Private test a week or two between our at the same time as GP?

I ordered a private test for ft4, tsh and ft3. What would you advice to take on the same day as the GP test or is it ok to take it a week or two in advance? What is best and why? I want to increase my dosage of levothyroxine because I don't feel well and that's the reason for having tests done.


28 Replies

I don't understand. Are you trying to compare the accuracy of the private tests v the GP test?

No, the reason for me ordering the test is that my GP won't test my ft3.

I know that feeling i just done a ft3 test mine came back over double the top range. Im also pregnant.

I used medicheck, within two days i had result.

Did you take it at the same time as your GP test or in between?

No my gp refused test completly for ft3 , my test for tsh and t4 that came back normal was a week ago. But my heart rate is always over 100bpm in the day, bad anxiety, fatigue and 8lb in weigtht loss since geting pregnant.

Whenever you do it, it needs to be at least six weeks since your last change of dose, because it takes that time for the change to take effect. Apart from that, it doesn't really matter when you do it.

Does it take 6 weeks for the ft4 to show the effect of the dose or is it just the tsh?

Sorry? That's the same thing, isn't it? It will take six weeks for the T4 you're taking, to be absorbed and synthesised, converted, which will raise the FT4 and the FT3 and lower the TSH. It's the whole package.

Sorry, of course You're right. 😊

Since I only increased with 12,5 mcg levo. Would it make a big enough difference to wait 6 weeks instead of 4 to adjust dose? I guess that since it's so small it had little impact...

No, it doesn't work like that. You still need to wait the full six weeks.

A change to dosing starts to have an impact pretty much immediately - but it takes several weeks for everything to stabilise.

It would be great if we could be tested every day - but on the basis that we only rarely get a test, it is important for it not to be while things are still likely to be changing. It really doesn't matter whether we are talking about TSH, FT4 or FT3 - we have to leave it long enough.

In the leaflet that comes with the levothyroxine it says every​ 4 weeks when adjusting dose. But you have to wait 6 weeks?

If you could have a test every four weeks, at least while still changing doses and for some time after, that would be fine. As this is unlikely, it is probably best to be as sure as you can be that the impact has stabilised.


I did my last medicheck test half an hour after having my NHS blood draw, partly because I wanted to reassure myself that the tests were comparable but also because I knew NHS would not test FT3. I was glad I did as my TSH was low and FT4 at top of range so GP started making lowering dose noises. After comparing the two sets of results she had no reason to dispute the accuracy of the FT3 which was well within range. She agreed to leave my dose alone much to my relief as I was feeling the best I had since diagnosis and she also asked for a copy of the private results to attach to my records. (good GP makes such a difference).

I always make sure there is a week between bloods (NHS or private) and any GP appt to make sure I have plenty of time to take advice/gather any required ammunition.


Were the Medicheck TSH and T4 result the same as the NHS result?

All my results are on my bio. The TSH was identical. The FT4 was slightly different with the NHS being just above rang and the medichecks a hair inside range. Gp was happy to put that small difference down to the difference between a veinous/fingerprick sample and handling differences. I doubt two samples sent to the same lab but dealt with separately would be identical due to equipment calibration. Might have been harder if their Precious TSH had differed, lol. She also accepted the medichecks deficient vitamin test results and agreed to treat, a lot depends how open your GP is to common sense I suppose

Many thanks,

I have just sent mine to Medichecks but Doctor has now agreed to do them on Monday. I wonder if there will be much difference in the one done yesterday and the ones I will have on Monday.

Most levels are fairly slow to change but the Ft4 may vary if there is a big difference in test time after last dose and TSH is likely to drop if the second test is much later. Just try to mirror conditions as best you can, ie try for a similar time test with the same sort of time since last dose as medichecks ones and hopefully you will have consistent results. I am assuming you followed best test practice, ie early fasting test and about 24 hours since last levo

I am taking NDT and was advised to leave 12 hours from last dose and blood test. I did fast.

Hope this is right and not messed the test up,

Sounds about right from other advice I have seen, sorry hadnt clocked the NDT Doh!

Is a finger prick blood test easy to do please? Does enough blood come out?

(I hope no one objects to my asking these questions, I don't want to be accused of 'hijacking' someones thread again).

Hi Ellie-Louise,

If you wash your hands in warm water then leave them in the water for a couple of minutes, then massage the finger you intend to prick downwards towards the tip, the blood usually comes out well.

Hi. I also find that the blood flows more easily from the third (ring) finger than from the middle (biggest) one, no idea why!

Have you tried them all then? Lol

I have this vision before my eyes now, and it looks as if you've had your hands in the jam jar. 😁

No, only those two fingers!

Thank you Lucy, that's very helpful.

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