Thyroid UK
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T3 levels

Hello, I would just like to ask if anyone knows if it would still be beneficial to take T3 even if my level is in the normal range?

I still feel extremely unwell, despite being on 75 mg of thyroxin a day for 6 months. My weight just seems to increase even though I'm currently only eating about 800 cals max a day and doing exercise when I feel up to it. Sometimes I fall asleep in mid conversation with my mum when I'm at home. To say I'm upset is a massive understatement!

My blood tests show my levels do fluctuate but I have asked about T3 and my gp says its in the normal range, so I just wondered whether it was worth pursing, and I'm so desperate, I will try anything!

Thanks :)

6 Replies

75mcg thyroxine is a lowish dose. Do you have your test results? Can you post them, with reference ranges, then members can comment. If you don't have them then ask your surgery for a print out, you are entitled to them under the Data Protection Act.

If your FT3 is in range but at the bottom end then there may be good reason to add some T3. But if your FT4 is also at the bottom end you might just need an increase in your thyroxine, especially if your TSH is at the high end of the range. So it's best to have your results to get a proper picture of what's happening.

Also, are your vitamins and minerals at an optimal level? Have you had B12 Vit D, ferritin and Folate tested? These need to be optimal (not just in range) for thyroid hormone to work properly.

A low calorie diet isn't the best idea. If you aren't eating enough your body goes into starvation mode and stores as much as possible as fat. You need a good balanced diet with good fats included. I'm sure someone will come along and advise on that.

But first of all, get those blood test results posted in a new thread so members can help.


Thankyou, my gp rang me today so I will get him to print them out for me. Thank you so much for posting :)


thank you


Low-calorie diets have a negative effect on conversion. So it's possible that your FT3 is right at the bottom of the range, when it should be up near the top. For a doctor, it's all the same!

You should be eating about three times that much. And you shouldn't be exercising excessively, because exercise uses up your T3 - and you haven't got enough to begin with, by the sound of it! Just light walking, to stop your joints rusting. It isn't going to make you lose weight, anyway, any more than a low-calorie diet is, because your weight gain has nothing to do with calories. :) 

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When I was falling asleep like that, it was because my B12 was very low. We need a good level of B12 for our bodies to convert T4 to T3.  You might need a higher dose of T4.


I have now got my most recent test results back and I am awaiting an appointment with the nhs endo.

Serum free T4 level - 17.6 pmol/L

Serum free triiodothyronine level - 4.9 pmol/L

I am anxious to take T3 due my vast weight gain and generally feeling poorly than I ever have! I have a lot of swelling around my whole body, but mainly my chest, neck, tummy and face. But my lower legs and ankles are slightly swollen too.

 I have been reading that your T3 level should be high or over-high in order to work (from an American website Hyperthyroid mom) so I think mine needs to higher to work properly.

Can I self-medicate? Although, I would be happier doing it with my GP blessing, but he says to leave it to the endo.

I haven't had any B12 injections but I do take a strong vitamin B compound and thiamine tablets due to long standing disorder.

I feel very confused, alone and upset and really don't know how to go about getting some answers, it all seems like lots of information that I don't understand.

Thank you to all of you who take the time to read and reply to this, it is a massive help.


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