# Ideal Free T3 & T4 range?



## Girlygirl90 (Jan 9, 2013)

Can someone advise the "ideal" ranges for subclinical hypothyroid (TSH only 5.25 at dx) but my T3 and T4 were always "normal range". I've been reading a lot about ideal ranges being preferred to normal lab ranges.

I have been tested positive for thyroid antibodies.

I've been on Synthroid for 5 months.

My labs came in yesterday at:

TSH 2.25
T4, free 1.3 (range .8-1.8)
T3, free 2.8 (range 2.3-4.2)

I see a GP, but just curious, what is the ideal range according to your guys' endocrinologists?

What's funny, is my TSH was always around 2.25 for the last 10 years, through 2 childbirths etc. before it went up to the 5 range after my second child.

This 2.25 must be my "normal"? But now it's taking the Synthroid to bring it back down to my "normal". Just wondering if most people aim for lower on these numbers? Since they are in range, but doctor says they are fine- no more medicine. But I'm still curious based on these "ideals" I have been reading up on.

Thanks!!


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## joplin1975 (Jul 21, 2011)

So, you want your free t4 and free t3 to be, minimally, a mid-point of the given range, with many people saying that they feel better if it is higher than mid-point...some like it to be around 75% of the range.

For your lab's ranges, mid-point of the free t4 is 1.3 and mid-point of free t3 is 3.25. So, your t4 is juuuuuuuuuuuuust at mid-point and your t3 is low.

Also of note, when you have antibodies, they can skew the results of your labs so the numbers don't always reflect how you might actually feel.


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## webster2 (May 19, 2011)

I think you will be the best judge of how well you feel. Keep track of your lab results and note how you were feeling at that time. My Free T3 is at the bottom of the range and I feel great. It is a strange and tricky business, good luck!


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## bigfoot (May 13, 2011)

Yes, we are all different. The goal of TSH at or below 1.0, and Free T3 & Free T4 at 75% of the range is just a long-term goal, not a hard and fast rule. And this isn't verbatim from a doctor, I believe it's based on everyones experiences. Like folks have said, you have to go on how you feel, not just lab numbers. You want to optimize treatment, not just be "in range" or "normal". That is the key distinction.


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## Jmobie (Jan 12, 2013)

I have a question related to this thread and optimal numbers. How long after taking a dose should we be tested? For example, the common FT3 median, 325, that I also have my eye on... should our levels be this high 8 hours after a dose, 12 hours, etc.? Or does it not really matter, as long you're not tested within x hours of taking a dose? I guess being consistent matters the most. I have been having my tests done around 9 or 10 AM, and holding my morning med until after the tests.

Thanks!


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## bigfoot (May 13, 2011)

You're right, consistency is the key.

If you take your medication before labs, the labs will be skewed, especially if you are taking any T3. I do the same thing, and try to get my labs first thing in the AM, prior to taking any morning doses. Also, FYI, TSH tends to drop throughout the day. So for those poor souls whose doctors are holding off on any treatment and going strictly by TSH measurements, that could be make-or-break.

The half-life of T3 medications (Liothyronine) is measured in hours and days, versus weeks for T4 medications (Levothyroxine).

Background info below...

http://en.wikipedia.org/wiki/Thyroid_hormone
https://en.wikipedia.org/wiki/Triiodothyronine
https://en.wikipedia.org/wiki/Levothyroxine
https://en.wikipedia.org/wiki/Cytomel


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## lainey (Aug 26, 2010)

T4 medications have a 7 day half life--skipping your medication or not before your labs has little impact. You could skip it for a couple of days, if you have been taking it long enough and not make much of a difference--your body uses the stored T4 to make T3--T4 pills do not have the same "instant" impact as T3 does.

Your thyroid levels fluctuate annually, seasonally, monthly and daily according to many factors that include but are not limited to over all health status, other hormone status, medication and changes in absorption.

There is a reasonable normal variability in thyroid numbers. The "target" is those levels across which the patient has good symptom relief--you are looking for a range, not chasing a specific number.

Thyroid dosing is individual, so to some extent it is bogus to seek "optimal" ranges. Everyone feels different at different numbers. Results posted on the internet are to a certain extent skewed as they represent a very small population of thyroid patients.


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