GP reduced my levothyroxine dose - latest blood... - Thyroid UK

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GP reduced my levothyroxine dose - latest blood results

GraceB profile image

This post is continuation of my previous post "GP reduced my levothyroxine dose".

I've just got the latest blood results:

TSH <0.01 (0.35 - 5.00)

FT3 4.2 (2.60-5.70) 51.6%

FT4 12 (9-19) 30%

The test was done in the morning fasting, last medication taken 24 hour prior to the test.

GP said I'm over-medicated and reduced my levothyroxine dose to 75mcg. I will add that I have been on 100mcg T4 and 31.25mcg T3 for over a year and feel myself again.

I would appreciate your advice on my latest results and the GP decision. Thank you :)

11 Replies
SeasideSusie profile image


Did you take your last dose of T3 24 hours before your test as well as Levo? If so you have a false low FT3, it was explained by SlowDragon in your last thread that it's 24 hours for Levo and 12 hours for T3. It has been said that adding 20% to your FT3 result will give an approximate level of your normal circulating FT3 but I don't know how reliable that information is.

Your endo is using your low TSH to dose by. With an FT4 only 30% through range, if your Levo is reduced your FT4 will lower even more and you may feel unwell.

If your endo knows you are taking T3 then he should know that it can suppress TSH.

Personally I wouldn't reduce my Levo but I would retest and make sure the timings of last dose of Levo and T3 are correct so that result of FT3 can be more accurate to see if the right dose of T3 is being taken.

GraceB profile image
GraceB in reply to SeasideSusie

Thanks SeasideSusie. I'm always taking T4 and T3 together first thing in the morning. How should I do it before the test? Should I delay the T3 tablet until the evening before a test to make it 12 hours? Thanks again :)

SeasideSusie profile image
SeasideSusieAdministrator in reply to GraceB


I take Levo and T3, both in one dose early morning. When I am doing thyroid tests, I know I will be doing mine around 8.30am so I make sure that the day before I take my Levo at 8.30am, and I divide my T3 into 2 doses just for that one day, one taken with Levo at 8.30 and the other before I go to bed, so there's the advised 8-12 hours gap for T3 before the blood draw.


Given the amount of t3 you are taking I suspect your tsh will always be suppressed. If you’re not careful your endo will have you on a dose of thyroxine that will take your free t4 levels under range.

I know some people do fine on just t3 but I think personally it’s better to have optimal levels of both.

In answer to your question yes you’ll have to split your dose and take t3 later in the day.

If you have to pay for your tests I’d generally say leave it until next time but with a dose reduction ( supposedly happening) I would repeat then you know the best the t3 level is. This may well reduce too slightly from a reduction in t4. Obviously you don’t convert well but it may could reduce a tad.

I repeat what seasidesusie says” does he know you take t3”.If so he should know the affects on tsh t3 has.

If not tell him asap.

Good luck

GraceeB profile image
GraceeB in reply to Howard39

Thanks a lot Howard39. Yes, both my endo and my GP know I'm taking T3. It was my endo who wrote a letter to GP to reduce the dose due to low TSH. I'm due to see my endo in a year now and I guess my GP will not go against his recommendation. He has already reduced a dose on my repeat prescription. Not sure how to go about it. Thanks again :)

Howard39 profile image
Howard39 in reply to GraceeB


that’s a long time to wait.

Yes I doubt many gps would even know enough to overrule an endo.

I have to agree with slowdragon- that level of free t4 would be too low for me also.

If after the reduction you feel unwell( use a thermometer and dose to 36,50 4 times a day) you will have to source some or get an emergency endo apt. He must have patients who struggle!!

It’s not like your free t3 is off the chart either.

I had this conversation with a gp last year. He said I don’t mind a suppressed tsh your levels are normal.( initially my t3 was 0) it’s was a huge 3.4( range 3.2 to 6.9)

I said well I’d like my t3 higher.( I had mine stopped so source my own then.)

He replied “ you don’t have to aim for the top”

I replied “ I don’t want to aim for the bottom either. There is a huge range for a reason “

I agreed to disagree.

I think it’s an illness you can’t understand unless you have it.

Good luck

SlowDragon profile image

Your FT4 is already low in range. A reduction is likely to take it under range

As others have said, some of us have found we need good levels of FT4 as well as good FT3

Personally I had under medicated symptoms when FT4 was as low as this, even with good FT3

You either have to retest 8-10 weeks after dose reduction in Levothyroxine and see how you go.

Or source some other Levothyroxine to keep dose as it is

Remember next time you test, to split the T3 dose the day before, and take last dose 12 hours prior to test

I was under the impression.Someone will correct me if I am wrong that T3 reduces the Free T4. I know that is true of NDT. It is hard to assess whether you are on the right dose looking at your blood tests alone ( although most doctors think you can) We need to know how symtomatic you are and your pulse and temp. How you feel is far more important than a few squiggles of a peice of paper.

SlowDragon profile image
SlowDragonAdministrator in reply to

I don't think Levo plus T3 works the same as NDT

In NDT, apparently the hormones are "bound" and not instantly available, they are released as needed. Often on NDT people often have low FT4 and are symptom free, but some people on NDT find they need to add extra Levo to increase FT4

Many of us find on Levothyroxine/T3 combo we need good levels of both FT4 and FT3

Suspect this endo is just fretting incorrectly about low TSH. That's unlikely to budge at all on T3, regardless of how much Levothyroxine was reduced. In fact TSH may actually go lower, especially if vitamin levels drop as direct result of Levo dose reduction.

in reply to SlowDragon

Thanks, Always learning.

LAHs profile image
LAHs in reply to SlowDragon

For what this small anecdote is worth: I take NDT at 6:00am, my T3 is through the roof until about 9:00am (discovered by accidentally taking my meds once before an appointed blood test!). I do not do much before 9:00am so it doesn't matter much. About 4:00pm I flop but I am able to drift through until bedtime about 9pm. Now, if I go for a ride on my bike, this pattern suffers a downward step, i.e. I flop shortly after the bike ride. This pattern, at least for me, follows the published T3 decay sequence. T3 is always available but is mostly used up by its half life of about 8 hours. It appears to be available upon demand by enabling me to ride a bike - but then there is not much left.

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