Thyroid UK
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Do i really need Cytomel???

I was on 125 synthroid ONLY last year and my fee t4 was 25 (range 10-25) free t3 was 4.9 (range 3.5-6.5)...and as always, my tsh is completely surpressed.

I had a total thyroidectomy 16 yrs ago due to cancer... my question is, am i converting well?

I have tried adding 10 mcg cytomel and lowered my synthroid to 100 mcg but i have gained weight and feel bloated!!!!!

Should i stop the Cytomel and increase my synthroid?????

17 Replies

Only you can decide that. How did you feel last year on Synthroid only? You do have a conversion problem, that much is clear. And, although you can keep on increasing your T4 until it's way over range, but your T3 is adequate, all that unconverted T4 in the blood can cause problems. But, it's really about how you feel, not blood tests. :)


Thank you.

Please tell me what my free t3 should like if i didn't have a conversation problem on Synthroid only.

Also...i had anxiety and hair fall on synthroid only but my weight was stabilized.

Cytomel seems to make me feel like i am retaining water.

What might you recommend i do now?

Should i go back on 125 synthroid and add maybe 5 mcg of cytomel to get me free t3 higher?

I really appreciate your time.


If you didn't have a conversion problem, the FT3 would be higher than the FT4, in their respective ranges. So, if we take that FT4 above, your FT3 would be over the top of the range, 6.5 - 7.0, something like that.

If it were me, I would go for the Cytomel every time. But, not 5 mcg. That won't do much good. More like 20, and reduce your T4. But that's me. If Cytomel makes your retain water, have you tried some form of NDT? There's nothing worse than water retention! Well, there is, but you know what I mean. :)


Oh this is all so confusing to me lol.

I read that the ratio of ft4:ft3 should equal 4.

That would mean a ft4 around 23 and a ft3 at 5.75...

In your opinion, what would perfect ft4 and ft3 look like?

I realize it's more than just numbers on paper as to how well we feel but just would like your opinion again pls.

Thx again :)


I don't have an opinion. The perfect results are those that make you well.

As for the ratios, l think they're a bit of a red herring. That may be the way they are in healthy people, but we aren't healthy people. We are hormonally challenged, and we have to find what works for us, not what some academic, with no practical experience, thinks ought to work. There are plenty of people who are perfectly healthy, with no working thyroid, on T3 only. So, they don't have any sort of a ratio, and it doesn't matter. What matters is how you feel, and what makes you feel good, and forget the rest. :)


Yoù are very correct on that!!!!!

I am at my wits end!!!!

Here's hoping I'm not one who may be allergic to it lol

Take care!

Many thx for your replies!!!


Well, it's all trial and error, you know. We have to keep trying things and seeing how we react. Nobody can tell us how we're going to react in advance. So, try a higher dose of T3, see if you have the same reactions to it. Or, try T3 only, or NDT - there are lots of NDT brands to try. Something has got to work for you. :)


I have decided to take 75 synthroid and 25 cytomel.

My endo is ok with this.

I will let you know how i do.

I will give it 2 months.

Do you have any idea as to how long it will take (in general), before i lose some weight?

Thx 😀


What do u think of this new dose greygoose?


**allergic to NDT...for some reason one of sentences got deleted😯


Allergic to NDT... you mean the fillers?


I have the same problem so will follow this thread with interest.

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My personal opinion when people have had a thyroidectomy, is that they should either be prescribed T3 only or T4/T3 combo. This is an excerpt from a Research Paper re the equvalence and if you cursor down to Page 80 on the left-hand top column.

Dose Selection in T3/T4 Study RCTs

The second logical basis for a conclusion

is the actions taken, i.e., the doses given to the

subjects. Most subjects received T3 below its

adult starting dose of 25 mcg/day.

The subjects in RCTs received T3 in some ratio to the

withdrawn T4. The various RCTs used T4:T3

ratios of 14:1, 10:1, and 5:1. Subsequent re-

search by the US National Institutes of Health

(NIH) found the therapeutic equivalence was


Thus, most of the subjects were under

treated with the T3/T4 combination. In light

of the NIH finding, the conclusion that T3

therapy is never needed is invalid.

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So the t4 to t3 ratio for someone like me, who has no thyroid gland, should be 3:1?

Sorry...again i am a little cofused lol


You seem to be thinking of the ratio as "how much T4 to how much T3 should I take".

The ratio mentioned earlier is of the effect. That is, "if you were taking 100 micrograms of T4, how much T3 would have the same effect?" The quoted answer of 3 to 1 means that 100 micrograms of T4 would be about 33 micrograms of T3. (This is a very approximate value and some people feel that the numbers should be higher or lower.)

You as an individual might need any ratio of T4 to T3 from 100% T4 to 100% T3 - though the general impression is that those with no thyroid probably need at least a little T3.

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I have read soooooo many variables of where "experts" feel the human thyroid levels should be.

Some say the free t4 should be middle of it's range and some say top.

Same with the free t3.

I have tried them all in the past 16 years.

My Rt3 is fine.

My tsh is almost always completely undetectable.

I'm sure to go on NDT next.

Should the starting dose be 90 grains?

Of course i would split the dose equally...45 grains in the morning and 45 in the pm.

Thx to whoever can answer


I think i will stick to 100 mcg synthroid and add 15 mcg cytomel to start...

I just found my old lab results when i was on 100 synthroid and 12.5 cytomel.

My results were 19.5 free t4...range 10-25

Free t3 was 5.2..range 3.5-6.5

Does leaving my synthroid dose at 100 mcg/day and increasing my cytomel dose to 15mcg/day from 12.5 mcg/day make sense?



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