Thyroid UK
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T4/T3 Ratio

Hi Guys,

Currently just on T4 treatment only, just had a blood test that as usual shows I am on 'way' too much levo at 175 mcg, have a docs apt. in a few weeks t discuss and will as usual be told to lower my dose. Results are:

Serum Free T4: 27.0 pmol/L (range:11.00 - 23.00 pmol/L)

Serum TSH: <0.05 iu/L (range: 1.00 - 5.50mu/L) (unmeasurable)

In the past I have felt well being over treated on levo only, but lately have been feeling like I am being under treated, even on 175 mcg, but as above results now show, I am awash with levo, can this be the reason I am feeling, tired (all the time), struggling to lose any weight (even though I am a recreational athlete and am well clued up on diet etc), brain fog blah blah blah...? And rather week...!

Had a million and one other test done at the same time, such as:

Serum B12 levels: 885 ng/L (range: 190 - 900ng/L) - is this not a bit high??

Serum Ferritin: 216 ug/L (range: 20.00 - 250ug/L) - is this not a bit high also?

Serum Folate: 19.4 ug/L (range: 2.00 - 19.00ug/L) - and this appears to be a bit high also...?

HbA1c levl - IFCC Standardised (none fasting diabetes test): 31 mmol/mol (range: 20.00 - 42.00mmol/mol)

I take a B12 spray daily.

I take one ferrous sulphate daily.

I take a good B Vitamin sup, two a day.

Anyway onto my main reason for posting...the doc will tell me to lower my levo, so I want to say to her I will, but I want to stat taking T3 also, which I will probably have to buy privately, as last time I asked to see an endo, I was told I wasn't bad enough to see one. So, I know you have to lower the T4 when you take T3, but to how much should I lower it guys, based on me taking 175 mcg at present?

Many thanks! :-)


8 Replies

Forgot to say...had my Free T3 tested last year:

Result: 4.4 (range: 3.1 - 6.8)


JillOliver, Some people need higher levels of FT4 to produce sufficient levels of FT3 and FT4 27 in your range isn't unreasonable. See Dr. Toft's comments in Treatment Options

FT3 4.4 is less than halfway through range so adding T3 should be helpful. I'd lower Levothyroxine (T4) by 37.5mcg and add in 12.5mcg T3 (which is an equivalent dose) and split it into 2 doses 8-12 hours apart. You might want to start with 6.25mcg T3 for the first week while the higher dose T4 washes out and to see how you tolerate T3. You'll need a pillcutter to split the tablets but 25mcg tablets are quite large and easy to quarter.

FT3 should remain within range so have a FT3 test 6-8 weeks later and before increasing further. You can order private tests from Blue Horizon and Genova via


You are a star Clutter!! Thank you very much for the reply! At least I have somewhere to start now. Before I went on holiday last week I had been asking for info in NDT, but have had second thoughts and would like to try the T3/T4 combo as I am scared of trying NDT, it being something completely different.

Thanks again :-)


Gill, Once you're on T4+T3 it's an easy transition to NDT if you want to try it later. NDT is basically T4+T3 combined.

I've never tried NDT as T4+T3 worked for me and I'm not one for fixing what ain't broke. The proportions of T4:T3 in NDT wouldn't suit me anyway.

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Of course! I forgot that NDT IS a combo!


Clutter, do you think you can PM me where you get your T3 from please? Do you get yours via private prescription or just buy without? I would be buying without prescription.

Thanks again! :-)

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DO NOT let your doctor lower your meds based on blood tests alone EVER!!


Hi Glynisrose,

I agree and I never do usually, but must admit I have been feeling rather off colour lately and am wondering if it's because I am awash with levo...or of course it could be because I am on yet another deferent brand of levo and it just doesn't agree with me! Which I will also be discussing with the doc to!



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