total T3 or Free T3

Hi I'm jay-jay,. I've been hypothyroid for 19 years, never felt well on t4 but I've been on t3 for the last 6 years all was well until last May 2015.

I was hospitalised for seizure in May and syncope/heart attack in August, I had a loop reveal monitor fitted after heart attack was ruled out and myocarditis was found after an angiogram. Since then I have been diagnosed with pernicious anaemia and I currently receive b12 injections every 3 months. In December I came out in hives which I've been on fexofenadine/loratadine x 4 doses a day (alternating each anti-histamine) from the dermatologist but he thinks it maybe my thyroid. The dermatologist has requested via letter for my GP to test my thyroid, I have to give blood tomorrow and on the form is just t3, I've never been tested for it before as my GP usually just tests the TSH. (Although when on t4 I got tested every year).

Would a t3 blood test be free t3 or total t3 and which would be the best to test for, not sure whether they are the same test or different.

Any help would be appreciated.

Thanks. Jay-jay

4 Replies

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  • What you need is a Free T3 test. The total T3 test tests T3 that is 'free' and T3 that is 'bound' to proteins. Bound T3 is unavailable for use by the body. So, what you need to know is how much available T3 you have in your blood, which is the Free T3 test. You can't tell that from a TT3 test.

  • Thanks for your reply, jay-jay 👍

  • Jay-Jay,

    It will probably be FT3 as Total T3 is rarely tested in the UK. Leave 12 hours between your last T3 dose and blood draw.

  • Thanks for your reply. Jay-jay 👍

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