Thyroid UK
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Low RT3

Hi everyone,

Finally had my reverse T3 result back from June! Still in Spain so the measurements are a little different..

It's very low.

rT3 0.04 ng/mL (0.09 - 0.35)

Total T3 1.35 ng/mL (0.55-1.60)

FT3 3.23pg/mL (2.00 - 6.80)

FT4 0.37 ng/dL (0.54-1.24)

TSH 0.02 mcUl/mL (0.35-5.60)

Taking T4 50mcg and T3 62.75mcg

had lots of other things tested only things slightly out were copper and zinc a little under and potassium

slightly over (too many avocados I reckon) and the antibodies are still high but have decreased slightly.

Ac.anti-microsomales 21.4Ul/mL 0-10

Ac. anti-Tiroglobulina 186.9 Ul/mL 0-4

What does it mean to have low T3?

Thanks in advance.


9 Replies

These are strange results. Are they from a finger prick test, or did you leave a long time between the last dose of hormone medication and taking the blood. The low rT3 is consistent with taking 62.75mcg L-T3 but not the low fT3. The numbers don't add up, hence my questions.


They were normal blood tests. I didn't take any T4 the night before and my last dose of T3 was at 5pm previous day. Blood taken around 9.30, they don't do it any earlier over here.


Tina, T4 converts proportionally to active T3 and inactive rT3. rT3 prevents the over conversion of T4 to T3. Your FT4 is low because you are taking high dose T3, so there isn't much T4 to convert to T3 and this is why rT3 is low. No problem with low rT3, it's high rT3 which can be a problem.

Your FT3 is less than halfway through range. If you are symptomatic increase your T4 or T3 dose.


OK Allowing for the 16 hour gap between you taking the T3 and the blood the 'real' average fT3 figure might be about 4 or 5. This is very low given you are taking 62.75 mcg daily, which is a lot, unless you are quite large. Does the T3 come from a reputable source? The fT4 figure makes sense based on 50 mcg but the fT3 figure does not. The rT3 figure is consistent with taking T3 but is of little use as nobody knows how to interpret rT3 results in any detail.

The more important question is whether you have symptoms of hypo or hyper thyroidism.


It's tiromel from Turkey. I'm a little bigger than I was a year and a half ago when everything started going wrong, I was 54kg then now I'm around 80kg I reckon although I no longer weigh myself as it's a little depressing.

I was on 150mcg T4 but something happened and I just became very ill last May so I started doing research and tried lots of things.

Recently I've found increasing my T3 meds and lowering the T4 one has started to help me feel human again.

I still have hardly any energy but since upping to T3 75mcg beginning to clear the brain fog and can go for walks again. Otherwise I'm in bed or sitting down reading.

My blood pressure is usually around 98/55 and heart rate 55-59 BPM my temperature ranges from 36.4- 36.6°C.

I used to be very fit and would do weights 3 times a week, stand up paddle, swimming, walking, hike mountains and cycle 30-40km in an afternoon.

Keen to get back to that long of lifestyle!

Thanks for your time Jim


This is so dreadful. That's a big weight increase and it's certainly not lifestyle, especially as it came on so quickly. I do think your fT3 figure is low for the amount you are taking, unless you were very large. i.e. over 100 kg. I assume you can't get L-T3 (liothyronine) from your doctor? I would tend to take my last dose of L-T3 late at night, have the blood taken in the morning and then the fT3 figure will be a reasonable average. (Maybe add on 10% to get a more accurate number).

Your symptoms suggest hypo. Your heart rate is lowish, so there's not a problem with 75 mcg L-T3, or even a bit more. My only worry is that the fT3 figure is low for the amount you are taking and this calls into question the quality of the L-T3. The danger is that if you get a good batch you might suddenly become hyper. I'd hammer your doctor to prescribe liothyronine if that is possible, I'm not sure if they have a health service where you live. I believe the Spanish doctors are rather dogmatic re thyroid.

From a finance point of view I think the only things you need to measure are TSH, fT3, fT4. rT3 and antibodies can be expensive and don't tell you anything (other than the first antibodies test).

I don't know if others have problems with tiromel, whether it is reliable. If you switch brands take care.

1 like

Thank you


Sadly they don't do T3 here so I order it in. Do other people use tiromel and if so how much do you take?

I remember reading about one of the leading doctors who took 150mcg T3 each day to be well. I'll keep on increasing slowly and see what happens.



Keep monitoring your pulse, especially if you increase. I would replenish your current batch of T3 before you finish them. Then if you find a difference with a new batch you can switch back and forth with the old batch to double check there is a difference. We have noticed differences in UK liothyronine batches and the UK T3 is regulated, so tiromel may not be as good (if good is the term to use!).


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