Conflicting test results - medicheck accuracy ? - Thyroid UK

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Conflicting test results - medicheck accuracy ?

Spudley profile image

Well following a medicheck test that showed t4 30 a test by doctors has given a t4 of 16.8 ?

I’m not sure what to make of this news as I have so many symptoms of hyperthyroidism and even Dr said he fully expected to get the results and be prescribing medication based on previous test and symptoms !

Just wondered if anyone had anything similar like this happen ? Ie different results etc ?


28 Replies

There are loads of factors that can change results like that.

Some questions :

1) How many days were there between the two tests and which one came first?

2) How long between last food and drink intake (ignoring plain water) and each test being done?

3) What time of day were each of the tests done?

4) Are you being treated for hypothyroidism? If yes, what dose are you taking and what was the gap in hours between your last dose and getting blood taken?

5) Have you ever had any thyroid antibody levels tested (there are a few different kinds)? If yes, were they positive?

Spudley profile image
Spudley in reply to humanbean

Thanks for the reply

1 . Medicheck test was done on 16/11/18, drs done on 29/11/18

2. Medicheck done at 8.30pm so about two hours after tea , Drs was done in morning and hasn’t had any breakfast just a morning brew !

3 as above

4 no

5. antibodies were tested with medicheck test ( but not TRAb ) and we’re all within range

humanbean profile image
humanbean in reply to Spudley

An awful lot can change in 13 days in thyroid terms.

It is always a good idea to do thyroid testing first thing in the morning, having fasted overnight (apart from water). Delay breakfast and drinks (apart from water) until after the blood draw. Time of day makes a difference to test results, as does food intake. For any blood testing of anything it is a good idea to stick to doing the tests in the same way at the same time where this is possible - it maximises your chances of making sensible comparisons between tests.

There is a circadian rhythm to the production of TSH and T3 - see the graphs on this post :

Do you take biotin in any supplemental form? It often appears in Vitamin B Complex supplements, multivitamins, and can be supplemented alone. Biotin can affect the accuracy of blood testing, although not all testing protocols are affected. See these links :

Antibody levels do fluctuate, often quite dramatically. If TPO and/or Tg antibodies are positive it confirms the presence of Hashimoto's Thyroiditis (known to patients as Hashi's, known to UK doctors as "autoimmune thyroid disease" or "autoimmune thyroiditis") which eventually leads to hypothyroidism. Antibodies associated with Graves' Disease come in more than one type - binding, blocking and stimulating. I am not knowledgeable about these.

It is possible to have Hashi's and never get a positive antibody result. Having Hashi's means that your immune system attacks your thyroid, in the same way that the immune system will attack bacterial infections and viruses.

The fact that your T4 dropped so much between tests suggests to me that you have Hashi's. You were going through an active immune system attack when the first test was done, but it was over by the time of the second test. When cells in the thyroid are damaged or killed by the immune system those cells release the load of thyroid hormones that they contain. The rise of the T4 levels will then lead to a lower TSH level. When the immune system calms down again the levels of T4 drop and TSH starts to rise.

SeasideSusie profile image
SeasideSusieAdministrator in reply to Spudley


Medicheck test was done on 16/11/18

2. Medicheck done at 8.30pm so about two hours after tea

Their instructions say to post the sample to them the same day it is taken so that it arrives the next day, in order to avoid any delays and the sample spoiling. They also say to not post on a Friday or the weekend.

16/11/18 was a Friday. So you did your test on a Friday evening, possibly posted it Saturday, it may have arrived on Monday (if you used 1st class post but there's never any guarantee of that unless you use Royal Mail's Special Delivery Guaranteed Next Day by 1pm service) or it may have arrived Tuesday. Plenty of time there for your sample to spoil and results to be inaccurate.

Spudley profile image
Spudley in reply to SeasideSusie

No apologies it was done on a Thursday and posted with next day guaranteed delivery but they must have tested it on the Friday !

SeasideSusie profile image
SeasideSusieAdministrator in reply to Spudley

If you did it Thursday at 8.30pm it wouldn't have gone in Thursday's post surely. Anyway, their report will tell you the date they tested it.

How about the TSH and FT3? Were there big differences in those?

Do you take biotin - either by itself or in a multi-vit?

Spudley profile image
Spudley in reply to greygoose

Dr wanted to see me tomorrow so will ask abou those ...... I’m not taking any medications or vitamins at the moment

I can only begin to assume that the medicheck test is inaccurate and that all my symptoms must be down to anxiety but I have so many hyper symptoms......

greygoose profile image
greygoose in reply to Spudley

I don't think you should assume that. They use the same labs as the NHS - Medichecks is not a lab, they don't do their own analyses. And, if you feel hyper, it's more likely to be the NHS results that are wrong, not the Medichecks.

Ask your doctor for a print-out, because you absolutely need the ranges, too. Not just a garbled verbal run-down.

Spudley profile image
Spudley in reply to greygoose

I just can’t make sense of it all tbh ? I don’t understand how the tests can be wrong or what can make them give inaccurate readings but something is definitely not right I had the test to rule out thyroid problems so I could concentrate on dealing with the anxiety if there wasn’t a cause iykwim but am now totally confused by it all ! The dr did say that initially they hadn’t tested my t4 as TSH was normal and be rung them to sort same which is why he didn’t ring me back on Friday

Would you suggest another medicheck test or ask drs to redo one ?

SlowDragon profile image
SlowDragonAdministrator in reply to Spudley

What tests were run on the Medichecks test?

Presumably not just TSH and FT4?

Just testing TSH and FT4 is completely inadequate

With Hashimoto's or Graves' disease Thyroid levels can change dramatically from day to day

For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also extremely important to test vitamin D, folate, ferritin and B12

Low vitamin levels are extremely common, especially if Thyroid antibodies are raised

All thyroid blood tests should ideally be done as early as possible in morning and fasting.

This gives highest TSH and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)

Spudley profile image
Spudley in reply to SlowDragon

Hi yes tested for antibodies and no issues , I posted the original results before on a different thread but the only thing flagged was t4 of 30 and t3 was high but in range TSH was 2.4 and antibodies weren’t detected

Spudley profile image
Spudley in reply to SlowDragon

These were antibodies results

Thyroglobulin antibody 10.4 ( 0-115)

Thyroid peroxidase antibody <9 ( 0-39)

SlowDragon profile image
SlowDragonAdministrator in reply to Spudley

The TPO and TG antibodies are the test for Hashimoto's

But for Graves' disease you need TSI or TRab antibodies tested

As the FT4 and FT3 were high, ask GP to test TSI or TRab antibodies

Did you test vitamins?

If jog ask GP to test these and for a coeliac blood test too

Spudley profile image
Spudley in reply to SlowDragon

I will see what he says tomorrow but because there test was normal I think he will say that they won’t do any other tests. ( plus tsh was in range on private test ) I don’t think the tests you mention are available privately ? So I will just have to accept what they say x

Many thanks for your reply I will certainly mention them and see what they say

greygoose profile image
greygoose in reply to Spudley

Oh, lab error is always a possibility, that's why the three test should always be done together - TSH, FT4 and FT3 - so that you can compare them.

Spudley profile image
Spudley in reply to greygoose

The trouble is how do we know which lab result is wrong if any ? Think I will. Do another private test to compare again but will see what dr says tomorrow

greygoose profile image
greygoose in reply to Spudley

Yes, that's maybe best. But, I do think you ought to post all the results from these two tests, with ranges, to give us a clearer idea.

Spudley profile image
Spudley in reply to greygoose

I will do once I have them , it was only a quick call from dr today and he only mentioned free t4 at 16 so will ask about other results when I see him tomorrow

Spudley profile image
Spudley in reply to greygoose

I now have both results


TSH 2.34 ( 0.27 -4.20)

Free thyroxine 30.5 ( 12-22)

Free t3 6.24 ( 3.10-6.8)


TSH 0.96 ( 0.4-5)

Free t4 16.8 ( 9-19)

Free t3 4.37 ( 2.89-4.88)

I have been referred for scan and encronologist appointment )

Thanks for all your advice

greygoose profile image
greygoose in reply to Spudley

I think that medichecks FT4 has just got to be a mistake. It doesn't correspond to anything. Those are not Hashi's 'hyper' swing results, It's just totally out. I'm surprised medichecks didn't offer you a retest with that result. Doesn't make any sense.

Spudley profile image
Spudley in reply to greygoose

Dr has said my thyroid is swollen and that results are towards the high end of the range and couple with symptoms suspects hyperthyroidism, will no more with further tests and after thyroid scan

greygoose profile image
greygoose in reply to Spudley

I doubt you have hyperthyroidism as such. Your TSH is not suppressed, it's still in-range. But, if that's what he suspects, he should be doing antibody checks - TRAB or TSI.

If your thyroid is swollen, it sounds more like Hashi's, though.

Afzb0501 profile image
Afzb0501 in reply to Spudley

Hi I done a medicheck a few months ago which gave my tsh at 21.9 I then went to gp who ran a test which was tsh 8.5 I wasn’t on any medication or anything I felt the same as u confused as I wasn’t sure how it could be so out still don’t no why I just go by what gp results are as they only go by them.

MiniMum97 profile image
MiniMum97 in reply to Spudley

To reassure you about the accuracy of Medichecks tests. I have had loads of Medichecks and Blue Horizon thyroid blood tests done at exactly the same time (same blood draw) as NHS tests and the results are virtually identical.

MiniMum97 profile image
MiniMum97 in reply to MiniMum97

I agree with Greygoose though having seen your private results above, they look weird and don't make sense at all so I would push for a retest.

What were the ranges for the two tests?

Were they both done early in the morning fasting, 24 hours after last levo dose?

Hi Spudley

I've had a similar experience with private lab results being quite a bit different to NHS ones. Medichecks and Thriva use the same lab in Surrey. The first time it happened I challenged the private result and was given an explanation that the equipment used to analyse my blood was far superior to anything in an NHS lab. As that test had been a finger prick test done 30 minutes after my NHS test, I decided to get the next test done by a different company and by blood draw. I didn't realise until it was too late that the sample was going to the same lab. The result of that test was again quite a bit different to the NHS result, despite the sample being taken at the same time as my NHS test. I too now have doubts about the accuracy of private tests. I'm now trying to find a company who doesn't use the lab in Surrey to see if there's a change in the accuracy.

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