Low Vitamin D and thyroid hormone utilization c... - Thyroid UK

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Low Vitamin D and thyroid hormone utilization connection?

ejg711 profile image
19 Replies

I recently read this statement on the STTM blog.

"The one thing researchers do know is “thyroid treatment isn’t optimal–and may not work–if you do not have adequate vitamin D for the crucial final metabolic step, which takes place at the site where thyroid hormone actually works. This happens inside the nucleus of the cell. Vitamin D needs to be present at sufficient levels in the cell in order for the thyroid hormone to actually affect that cell. That is why vitamin D is so crucial.”

Can anyone with knowledge or experience confirm this? I've been struggling with hypo symptoms for about four years. I gained 50 pounds last year alone, despite watching my diet and working out 3-4 times per week. I've been on various doses and combinations of t3 and t4. Ranging from 35mcgs of t3 moving up to 125mcgs, and 125mcgs of t4 only to a combination of 180 mcgs of t4 and 25 mcgs of t3. But throughout this whole ordeal, I've struggled with low vitamin D. It's been as low as 18, and as high as 27, with a reference range of 30-100 NG/ML. Could it be that simple? Also, I recently had test for TPO antibodies, and it came back 12IU/ML, with a reference range of 0-30. At what point is one considered to have Hashimotos? Thanks.

19 Replies
bantam12 profile image

Not everybody needs high vitd, I for one always have low levels and that's where my body likes it, I'm not able to take any form of vitd supplement and any attempt to raise it makes me very unwell.

Molly139 profile image
Molly139 in reply to bantam12

Hi bantam 12, could you let me know how vit D makes you feel unwell? I started taking 25mcg on Friday on the advice from my GP and I feel a bit off

bantam12 profile image
bantam12 in reply to Molly139

All supplements make me totally yuck, nausea, headache and so on, long time since I've tried Vitd but I'm fine with my levels being low, that's where they want to be 🤷‍♀️

Molly139 profile image
Molly139 in reply to bantam12

Thank you bantam12. I seem to be the same, I felt rubbish after taking magnesium and I’ve just started vitamin D, GP‘s advice as I’m low, Only started on Friday 25mcg daily, I’m not sure if it was the tablets but 20 minutes after I felt really strange

bantam12 profile image
bantam12 in reply to Molly139

Maybe try the Better You spray, I could tolerate that for slightly longer than any tablets but still had to give up. Perhaps it's your body telling you it's happy with your levels where they are, have you had your calcium checked ?

My Vitd level is usually around 12 in the winter and at most 30 in the summer and I don't try to increase them.

SlowDragon profile image

Many/most need optimal vitamin D, folate, ferritin and B12

Essential to retest these regularly

Important to test BOTH TPO and TG antibodies


20% of Hashimoto's patients never have raised antibodies


Vitamin D deficiency extremely common with Hashimoto’s


Vitamin D deficiency is frequent in Hashimoto's thyroiditis and treatment of patients with this condition with Vitamin D may slow down the course of development of hypothyroidism and also decrease cardiovascular risks in these patients. Vitamin D measurement and replacement may be critical in these patients.


Evidence of a link between increased level of antithyroid antibodies in hypothyroid patients with HT and 25OHD3 deficiency may suggest that this group is particularly prone to the vitamin D deficiency and can benefit from its alignment.

For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also EXTREMELY important to test vitamin D, folate, ferritin and B12

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .

Last dose of Levothyroxine 24 hours prior to blood test. (taking delayed dose immediately after blood draw).

This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)

If/when also on T3, make sure to take last third or half of daily dose 8-12 hours prior to test, even if this means adjusting time or splitting of dose day before test

Is this how you do your tests?

Assuming you are not in the UK?

Low vitamin D and low B vitamins may be linked as explained here


In YouTube video...vitamin D at 40ng/ml (USA units) is equal to 100nmol (UK units)

Dr Gominak


ejg711 profile image
ejg711 in reply to SlowDragon

Yes, I'm in the US. Folate was low, b12 was high and ferritin was over range, possible due to inflammation. Here are some recent test results. B121,523 pg/mL

211 - 946 pg/mL

RBC Folate665 ng/mL

>=366 ng/mL,

Folate7.0 ng/mL

7.3 - 26.1 ng/mL

Vitamin Total 25 Hydroxy27 ng/mL

21 - 70 ng/mL

Thyroglobulin Antibody <1.0 IU/mL 0.0 - 0.9

Iron and TIBC

Iron Bind.Cap.(TIBC) 329 ug/dL 250 - 450

UIBC 227 ug/dL 111 - 343

Iron, Serum 102 ug/dL 38 - 169

Iron Saturation 31 % 15 - 55

Ferritin, Serum 479 High ng/mL 30 - 400

Transferrin 248 mg/dL 200 - 370

I was on 180mcg of t4 and 25 mcg of t3. last doses were 24 and 12 hours before blood draw,

Thyroid Panel With TSH

TSH 0.013 Low uIU/mL 0.450 - 4.500

Thyroxine (T4) 7.6 ug/dL 4.5 - 12.0

T3 Uptake 28 % 24 - 39 01

Free Thyroxine Index 2.1 1.2 - 4.9

Thyroxine (T4) Free, Direct, S

T4,Free(Direct) 1.49 ng/dL 0.82 - 1.77

Reverse T3, Serum A 9.7 ng/dL 9.2 - 24.1

SlowDragon profile image
SlowDragonAdministrator in reply to ejg711

So how much vitamin D have you been supplementing?

Are you supplementing a vitamin B complex to improve low folate

TG antibodies antibodies are high.

So suggests Hashimoto’s


ejg711 profile image
ejg711 in reply to SlowDragon

I had been supplenting with 10000 IU Vitamin D once per week, and I just started a B complex.

SlowDragon profile image
SlowDragonAdministrator in reply to ejg711

So that’s only 1428iu per day...even guidelines recommend 1600iu per day for 6 months

With Hashimoto’s we frequently need higher dose than average

improving vitamin D to around 40ng/ml



Once you Improve level, very likely you will need on going maintenance dose to keep it there.

Test twice yearly

Vitamin D mouth spray by Better You is very effective as it avoids poor gut function. There’s a version made that also contains vitamin K2 Mk7

It’s trial and error what dose we need, with hashimoto’s we frequently need higher dose than average


Also read up on importance of magnesium and vitamin K2 Mk7 supplements when taking vitamins





Vitamin K2 mk7



jimh111 profile image

Vitamin D deficiency is common in hypothyroidism and it can cause its own symptoms including tiredness.

If vitamin D deficiency affected thyroid hormone action it would apply to action in the pituitary and the negative feedback would fail leading to extraordinary high TSH levels. We never see this.

Vivb56 profile image

I had a long chat with my GP after the usual FT4 and TSH are in range results. I just asked simply .... well in that case why do I still feel like a train crash. We discussed it and I was bold and said ..... I read that i may not be using the T4 properly if vitamin D levels were low would be mind testing. So he did T3 and vitamin D. Results .... very low levels of both. Action ..... prescribed Vitamin D. Taken it ever since. Felt sooooo much better within two weeks.

I asked three times, and paid for two private tests, before finally being given an NHS vitamin D test. They did deign to give me a prescription on the basis of a rather low result of 39 (ng/L I think). Under 50, but not desperately low is classed as insufficient But it was a mixture of vitamin D with calcium, of only 800iu per day, which (in a temperate climate) is barely enough to keep a healthy person well. The calcium, which I don't need, meant it was impossible to take the 4,000-8000iu per day I had been taking (Plus vitamin K and magnesium). So I had to carry on paying for my own.

By the time I finally got an NHS test my levels were up in the 90s. Not bad going - the optimum is supposed to be between 100-150. The results were accompanied by a snooty sounding comment from the lab saying that most people are OK on 50 (bottom of the range), and no more tests were needed.

I felt like sending them an equally snooty letter saying that hypothyroid patients are not "Most people", and that we need an OPTIMAL level of at least 100 in order to make proper use of thyroid hormones!

Finally, after more nagging I got a prescription of D3 on its own, but still only 800iu per day. A monthly pack of 30 lasts me less than a week - better than nothing I suppose.

The ignorance of professionals is appalling!

vocalEK profile image

This calculator helps you figure out how much Vitamin D you need to take to reach a specified blood level goal. My goal is 60 ng/ml because the researchers on that site have found that sufficiently high blood levels help to prevent many types of cancer. I have survived lung cancer and am at increased risk for breast cancer. Remember, if you are taking high levels of Vitamin D, you need to also take a small amount (90 - 100 mcg) of Vitamin K2-MK7, which helps the Vitamin D route your dietary calcium to bones and teeth instead of being deposited into soft tissue.


By taking 5,000 IU of Vitamin D3, I raised my blood level from 29 ng/ml to 47 ng/ml, but seemed to be stuck at that level. So I added another 5,000 IU of Vitamin D, but did not add any more of the Vitamin K2-MK7.

in reply to vocalEK

I've been told that up to 10,000iu you need 100mcg of K2(7). Is that right?

vocalEK profile image
vocalEK in reply to

Yes. I was already taking 100 mcg of Vitamin K2-MK7, so I only upped my Vitamin D.

LotiRamjet profile image

OMG - thank you thank you thank you for asking this and thank you to those who replied!! This answers so many questions I have had about my low Vit. D and thyroid issues. A talk with my doc shall be had!!! I have many many cysts in my thyroid though - which complicates it all!

Gigi216 profile image

I have wondered this too I’ve been hypo since birth of my daughter 32 years ago and have had vitamin D deficiency for quite a while

ReneeC76 profile image

Based on your iron numbers, your liver isn't working optimally. You more than likely have a methylation issue. You need to address your liver function when you have an autoimmune disease or any thyroid issue.

I'm a nutritionist and I advise meal plans and supplementation for a local wellness group. Patients with any form of thyroid issue are told to optimize vitamin intake. The problem with taking this at face value is, you can pour as many vitamins and supplements down your throat as you want but if your liver is not metabolizing and utilizing, the supplements can be useless or even cause some harm.

It's not enough to know your vitamin D levels. It's not enough to look at your iron levels. The whole picture has to be assessed, starting with the liver.

Low thyroid means sluggish liver. Sluggish liver causes low thyroid function. Inflammation causes sluggish liver. Sluggish liver causes inflammation. Vicious circle.

Your thyroid hormone won't do you the most good unless your liver functions properly. And you can supplement yourself like crazy but if your liver isn't optimal, your body isn't utilizing the supplements correctly.

Start with liver supporting herbs and a very mild liver cleanse. Then work on the appropriate supplementation and possible adjustments to your T4 or T3. After this, at some point when your feel up to handling it, look at a liver detox.

No, it probably isn't as simple as possibly just needing some vitamin D based on your vit D labs. Yes, you need it but you have to address your liver function before you can expect anything at all in your body to function properly. You have thyroid problems? Your liver needs help.

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