Confused over FT4 test result

I was wondering if anyone can clarify something for me.

My last test results were:

TSH 1.81

FT4 7.4

FT3 5.3

I am on 50mcg T4 and 20mcg T3 per day (although that is extremely likely to be stopped very soon if what I have read is true).

My question is, does it matter that the FT4 is below range?

My endo says it doesn't and it is low because I take T3.

My TSH used to regularly be 0.01 or 0.03, but has now crept up to 1.81.

Many thanks.

11 Replies

  • Twitchen,

    Your endo is correct :)

    What were your FT4 and FT3 when TSH was suppressed and what dose/s were you taking?

  • The only results I have for that date back to July 2014:

    TSH 0.2

    FT4 9.9

    FT3 3.7

    I don't think I had actually started T3 then, so would have been on 125mcg T4 per day.

    It is such a shame that there isn't a combined pill.

    I think that Mercury Pharma are totally out of order with the amount they charge the NHS for T3 - surely it could be sourced from Europe or America at a much more realistic price.

    So he is telling me the truth when he says the FT4 will be lower due to taking T3, that is a surprise.

  • Twitchen,

    Your FT4 wasn't very good on 125mcg and FT3 was below range. If you are symptomatic there is scope to increase your Levothyroxine to 75mcg which will improve FT4 and FT3. Higher FT4 and FT3 will bring down TSH.

    I think there is more flexibility to tweak your doses when T4 and T3 are separate.

  • I agree, but endo said all of the results were absolutely fine and no need to change current dose. You know what they are like, a law unto themselves.

  • Please post units and lab ranges. A T3:T4 ratio of 2:5 is even more T3 than the 1:4 ratio of NDT. Have you tried increasing T4 to see if that makes you feel better? I am on T3+T4=10+75, which seems to work quite well.

  • Lab ranges in my area are:

    TSH 0.4 - 4.0

    FT4 7.9 - 20

    FT3 3.8 - 6.0

    That's all the information I have and I only know that because I asked him as the FT4 range used to be 9.0 - 25.0.

  • Your FT3 is about right, close to 75% up in range. Has the doc suggested you increase T4 a bit? BTW, do you know if you are harboring Hashimoto's antibodies?

    I am on a dose of T3+T4=10+75 and do well there. My FT4 is within range (about 15% up in range). My doc has told me he has patients who do best when FT4 is low in range. All I know is, if I attempt to increase T4 to 88mcg, I can feel hyperthyroid anxiety creeping up on me.

  • Thanks Eddie83.

    Personally I don't think testing once a year is enough really - which is what I get. I asked GP quite recently about upping the T4 to 75mcg, but got a definite no because the consultant says I am okay on the 50mcg + 20mcg T3.

    Seeing the consultant again in late September - he likes to see me once a year as I am on T3 and he seems to think that can cause a risk to the heart. Is that true btw?

  • T3 causes no heart risk if your FT3 is in range. Which yours is. TSH cannot be used to support a contention of heart risk. Being hypothyroid is also a huge risk for heart problems, but we don't hear that from MDs, who are obsessed with the low TSH-heart issue.

    A problem here is that medicine is an experimental science. When I hear this consultant stating "no change", I feel like that is an abuse of authority. Unless you have the freedom to experiment, you will probably not reach an optimum dose (assuming there is one). Assuming you know what hyperthyroid feels like, and if I were in your position, I would acquire some T4 off the net and try a small increase, say 12.5mcg. I would also keep in mind the approx. equivalency of 1mcg T3 equals 3-4mcg T4. If I boosted T4 a little and then felt hyper, I would decrease T3 a little to see what works, keeping in mind that how you feel is more important than lab test numbers. Also keep in mind that a T4 dose change requires 6 weeks (6 half lives) before you have a result.

    A caveat here is: if you have Hashi's antibodies, that can cause your thyroid levels to wax and wane. Which could make it impossible to find an "optimum" dose.

  • I am on NDT (Thyroid-S) and have noticed that when I feel well (no symptoms of being either hypo- or hyperthyroid) my FT4 levels are low (0.9; ref 0.8-1.5). If I add T4 to the mix, I tend to feel overmedicated. Some may need to add T4 to T3 or NDT, but my personal experience is that FT4 levels can be low when taking T3. As someone here explained recently, the body does not need to "hang on" to that much T4 when you are taking T3.

  • Thank you for the information. I am a bit concerned that they will take my liothyronine away shortly, as I have read that the NHS are wanting to stop prescribing due to cost. Then I would be totally dependent on T4, or have to find a supplier of T3 from abroad.

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