Thyroid UK
87,486 members102,194 posts

Optimal ranges?

Hey guys -

Had a bit of a set back. My apparently wonderful GP was out of his depth. Prescribed me 60mcg of T3 (then 40) and kept cutting my T4 (was at 25mcg!)

My endo rearranged all my doses and I just had my bloods all tested.

He had changed my meds to 100mcg of t4 and lowered my t3 to 20mcg

My GP hadn't a notion about my thyroid and didn't understand that my TSH would be suppressed on t3. So he slashed my T4 twice and I ended up on 25mcg and a 40mcg of t3.

So headaches, shakes and rocketing blood pressure followed (159/120, 175/131).

This endo upped my t4 and cut my t3 to 100mcg and 20mcg.

I felt terrible. No energy and weight gain. That was 6 weeks ago.

I got my bloods done again.

My T4 is at 13 (12-22) on the 100mcg and T4 at 4.9 (3.2-6.8 )

So he's upped my t4 to 150mcg.

He says that my T3 numbers look good (but not optimal) considering the T4 was way too low. He's aiming to get my T4 to 19-21. And then he'll look at having to up the T3. He reckons that the reason I've never felt well is not because of a conversion problem but that i was never given high enough of a dose in the first place to convert enough over.

Does this sound right to everyone? I'm started on 150mcg and 20mcg split today and I see him at the beginning of May.

On the positive side antibodies have halved from 240 to 120 (<34) since reducing gluten.

I'd love any of your input and advice. ❤️

6 Replies

This is just one formula to help you calculate a dose: It is conservative, and you may have to go higher. This one uses 1.5 μg/kg, but there are others using 1.6, 1.7, and I think 1.8 too. My point is, you have to find SOME number to use as a guideline, because you can't use TSH. I'm guessing that's partly why your dose has been changed so much. You cannot dose by TSH.

I think your current doctor is on the right track and I agree with his reasoning. You don't cut someone's T4 dose just because you add T3. Normal people make both! Normal people also don't put out 20 mcg T3, and that is too much T3 for me. It may be just right, or too high or low for you too. I'm glad your doc is going to wait till he gets your T4 in a better place before changing your T3. You've already experienced the problems with too much T3!


Too much t3 was insane. Blood pressure and headaches were unbelievable.

I wasn't losing weight on the massive dose and my endo said that although T3 works, it's too erratic for me when he has no reason to believe there's a conversion problem if I was never given enough meds to have a fighting chance. Even when my TSH was 0.12 before T3, my fT4 was bottom range normal.

According to that calculation I'm on about 35mcg more than calculated. Not including the T3.


You can try calculating it with 1.8 to see a higher dose, and that should give you a low and high end THEORETICAL dose. As long as your endo doesn't go by TSH, you'll start to feel better as you get closer to your optimal dose.


He definitely doesn't. Just fT4 and fT3. My TSH is suppressed. >0.01(0.27-4.2)


Sounds like the endo doesn't know that your T4 will be lower if you are taking T3. If anything T3 is still too low. It wants to be up in the high 5s with that range. Perhaps you really don't convert. It might be better to up the T3 by 5 and leave the T4 at 100.

Are your zinc, ferritin and B12 at optimum levels for conversion?

What were your free T4 and T3 levels when you were on the high dose of T3?

1 like

I Don't think your endo knows much about thyroid, either. T4 is bound to be low when you're taking T3, the body has no need to store as much. And TSH is going to be suppressed. If he's going to continue to add T4 until the level comes up and, at the same time, give you T3, you're going to end up grossly over-dosed. And if you really can't convert it, it is just going to pool in your blood and make you ill, or convert to rT3, which isn't going to help anything. But to know whether you convert or not, we'd have to see your past results before you started T3.

Also, if you've only been on your present dose for 6 weeks, it's too early to decide this isn't working, it takes time. But, it could be you feel terrible because the T4 dose is too high and it's doing the things I mentioned above!


You may also like...