Thyroid UK
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underactive Thyroid, on 400mg


I am new here. I was diagnosed with underactive thyroid when i was 9. I am 38 now. I have never really felt that the thyroxine was helping me and i currently take 400mg daily. The doctor always says my blood tests are fine and continue with the thyroxine. In the last year i have been more tired than usual and can fall asleep anytime for hours at a time. My toungue is swollen and my hair is falling out more than normal. I am also on 100mg of sertraline (anti depressant). I have been reading about Dr Skinner and wondered if anyone had any experience with him?

Thanks Samantha

7 Replies

Hi Samantha,

400mcg does seem a lot for an NHS doc to prescribe although I know that some people need a high amount. Dr Skinner has helped many people but I think that it might be an idea to check out some thing first (which will save you paying for a private doc).

Ask your doctor to check to see if you are converting i.e. do an FT3 test. If this is low you may need some T3.

Alternatively, some people do better on the natural thyroid hormone so it might be worth discussing a trial of this with your GP.

Also check your B12 and D3 levels.


Samantha, That is an unusually high dose of thyroxine! Something certainly seems wrong, and it could be that you're thyroid medication isn't working well enough for you. It's important to realise though, that the symptoms you describe can be caused by conditions other than thyroid.

Do you know when your thyroid levels were last checked? If so, do you know what the actual test results were? If you have this info, it would help if you post them here. If you don't have this info, then you can ask for it your surgery.

When and how do you take your thyroxine - what time of day and with or without food? Do you take anything else at the same time, such as vitamin pills? Are you on any other medications besides thyroid and the antidepressant?


Hi Red Apple

I am going to make an appointment at the doctor and will post my last blood results. No i dont take any other medicine except the thyroxine & sertraline


Hi Samantha,

I have just found this, read the Interactions section:-

Is this your GP that is prescribing 400mcgs? and you still have symptoms!

Apart from the Sertraline do you take iron, calcium or anti-acid tablets? or anything else?

Also do you take your levothyroxine with water and not eat or drink anything else for at least half an hour?


Suze, the link you've posted is not working for me. Can you give some explanation of what it said please?



Thats interesting about the sertraline!! I need to go back to my doctor and tell him all the info i have found from this group.

I dont take my thyroxine and not eat for 1/2 hour i never knew i had to do this! will start to do that from now on



I have copied and pasted here:-

Interactions :

Anion-exchange resins: Cholestyramine interferes with the absorption of Levothyroxine when administered concurrently; administration should be separated by 4-5 hours.

Antacids: Calcium carbonate can reduce the absorption of levothyroxine.

Antibacterials: Rifampicin enhances thyroid hormone metabolism.

Anticoagulants: Levothyroxine may enhance the effects of anticoagulants; may require reduction of anticoagulant dose.

Antidepressants: Effects of levothyroxine may be decreased by concomitant sertraline. Antidepressant response to tricyclics can be accelerated, but concomitant administration may precipitate cardiac arrhythmias.

Antidiabetics: Requirements for insulin or oral antidiabetic agents may be increased.

Antiepileptics: Carbamazepine, barbiturates including phenobarbital, phenytoin and primidone can accelerate Levothyroxine metabolism

Beta-blockers: may decrease peripheral conversion of Levothyroxine to triiodothyronine.

General anaesthetics: Ketamine may produce marked hypertension and tachycardia in patients taking levothyroxine.

Iron salts: Ferrous sulphate reduces absorption of levothyroxine

Sex hormones: Oestrogens increase and androgens decrease serum thyroxine-binding globulin; thyroid hormone requirements may be increased during oestrogen therapy and reduced during androgen therapy and thyroid function tests affected.

Sympathomimetics: Effects may be enhanced by levothyroxine.

Ulcer-healing drugs: sucralfate reduces absorption of levothyroxine


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