High free T4

[lozza]

Been on Thyroxine for 17 years. Recent bloods show TSH at 0.58 ( I feel better in this range ) but Free T4 has been flagged at 25.6.

GP said results must be wrong and is retesting next week. I took my meds 6 hours before bloods, is this why the reading is high?

or any other suggestions why free T4 is high please?

[Jaydee1507 Administrator]

How do you feel?

You should really see an FT3 result to make a proper assessment of conversion and thyroid hormone levels.

The usual time spacing for last dose of Levo is 24 hours which will show stable blood levels of T4.

After only 6 hours you will have been measuring what you have just taken.

You have a great doctor who wants to retest you!

Recommended blood test protocol: Test at 9am (or as close as possible), fasting, last levo dose 24hrs before the blood draw & no biotin containing supplements for 3-7 days (Biotin can interfere with thyroid blood results as it is used in the testing process)?

Testing like this gives consistency in your results and will show stable blood levels of hormone and highest TSH which varies throughout the day. Taking Levo just prior to blood draw can show a falsely elevated result and your GP/Endo might change your dose incorrectly as a result.

How are your vitamin levels looking?

What are you supplementing with?

[lozza in reply to Jaydee1507]

My vitamin levels are ok, I have B12 injections and vit D supplements as deficient. From memory my T3 level was about 6? ( I think ) Will definitely not take Meds as blood test is at 8.am

[Jaydee1507 Administrator in reply to lozza]

What about your folate level? You need that for B12 as well.

ferritin?

You can really only judge thyroid levels with 3 tests taken together - TSH, FT4 & FT3. Suggest you get some private labs run.

[SlowDragon Administrator]

I took my meds 6 hours before bloods, is this why the reading is high?

Yes

Recommended that all thyroid blood tests early morning, ideally just before 9am, only drink water between waking and test and last dose levothyroxine 24 hours before test

This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip)

Just testing TSH and Ft4 is inadequate

For full Thyroid evaluation you need TSH, FT4 and FT3 tested

Also both TPO and TG thyroid antibodies tested at least once to see if your hypothyroidism is autoimmune

Very important to test vitamin D, folate, ferritin and B12 at least once year minimum

when were vitamin levels last tested

What vitamin supplements are you taking

[HealthStarDust]

I took my meds 6 hours before bloods, is this why the reading is high?

Yes.

[DippyDame]

There should be a 24 hr gap between taking levo and testing ( 12 hour gap for T3)

The 6hr gap will have caused the high FT4

Next test correctly timed will give you a reliable result.

Your GP should know this!

[Dauphin143]

I agree with the above comments and want to add that I feel best with a slightly below range / suppressed TSH & my doctor is okay with that because what is important for the body is not the TSH or T4 but the active component of T3… basically, TSH tells the body to produce T4 & after that is done, the body converts it to T3 which is what we actually need. I have had best results with a T4 / T3 combination of meds as my body did not convert well… a thyroid blood test isn’t complete without testing Free T3. When you are feeling well & your T3 is balanced (in my case, I feel best with slightly elevated T3) you can check your pulse regularly as a indicator of your dosage being correct, because changes in pulse are one of the first indicators that something may need adjusting.

[SmallBlueThing]

Maybe, like mine, it was affected by a COVID-19 infection?