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Thyroid UK
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New blood test results, thoughts please

I have an underactive thyroid. Been on levothyroxine for years. Few years back got some T3 but late last year my source disappeared. I bought what I thought was T3 from another supplier but you guys on here told me you thought it was NDT. So been taking 3 tablets @ 60mg spread over the day. I also requested a cortisol test, which I know is not overly accurate but I cant afford to do a private saliva test.

Recently had a blood test , I stopped the NDT 24 hours prior to testing. Here are my results;

Serum free thyroxine 14.2 range pmol 12 to 22

Serum free triiodothyronine 4.4 range pmol 3.1 to 6.8

Serum TSH 0.04 mu/l range 0.27 to 4.2

Cortisol 217 no range 133 to 537. (Taken at 9am)

Vitamin D 250H 65 range 50 to 120

They also did other tests, not sure if they're relevant?

Serum calcium, phosphate, protein, albumin, globulin, urea.

Thanks for your help, invaluable as always!

13 Replies


How do you feel?

Serum free thyroxine 14.2 (12 to 22)

Serum free triiodothyronine 4.4 (3.1 to 6.8)

Serum TSH 0.04 mu/l (0.27 to 4.2)

You have a false low FT3 because you left 24 hours between last dose of NDT and blood draw. When taking NDT the last dose should be 8-12 hours before blood draw due to the T3 element in it, T3 is not detectable in the blood after 12 hours. I've seen it said that adding 20% to the FT3 result in these circumstances may give something like the normal circulating hormone, but that's purely a guess, and it would be around 5.28 if it does actually work. That still leaves room for an increase in dose if still symptomatic, but it's always best to do the test at the correct time for accuracy.

I can't help on the cortisol test I'm afraid.

Vitamin D 250H 65 range 50 to 120

Vit D is too low, I have added further comments in another reply below and deleted my original comments here.


I feel lethargic and just unwell a lot of the time. Very persistent croaky throat. I'm not taking VIt D now so dont know why it's high. Sounds like I'll have to get bloods done again. Thanks


It's not high, you just put a zero instead of an O in the test name so it looks like a number. It's 65 and around 100 is recommended.



Thanks to Angel_of_the_North pointing it out, I realise that I read your Vit D result incorrectly, mistaking the name of the test - 25OH - as being the result. My apologies. I will alter my original reply to as not to confuse anyone else, and here is the correct information:

Vit D: 65nmol/L is too low. The Vit D Council recommends a level of 125nmol/L and the Vit D Society recommends a level between 100-150nmol/L. To reach the recommended level from your current level, the Vit D Council suggests taking 3,700iu D3 daily (nearest is 4,000iu). Retest in 3 motns. When you've reached the recommended level then you'll need a maintenance dose which may be 2000iu daily, maybe more or less, maybe less in summer than winter, it's trial and error so it's recommended to retest once or twice a year to keep within the recommended range. You can do this with a private fingerprick blood spot test with an NHS lab which offers this test to the general public:


There are important cofactors needed when taking D3 as recommended by the Vit D Council -


D3 aids absorption of calcium from food and K2-MK7 directs the calcium to bones and teeth where it is needed and away from arteries and soft tissues where it can be deposited and cause problems such as hardening of the arteries, kidney stones, etc.

D3 and K2 are fat soluble so should be taken with the fattiest meal of the day, D3 four hours away from thyroid meds if taking tablets/capsules/softgels, no necessity if using an oral spray

Magnesium helps D3 to work. We need Magnesium so that the body utilises D3, it's required to convert Vit D into it's active form. So it's important we ensure we take magnesium when supplementing with D3.

Magnesium comes in different forms, check to see which would suit you best and as it's calming it's best taken in the evening, four hours away from thyroid meds if taking tablets/capsules, no necessity if using topical forms of magnesium.


Check out the other cofactors too (some of which can be obtained from food).

If you have Hashi's then for best absorption an oral spray or sublingual drops are recommended.

If you don't have Hashi's then softgels, which are based in olive oil to help absorption, would be fine.


Hi, I've been looking into buying these vitamins but not sure what dosage I need for k2 and magnesium. Can you advise please? Thank you


For K2, 90-100mcg is enough for up to 10,000iu D3.

Magnesium, you just use the dose suggested on the pack.

If using magnesium citrate, as it can have a laxative effect, start low and build up if taking the powder form (easier to titrate than tablets).


Thank you


I think the result is 65 for vit D so too low, and the 25O relates to the test name: 25-hydroxy vitamin D (25[OH]D)

1 like

Thank you AOTN, you are correct. Goodness knows how I got that wrong, I even copied and pasted the original figures from the OP's post and it didn't click! Thanks so much for pointing it out, I will correct my suggestion.


You left too big a gap between the last dose and the blood draw, I'm afraid. As NDT contains T3, it should be a gap of 8 to 12 hours. So, as a rough guide, add 20% to your FT3 level - the FT4 level will be correct. So, that would make it about 5.3, which isn't bad. But, how do you feel?

Why have you written for cortisol 'no range', then added a range? If that is the range, then your cortisol is a bit on the low side. Are you taking plenty of vit C and B vits, early morning protein and enough salt?


Yes that is the range, must have been a typo. I take Vit B but not every day cos it was too high when I was tested in October. Dont take Vit C. Perhaps I should start, although I think I get enough via my food. Early morning protein and enough salt? Maybe not. If my cortisol is on the low side what does that mean? How can I correct it?



Do you mean you take a B complex? Or vit B12? There is more than one B vit. And if you're taking B12 you should also be taking a B complex. The Bs all work together and need to be kept balanced. So, if you were taking B12, and the last result was high - which isn't really a problem because it's water soluble - then maybe now take a B complex as maintenance and to help your adrenals.

Low cortisol means that your adrenals are struggling. And they make a lot of other hormones, apart from cortisol. And low cortisol will affect how your body uses thyroid hormone.

How can you correct your low cortisol? As I said, plenty of B vits, etc. And start taking high doses of vit C. I very much doubt you get enough from your food. Perhaps enough for an average person, but not for a hypo with low cortisol. Also, plenty of rest, avoid stress as much as you can. Be kind to yourself! :)


Thank you everyone. That's a lot of info to take in !

I'll try to get my head around it all.


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