Vitamin D: For some reason, vitamin D has dropped... - Thyroid UK

Thyroid UK
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Vitamin D

For some reason, vitamin D has dropped from 89 nmol/L in March 2017 to 79 nmol/L in September 2017 and to 70 nmol/L in March 2018.

As would be expected, serum calcium dropped sharply from September 2017 and is now near bottom of the range at 2.2. Serum Phosphate has risen in direct inverse proportion to Calcium drop.

September 2017 seems to be a key time in all this. Two things are relevant to that date.

The first is that I started on NDT very successfully. I now have a TSH of 0.02 and FT4 and FT3 sitting comfortably in range.

I also weaned myself off Prozac with GP guidance. Since stopping Prozac, I have had nerve pains in my legs.

I am very tired and at my wits end with the nerve pain. i have increased B12 level to very near top of range which has helped a bit.

I want to take supplemental Vit D3 of 1000 IU. I already take prescribed Calcichew Forte which contains 1000 mg Calcium Carbonate and 800 IU Vit D3. Have taken this since 2012 when I was diagnosed with Osteoporosis. Goodness knows calcium and D3 levels would be without this.

I want to take 1000 IU Vit D3 to increase D3 and Calcium Levels.

I am concerned that this could lower my TSH and / or increase FT3 levels. These are stable and I don't want to upset these.

Any advice please?

Thank you.

13 Replies

Can you post your actual thyroid results with their ranges and are you aware when taking any form of T3 then resultsare read differently?

TSH should be suppressed, FT4 can fall in the range but FT3 should be high in its range. I suspect you may be slightly under medicated. Only your FT3 reading is accurate when taking T3 in the NDT so you can't use your results to see if you aren't. Inverting well but getting results for Vit D, B12, folate and Ferritin can give us a clue if they aren't optimal. Down worry about upsetting your stable results as they may not be correct for someone taking NDT. But guessing a little as need to know your actual figures and ranges so please add them into your question.


Hello silverfox

Since starting NDT last September (2 grains - Thyroid S), I have had two blood tests. Each has been done 24 hours after taking meds. They have shown FT3 at/near top of range and FT4 in half of range.

Oct 2017 TSH 0.02

FT3 6.2 (4 - 6.8)

FT4 18 (12 -22)

Mar 2018 TSH 0.02

FT3 5.5 (4 -6.8)

FT4 14.8 (12-22)

My endo/onc gets a bit paranoid about TSH being below 0.02 but I can live with that. What I don't want is for FT3 to go over range - have used Clutters calculation and with blood draws after 24 hour that could be iffy.

I do know that T3 suppresses TSH.

Thank you silverfox.


Those results look good. My last one showed my FT3 right at the top and like you thought if was may be a bit high so Endo suggested dropping from 1.75 to 1.5 so decided I would give it a good but go down very slowly so alternating the two at the moment but started feeling dreadful! Then found I had a boil andxbwcause of lymph node removal because of cancer I've been given a very strong antibiotic and now think my earlier problem was this problem talking over and not the fact that lowered my NDT! Nothing is ever straight forward is it!

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Hi Silverfox

I’m still mithering about whether Vit D supplementation will suppress TSH even more - or raise FT3 🙃🙃


Improving is going to improve readings if anything but it will possibly take time for it to make a difference.


Sorry to be such a pain. I’m obsessing a bit 🙃. How can readings be improved without going over range?


We are all different and can react differently so it's often the case of wait and see what happens then adjust if necessary. Plus if you go badly over range on NDT you should feel it's wrong from symptoms.

Are you taking the co factors of Vit D? These are K2 and Magnesium. K2 takes the calcium out of your blood and puts it in the bone and teeth and magnesium locks it in.

When I started Vit D and I was pretty low at 26 then my calcium levels rose and went over range. Taking Vit D increases D3 and also calcium but too much calcium means we can increase the risk of stones and calcified muscle. So getting excess calcium out of the blood is needed. My calcium levels dropped quickly once I started on the co factors.


Hello again Silverfox

Thank you for your reply. How patient you are:)

I already take magnesium and have done for some years. I plan to take K2 when I start the 1000 IU Vitamin D (plus 400 IU in a multivit I've just bought). Have ordered a 90 mcg K2 and the instructions are to take 1 or 2 tabs. Think I'll start one. I already take 800 IU Vit D in the Calcichew Forte supplement - so I'll havea daily dose of 2200 IU which doesn't sound too excessive.

Than you for helping me.

Hope you're feeling better. Antibiotics an play havoc with our bodies.

Kind regards


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Improving vitamin D is more likely to improve your thyroid hormone uptake/use. If anything it might increase TSH very slightly.


Thank you SlowDragon. I'm very grateful for comments from you and silverfox. Think I'll probably go for the supplemental Vit D at 1000 IU. I've read quite a lot about this and it seems that 1000 mg increases serum Vit D by about 28 nmol which wouldn't be drastic by any means.

I read a book yesterday afternoon by an American guy who takes 40,000 IU and above and claims to have resolved all his health problems. In general, I thin the Americans are far less conservative about Vit D supplementation.


I have Hashimotos and officially diagnosed as severely gluten intolerant, so probably need higher than average. After much experimentation I seem to need 3000-6000iu and plenty of sunshine too.

Was extremely deficient for decades (discovered when I got online access to historical test results.) Was never told or treated at the time

magnesium was very low too, so it was difficult to start on any vitamin D at all initially

Magnesium and vitamin K2 Mk7 both important when supplementing vitamin D


Although I have no evidence for this, does make me wonder if your body needs more vitamins when you're well-medicated, as everything is speeder up.


That’s a very interesting thought. Research needed 😊


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