Thyroid UK
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Room to Increase Synthroid


My latest labs were as follows:

Tsh 1.4 (.4 - 4.0)

Ft4 1.2 (.8 - 1.8

Ft3 3.2 (2.3 - 4.2)

Rt3 12 (8 - 25)

I am currently on Synthroid 112mcg.

Do I have room to go up to 125mcg of Synthroid without increasing my rt3 too much, while increasing my ft4 and ft3?

I can do a more gradual increase like .06mcg for a week, then add the other .06mcg if my labs don’t go up to where I need them.

I just don’t want to miss my optimal level by going too high, now that I am actually so close to being there.


5 Replies


There's plenty of scope to increase dose to 125mcg without overmedicating or raising rT3 too high. 12.5mcg is a small increase. I don't think you need to go as low as 0.625mcg.

1 like

Im currently in the same boat as you - I am on 112mcg of Synthroid and am going up 125. That increase in dosage is very small in terms of thyroid meds.

Im no expert, but your TSH looks OK. However you dont want to increase your T4 too much more than what you have - maybe your problem is with the actual conversion as your T3 could defo come up a bit more.

I find that selenium doesnt work for me - it makes me feel worse. However you may be different. Are you also taking zinc & D3?

Why do you want to increase your dose, are you not feeling great?

I know what defo works for me is dessicated natural thyroid, however for cost & convenience reasons I am giving synthroid one last punt to see if it will work for me. If you dont feel better on the synthroid after a few weeks I recommend you try 90-100mg of the natural stuff, if you can find a competent doctor who will be willing to prescribe it, that is......


I do take D3 (4,000 a day). I take a prenatal with zinc in it and I get a lot of zinc in my diet. There is 100 selenium in my prenatal and I take another 50mg selenium supplement.

I am actually just coming off t4/t3 combo. I do terrible on T3. My body converts fine, I just have to get my free t4 to an optimal place, 1.3 or 1.4 so that my T3 goes up to at least 3.5-3.7.

My free t3 was 2.5 two weeks ago (on 15mcg of t3/112 t4.) I felt awful and any higher of a t3 dose made me feel hyper and never raised my baseline ft3 (weird). So to go from a ft3 of 2.5 to 3.2 in two weeks by stopping t3 is pretty remarkable. It means I’m definitely a converter and my body does not like me assisting.

What are your labs like on 112mcg of Synthroid?

Do you think a 12mcg dosage increase will lower my tsh below 1? I’m hoping to remain above one but below 1.5.


I dont think 12mcg will make much difference, but nice to go to a rounder number.....

I havent done labs on my synthroid dosage - my labs were good on my previous natural thyroid.

I reckon try 125 then 150mcg of synthroid for a few days. See how you feel. I usually feel the same day if my dose is too high.

Just a note on selenium - opinion is divided on taking it. Taking too much of it can be the same as taking too much iodine. If you take a lot of Se then you are supposed to take a lot of iodine to offset it. I stopped taking Se and felt much better. Your dose is quite high. But, ultimately up to you.


50 is high you think?

There is already 100 of it in my vitamin.

Truthfully I don’t know if I can even tell a difference. I know if you eat one serving of Brazilian nuts you get 5x’s that much. I may stop my 50. I just started it last week. But the selenium in my vitamin I’ve been taking for months. My vitamin also has iodine in it and I eat a lot of seaweed.

How does the Selenium supplement make you feel?.


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