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Thyroid UK
91,729 members106,032 posts

T3 T4 testing?

Hi, thanks to everyone who has been so helpful in the past.

Approx 8 months ago my GP increased my levothyroxine dose from 100 to 125 mcgs, after a long battle with being concerned about being under medicated.I found that a dose of 100 mcg actually suited me better and my TSH went from 2.4 to 1.8. I am very sensitive to dose changes so have maintained that dose for several months, feeling better than I did before and losing a little weight too, which i welcomed.

However I am now beginning to get fairly regular dizzy spells and ringing in my ears , my thoughts ( mostly irrational) race and I find concentration very much harder than I used to.Joint pains have also got worse lately.

I am wondering whether now is the time to go private and have T3 /T4 tested ( GP is happy to ask lab to do the tests but the lab refuses as my TSH is so called normal)

I am concerned that the increased dose maybe causing a build up in my system which is not being utilised by cells - is this possible and could it be a T3 conversion issue -

I am taking Vit D supplements, multi vits and minerals with high level of B.+ high levels of vit c.

Any advice very welcome!



3 Replies


You are right to be concerned as many members have conversion issues. TSH can fluctuate and shouldn't be used alone as a measure of thyroid hormone levels.

Too much thyroxine whether overdosed or just unutilised can covert to Reverse T3. We all need a little RT3 to keep R3 inline but too much has negative consequences.

Have you sorted previous gut issues out ? Hypothyroidism can encourage low stomach acid that in turn can cause malabsorption issues. Nutrient deficiencies can cause thyroid hormone conversion problems & a multivit is generally not considered enough so individual supplements are recommended. If you advise what supplements and doses you are taking, members will comment.

Re other post - At my worst I suffered a feeling of swollen eyes balls which hurt when I looked to the right//left.

Members use private labs for comprehensive thyroid testing when their doctors// local health authority labs are uncooperative - link below.


Private labs testing



This following link explains the importance of vitamins and where they may be obtained.



Dr Myhill advises on Hypochlorhydria



When you get a blood test for thyroid hormones, it should be at the very earliest possible and don't eat before it. You can drink water.

Also your last dose of levo should be 24 hours approx before your test and take levo afterwards.

This allows your TSH to be at its highest as some doctors adjust dose only to the TSH and it can cause problems for the patient.

You can get a private blood test from recommended labs and some are pin-prick ones.


Your dose of levo isn't particularly high and it may not be a sufficient dose to give your receptor cells the T3 the require. T3 is the only active hormone needed in all of our receptor cells. T4 (levo) is inactive and has to convert to sufficient T3.


yes..find out what your free t4 and free t3 are and reverse t3.. very important.


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