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How Excessive Vitamin D Supplements Can Suppress Thyroid Function

There's something I've been talking about for years that every woman in burnout should know about because it's not mainstream yet. Even though it has a huge impact on your health to the opposite of what the mainstream is suggesting. 

Did you know that excessive vitamin D supplementation can contribute to a loss of potassium and suppress thyroid function? *Read this research article demonstrating renal potassium wasting induced by vitamin D.

[I'm talking, doses of several thousand IU taken over many months to years without adequate testing or considering how the body utilizes the supplement form of D versus how it would make it's own through sun exposure on bare skin. As well as, understanding the role it plays in the mineral system, which is most people is already favoring a high tissue calcium state of biochemistry]. 

Vitamin D can actually have an antagonizing impact on thyroid function because it can increase the absorption and retention of calcium. This can drive the calcium to rise, but the question is is the body able to utilize all the calcium? What happens in the body when tissue calcium levels rise but the right co-factors aren't on board to move it to where it should be going? 

By the way, I did a whole podcast episode about this for you HERE. Episode #40 of the A Joy To Be Me podcast (ask Alexa to play it for you). Or find it on: iTunes, iHeartRadio, Stitcher or Spotify. 

So how does excess vitamin D suppress thyroid function? 

In my post: What you need to know to assess vitamin D more thoroughly, I shared that supplements of this secosteroid-hormone-vitamin act differently than getting it straight from source (the sun). It's really good at quickly raising tissue calcium but the question is; do you really want that? What happens when the other calcium co-factors are missing -like magnesium which is also required in many steps of vitamin D metabolism when we get it through sun to skin? 

Vitamin D grabs calcium and holds on to it for dear life and you can accumulate so much calcium that it overrides your magnesium and forces it out of your body. When tissue calcium raises the bodies first response is to find magnesium to keep these two mineral in balance. This can lead to a deficiency in magnesium in proportion to calcium. 

Additionally, in it's need for more magnesium the body will suppress adrenal function in order to retain more magnesium to compensate for the high calcium. This adrenal suppression also leads to a continuous loss of sodium and potassium in the urine. This loss of these two key minerals hits the body hard the longer it goes on. 

The longer they are depleted the more the body falls into burnout and metabolic disarray. The loss of intracellular potassium increases what is more of a thyroid hormone resistance pattern. Similar to all the symptoms of hypothyroidism but with 'normal'  thyroid blood tests. Oh and then, the cells become starved for glucose and amino acids to keep the metabolism running. 

So, this excess tissue calcium elevation to loss of intracellular potassium on a hair analysis will show a very imbalanced Calcium-to-Potassium ratio, which is the ratio we use to find out about how efficiently the thyroid is functioning.

 It's time to rethink Vitamin D supplementation folks.

Here’s a common scenario I see in my practice (and in my student's client case studies), of this mineral burnout pattern I just described above. 

Above is an example of how vitamin D impacts the mineral system : just with the 4 macros: 

- It drives up calcium (shows high in the tissue level, normal calcium is 42 this client's went from 230 to 407)
- which causes the body to seek magnesium to balance (elevates the tissue level, normal magnesium is 6 this client's went from 37.8 to 67.5)
- which over time drives down potassium (low tissue potassium reading normal is 10 this client's is now a 2). 

This client took vitamin D supplements for 20 years, 3000 IU daily. Blood work did not indicate a need, the client chose on their own to supplement this way. 

I do not believe the original calcium levels were elevated SOLELY due to the vitamin D supplementation alone as there are other reason excess tissue calcium can occur. Elevated tissue calcium is very common on HTMA, with that in mind it's an already imbalanced calcium and mineral metabolism that can become so much worse with inappropriate vitamin D supplementation. I do believe it is making this client's already deranged mineral metabolism MUCH WORSE. 

*This is not unusual, I've had many clients come to me having taken a lot of supplemental D for a long time without any real reason to do so other than, they read they needed it or believed it was important. Yet they were missing CRUCIAL information and education on how to be more thorough as to not throw their biochemistry further off balance. 

Now let’s look at how it impacted the mineral ratios and what that could mean short and long term in their health.

Let’s specifically look at the Ca/K ratio : Calcium to potassium
Which in the mineral analysis world, we call the 'Thyroid Ratio'
The Optimal level of this ratio is 4.20,  this clients is 203.50

This ratio is related to thyroid function because calcium and potassium play a vital role in regulating thyroid activity.

  • The thyroid gland is one of the major glands, which regulate metabolic rate in the body. 
  • When the thyroid ratio is elevated, the efficiency of energy production in the body decreases. It is like an engine that is turning too slow, the power output declines.
  • Does not always correlate with blood thyroid tests because hair analysis is a tissue test. Often blood tests will be normal but hair analysis will indicate an impaired thyroid function. 
  • Faulty cell permeability can affect the ability of the hormones to get into the cells effectively. An elevated Ca/K ratio indicates less cell permeability 


In the short term, too much D will slow down the metabolism leading to lowered overall energy and it will blunt the effect of hormone reception at the cell wall. In the case of thyroid health, this puts one's body into more of a thyroid hormone resistance pattern Resulting in the same physical symptoms as hypothyroidism. Which is interesting considering so many thyroid groups online PUSH taking excess amounts of vitamin D. Things that make you go hmmm?

Imagine, thinking taking ONE single hormone 'vitamin' in isolation without understanding how it works in the body along with other factors was helping improve health when indeed it was not. While all along, nature could have provided it for you. 

Another example to show how vitamin D impacts the mineral system, raising the calcium which leads to seeking magnesium and drains potassium. (*Note: the sodium here is falsely elevated due to the use of a water softener at the time this client cut/collected the 2nd hair sample). 

In this case, the client took 5000 IU of supplemental vitamin D with 300 mcg of K2. NO MAGNESIUM was taken. They took that dose for 7 months. The original stored D levels tested in the spring were 28 ng/dL. *Remember, stored levels alone do not give enough information. The doctor suggested they take vitamin D, but did not give a recommended dose or guidance on how long or when to retest, OR or or how to actually get it from the SUN! 

*Note: the sodium level is falsely elevated due to client using a water softener for the shower which has an effect on the sodium level. The hair sample will end up with a build up of sodium. 

Anyway, again we can see an elevated tissue calcium and decreased tissue potassium. This slow 1 oxidizer pattern is already incredibly common today apart from the excess vitamin D supplementation. The excess D stores take a long time to come out of storage into the tissue, this client could have elevated calcium for awhile as the body works to unload the excess from out of storage. This client was also not taking any magnesium while taking this dose of D. 

Here you can see the thyroid ratio; calcium to potassium increased from 39 to 65. It's supposed to be 4.2. 

This is even someone who took some vitamin K2 with their D supplement. Usually we applaud that. I even heard a supplement specialist in the health food store educating on how you need K2 with D but yet STILL recommending high doses and no other info. 

The role of K2 does not usurp the fact that magnesium has to be available for D to work as well as how too much D will keep the demand for magnesium high. If one is not also testing tissue stores of magnesium and taking a more balanced approach they can throw themselves into a magnesium deficiency. Which by the way, also affects thyroid function (and whole system function). 

I hope these examples caused you to question the blind allegiance to high dose vitamin D supplementation we've collectively heard preached from the holistic health pulpits over the years. 

Nutrients act in a coordinated manner in the body, not solely apart from each other. I'm all about synergy and working with the whole system which is a huge reason why I'm exposing the issues excess isolated supplementation of vitamin D can be. 

I'm curious...Did you find this post helpful? Did you have any big take-aways? Are you more open to question the narrative around vitamin D supplementation? I work with people in a few ways as you can read about below. I work with clients as well as holistic health practitioners. See which of the following below could be the best fit for you if you are ready to take the info. in this post further. 


Ready to increase your energy by balancing your body's minerals? This mini program is for anyone who wants to take their health to the next level. If your health is not where you want it to be after having cleaned up your diet, detoxed your personal care products implemented an exercise routine, hand normal test results with your docter but still don't 'feel' normal -it's time to remineralize. 

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