Thyroid UK
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What should T4 be?

Hi everyone. I have been on thyroxine since last November, after a 2-3 year struggle to get diagnosed. I was started on 25mcg and then, after a blood test in March, my dose was increased to 50mcg. I certainly feel better than I did but, to be honest, I still don't feel 'well'. I have just had another blood testand my TSH level is 0.7 (0.2 - 4.5) which I know is good. My T4 is 14.1 (9.0 - 24.0) and has risen from about 12 in November. I know TSH seems to be the all-important figure but does the T4 level bear any relevance? I don't know whether these results could be the reason for me feeling unwell. I don't like to keep moaning because, like I said, I certainly feel much better than I did. I'd be grateful for any comments.

11 Replies

Well, your FT4 is certainly at the lower end. The aim of a treated hypo patient is for the TSH to be 1 or below or wherever it needs to be for the FT4 and FT3 to be in the upper part of their ranges and/or for the patient to feel well and symptoms subside.

For thyroid hormone to work properly, all vitamins and minerals need to be at their optimal levels. Have you had Vit D, B12, ferritin and folate tested? If not then please ask your GP to do them or get them done privately. While you're at it, see if you can get FT3 and antibodies tested as well.


I haven't had any tests apart from thyroid function for over a year. About this time last year, Vit D was 71, B12 was 466 (180-910), folate was 8.8. The only folate result I have is from a Blue Horizon test I had done last July - Serum Folate (guessing that's the right one) was 14.47 (10.4 - 42.4). Free T3 at the same time was 4.44 (3.1 - 6.8) but this was before I started taking Levo. Again, from the Blue Horizon test last year, my peroxidase antibodies were 234.2 (<34). I have been gluten free for years as I am Coeliac. I suppose these results are too old to mean anything now. Do you think it would be worth either asking my doctor to do them or repeat them with Blue Horizon? (By the way, I have changed doctor since last year, hence the prescription which former doctor refused to issue)


chickenmitch Unless you've been supplementing, your vitamin and mineral test results probably haven't increased. You could get a Blue Horizon Plus Eleven (includes Vit D) to be sure, but for now I'd say -

Vit D is low, I think >75 is adequate in the test results. However, a level of 100+ is better. You could supplement with D3, also K2 is needed when taking D3. Vit D aids absorption of calcium and K2 directs the calcium to bones and teeth rather than arteries and soft tissues.

B12 is low, it needs to be around 1000. You can supplement with Solgar or Jarrows sublingual methylcobalamin lozenges. Start with 5000mcg and when you reach 900-1000 you can lower to 1000mcg as a maintenance dose.

When taking B12 you should also take a B Complex to balance B vitamins. Thorne Basic B is a good one and contains folate which you need as your folate is on the low side according to the Blue Horizon test, ideally it should be half way through the range.

You said "folate was 8.8" then go on to say the only folate result is from the Blue Horizon test and was 14.47 (10.4-42.4). Did you mean ferritin was 8.8? If ferritin was 8.8 that is dreadfully low, can you please clarify because it's most important for ferritin to be at least 70?

You have high TPO antibodies, meaning you have Hashimoto's (autoimmune thyroiditis) so your symptoms and results will fluctuate as and when the antibodies attack. Being gluten free is the right thing for Hashi's patients so that's good. It will help reduce the antibody attacks. Also, a good idea is to supplement with selenium as that also reduces antibody attacks.

You could ask your GP to do all these tests, who may or may not do them all, but to be honest you'd get more done with a Blue Horizon test and they'd be back quicker. Your GP may or may not take any notice of them, but getting your own supplements means you'd probably get better quality ones anyway.

If you get up to date tests, identify any deficiencies and address them, once all vits and mins are optimal then hopefully your thyroid hormone will work better. You can then see whether your TSH and free Ts are in the best place for you. If you don't feel properly well then maybe some adjustment to your meds would be needed. If levo alone doesn't do the job there are alternatives but I'd look at the vits and mins as a first step.


Sorry - my folate was 8.8, then when tested by Blue Horizon was 14.47. Ferritin was 47.


chickenmitch Ferritin 47 is too low. For thyroid hormone to work it must be at least 70, even better would be 100-130. I would supplement with something like ferrous fumerate which is easily obtainable from pharmacies. If you find that gives you upset tummy or constipation then try something like Solgar Gentle Iron or any other brand containing Iron Bisglycinate, it is supposed to be non-constipating. Always take iron 4 hours away from thyroid meds and take 1000mg Vit C with it to aid absorption.

(Folate, as mentioned in my previous post, needs increasing but the Thorne Basic B will do that as it contains 400mcg folate)


Thank you SeasideSusie. I think I need to start taking some supplements. Didn't really know where to start so that's a great help :)


Generally, if you are just on levo, Free T4 should be in the top quarter of the range (ie 20+) and free t3 (if you are lucky enough to get it tested) about the same or slightly higher relatively. TSH doesn't really matter once you are on meds.


So if I am taking Levo but T4 is still in the lower end of the range, what does that mean? Do I need a higher dose or would supplements help? I don't really understand!


If you are T4 only, it is likely that you are undermedicated, esp if you don't feel well.


Thank you. I think my doctor will be reluctant to raise my dose though because of my low TSH - that seems to be all she looks at


You could ask Louise for the article showing that some people need suppressed TSH and over range T4 to feel well, or find a new GP, or buy some levo online and raise your dose yourself. But ask for an increase first as your TSH isn't low yet.

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