apparently, vitamin D in excess causes low potassium levels which is common in hypothyroidism 🤔. I've not heard of this before.

I hate taking supplements as they are always large, and I struggle swallowing them, particularly the plastic type capsules. All the supplements give me an icky belly too, and I dread the dinner time vitamin and mineral routine for that reason. If I can avoid taking them, I will.

How important is it to take these three supplements? I know Vit D and B12 is important.

Also, if anyone knows of any vitamin products that do not contain cellulose, I'd be grateful. Cellulose seems to bloat me out. I think it's that whick gives me an icky belly and it seems to be in all supplements bar the Better You sprays, but these do not cover all vits and minerals.

By the way, private blood testing is not in my current budget, so I have to wing it when it comes to supplementation. My NHS doctor is very reluctant to do vitamin testing unless there's an obvious symptomatic deficiency.

Thank you, your thoughts will be gratefully received 😊.

[Buddy195 Administrator]

We certainly advise testing key thyroid vitamins (ferritin, folate, B12 and vit D) prior to considering supplementing.

I personally take magnesium daily, early evening, as it helps me relax and sleep better. I take magnesium glycinate as I find this gentle on the stomach, but others may forum members prefer other types. This post discusses different types:healthunlocked.com/thyroidu...

I don’t supplement potassium, but do eat bananas and legumes regularly to ensure I have sufficient in my diet.

A word of caution to those choosing to supplement with selenium; doses of above 400ug per day have been shown to be toxic. In the past, I have supplemented with 200ug when diagnosed with active Thyroid Eye Disease (as studies have shown it can help mild/ moderate cases if taken for 6 months). I then reduced to 100ug. Selenium supplementation did reduce my antibody levels (however, they still remain over range). As Brazils can contain 50-90ug selenium each (depending on selenium content of soil where grown) it’s not advisable to take a selenium supplement AND eat a couple of Brazils a day.

[MochasAndMusings in reply to Buddy195]

Thank you, very helpful.

[Regenallotment Ambassador]

we read so much about these don’t we. My advice (having got this particular T shirt) is this.

Don’t wing it.

Don’t spend £25 per tub on supplements you don’t need. You will just do very expensive wee.

Save £25 a month for 4 months instead and get the most comprehensive test you can afford.

OR convince a GP to run the tests for you as you would like to try these supplements but are ‘worried about toxicity’ (magic words in speech marks) I did this and NHS GP tested everything twice 3 months apart. I was over range for selenium. Under for zinc, about right for everything else.

[MochasAndMusings in reply to Regenallotment]

Thanks. So, you only take zinc now, I presume? I need vit D for menopausal set osteoporosis. Other than that, I'm not sure. I have a lot of fatigue on a regular basis, even when my ndt is at optimum. Meaning levels of optimum, and I can't tolerate higher doses. Vits/mind don't seem to make any difference there.

[Regenallotment Ambassador in reply to MochasAndMusings]

I take D3 with K2 drops daily 4000iu all year round, zinc, lutein (recommended by optician) Magnesium Biglycinate B complex and heme iron. (Not in that order and not all daily).

[greygoose]

It's important to take what you need. And to know what you need you need to get tested.

That said, there's no point in testing magnesium because the results are unreliable due to the way the body uses magnesium. And most people are deficient in magnesium due to soils being depleted, whether they're hypo or not. So, if your kidneys are in good shape, just take some. It's water soluble, so excess is excreted. And you can get that in spray form.

Taking B12 is also going to lower potassium. But that is one of the tests that doctors do routinely (and then ignore!) along with sodium. So, take a look at your last blood test results and it's probably there.

Selenium is something people seem to take without prior testing because it's necessary for conversion. But it has to be the right form of selenium - and I can't remember what that is - helvella why can't I open your blog?

[helvella in reply to greygoose]

Sorry, greygoose, I have no idea.

It works for me so the issue doesn't appear to be that the page doesn't exist, or something that obvious. Let me know what errors/warnings you see.

helvella - Selenium Document

A few notes about selenium.

Direct link to PDF:

📄 dropbox.com/s/2h3cgnuviyjto...

Last updated 10/02/2025

Link to blog:

helvella.blogspot.com/p/hel...

[greygoose in reply to helvella]

It say I don't have an account. And yet I've opened it before from that link, so I much have and account, mustn't I? lol

[helvella in reply to greygoose]

Should be no need for an account. I'll look into it later.

[greygoose in reply to helvella]

Thank you.

[MochasAndMusings in reply to greygoose]

I only get B12 tested if I plead, and as they say there's no issue, they say there's no point. My practice serves only on symptoms only. Getting tests done is like climbing Everest in flip flops. The Selenium is Selenomethionine. I've bought 200ug, but this seems to be too high. I have tried to split the capsule and half it. Not easy and tastes disgusting 😄.

[greygoose in reply to MochasAndMusings]

I don't think I mentioned testing B12, did I? I just explained about testing the three minerals you mentioned.

If you can't split the selenium capsules just take one every other day.

[humanbean]

I was surprised about potassium. Apparently, vitamin D in excess causes low potassium levels which is common in hypothyroidism

I sometimes take potassium - I got it tested [by the NHS] some years ago and, for reasons unknown, my level matched the bottom of the range. I can't afford to test it so from time to time I take a small dose supplement. If/when my levels are low I get severe cramp, and it can take hours to go away, and the pain it causes doesn't always dissipate quickly.

This article and the attached comments are interesting :

drmalcolmkendrick.org/2013/...

.

I didn't know about low vitamin D causing low potassium, I'll look into that. But I had read about low B12 and low potassium causing problems. Suppose you have low vitamin B12. B12 and potassium are required in the making of new red blood cells (RBCs). So, you start taking B12. And suddenly your body goes into a frenzy of making red blood cells because the low B12 prevented you from making enough, but now you are supplementing the body can "catch up".

But B12 isn't the only thing required for making RBCs - you need potassium too. So, if your body goes mad making RBCs you can run low in potassium. And that can make people feel very unwell. Eventually, your RBC levels will normalise and your need for more potassium than usual will go away.

Iron is also required for making haemoglobin which is found in RBCs. So if iron is low then it will reduce your body's ability to make haemoglobin for that reason too. I'm sure that the list of nutrients required for making RBCs and haemoglobin is very long, but I've never seen the "shopping list". I just know that B12, folate, iron, potassium and magnesium will be on it. So will calcium, but people rarely seem to run out of that, and too much of it ends up lining the arteries, which is not good.

You might find these links of interest :

life-enthusiast.com/article...

blog.metagenics.com/wp-cont...

And this has lots of links that might be useful :

lpi.oregonstate.edu/mic/nut...

[MochasAndMusings in reply to humanbean]

Thank you. It is too much vitamin D that causes potassium deficiency apparently. I have been prescribed a calcium and and D supplement by a Rheumatologist for my osteoporosis,but have since read several articles saying calcium should not be supplemented due to what you said, and isn't necessary other than in dietary form for the treatment of osteoporosis.

[SlowDragon Administrator in reply to MochasAndMusings]

A banana a day should be enough potassium……or even half a banana if you have someone to share it with for breakfast

[MochasAndMusings in reply to SlowDragon]

Sounds better at dinner time with whipped cream and a drizzle of chocolate as a 'banana split' 😋😋😆. Thanks!

[SlowDragon Administrator in reply to MochasAndMusings]

Not if you’re on dairy free diet……

But dairy free custard by Oatly would be delicious with banana!

And a few dairy free chocolate drops on top

I might have that tonight

[MochasAndMusings in reply to SlowDragon]

No dairy free for me thank goodness. Love the stuff 😄

[RedApple in reply to SlowDragon]

Potatoes and avocados are actually a higher source of potassium than bananas, and both contain less natural sugars than bananas.

[humanbean in reply to MochasAndMusings]

I have been prescribed a calcium and and D supplement by a Rheumatologist for my osteoporosis

Just out of curiosity, did your doctor test your calcium level before prescribing a supplement containing it?

From what I've read on the forum most doctors dish out supplements containing calcium without much thought behind it, and it never seems to occur to them that the patient might have plenty of it already.

Low vitamin D can make it hard or impossible for the body to absorb calcium from one's diet. So optimising vitamin D should increase calcium level from diet.

Personally, I love dairy, and I drink a lot of milk, cheese, sometimes ice cream, and my calcium has almost always been top of the range, or close to it, when tested. So no doctor would persuade me I need to supplement it.

However I do supplement vitamin D.

[RedApple in reply to humanbean]

'most doctors dish out supplements containing calcium without much thought behind it, '

Certainly my experience. Supplements containing calcium are the last thing to be taking if, for example, you happen to have undiagnosed or borderline Hypercalcemia or Hyperparathyroidism.

[MochasAndMusings in reply to humanbean]

I think they just prescribe Calci-chew (D/Calcium) as a routine for Osteoporosis. I started to take D3 without the calcium a while back.

[humanbean in reply to MochasAndMusings]

I think that prescribing anything as routine for people is bad medicine and poor policy, to be honest.

[MochasAndMusings in reply to humanbean]

That's the current state of affairs with the NHS these days unfortunately 🙄 😒

[RedApple in reply to humanbean]

Thanks for the reminder about potassium and cramps HB, I'd completely forgotten that. I need to re-read the Kendrick potassium article too!