Free T3 levels compared to Free T4

Hi all

Can someone please tell me whether free T3 and free T4 should both be high or low at the same time? I have Hashimotos but am untreated due to being euthyroid, although I have loads of symptoms!

My standard blood result is somewhere around:

TSH of 0.35 (0.3-3.0)

Free T4 of 15 ish (12-22)

Free T3 of 5 ish (3.8-6.4)

However, my recent result was:

TSH 0.79 which is the highest ever recorded for me

Free T4 of 16

Free T3 of 6.4

So my T3 was almost high, but my T4 hadn't really gone up. I know I may be grasping at straws as I'm desperate for help but does this signify anything? Pooling of T3? Conversion issues?

Thanks all!

13 Replies

  • In an optimally treated hypo patient with normal conversion you'd expect the TSH to be around one or below or wherever it is needed for FT4 and FT3 to be in the upper parts of their ranges (generally FT4 in upper third and FT3 in upper quarter) and the ratio of FT4:FT3 should be 4:1 or less. However, the nature of Hashimoto's means that results will fluctuate with symptoms as and when antibodies attack.

    As you can see, your recent results show FT4 to be less than half way through range and your FT3 is right at the very top of it's range and your ratio is 2.5:1

  • Thank you. What does that mean for me symptoms wise? I felt more hyper at that time. Would T3 cause that?

  • I'm not medically trained so can only comment on what I've read and I don't have Hashi's so can't comment on how the antibody attacks affect people but you can go from having hypo symptoms to having hyper symptoms. Your TSH is still in range, your FT4 is on the lower side and your FT3, the one which should be in range, is at the very top so it could be that causing hyper symptoms if that is what you're experiencing.

  • Thank you for your help!

  • Paolatello,

    FT3 top of range can make people feel hyper. Both FT4 and T3 have risen which is typically due to a Hashi attack destroying thyroid cells which dump hormone into the blood as they die off.


    I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.

  • Clutter, thank you as always! Does that mean they will remain high? Or will they continue to fluctuate? My antibodies have been elevated on and off for 6 years that I know of, maybe longer!

  • Paolatello,

    They'll fluctuate. FT3 should start coming down when the Hashi attack stops. Repeated attacks cause the thyroid gland to atrophy and then it will be difficult to produce sufficient T4 and T3 and hypothyroidism ensues.

  • So it's guaranteed that I'll end up hypo at some point? I'm getting married in November and hoping to start a family at some point but I'm terrified that I'll be unable to cope or get post natal depression/psychosis. It's making me think I can't have children :-(

  • Thank you that's very interesting. How would I find out if that is the case? I have hashimoto's so I guess that's part of it, but should my free T3 be borderline high? It was right on the top limit

  • stay off the meds and heal the hasimotos! Please see izabella wentz website. I wish i had known then, what i know now.

  • In what sense? I'm on no medication

  • yes..i would not take it, had i known then, what i know now. That hashimotos can be put into permanent remission. You need to heal your immune system and concentrate on that, to feel well. I wish i was in your shoes and not were i am may be too late for me. My labs were totally abnormal, once i went to the doctor. I was given, levo and not taught about healing my body, just to take a pill and i would be great..i was not great. The levo made me very ill, as did ndt and my pituitary became damaged. This is only part of the story. Also the psych meds for years , and antibiotics too. I was so stupid .

  • Thanks. I will research more on that.

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