Differing test results: I’m trying to understand... - Thyroid UK

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Differing test results


I’m trying to understand a pattern in my health and wonder if anyone can explain the differing results in attached tests. The medichecks test was done at 08.30 before food or drink and the other test from gp was 3 weeks later and taken at approx 14.00 hrs after usual food and drink.

15 Replies

Can’t seem to post my 2nd pic.

Results were

Free T4 12 (9-21pmol)

TSH 0.88 (0.2-4.5 mul)

I also have high LH and FSH. I am post menopause.

SlowDragonAdministrator in reply to Jamima

You can only add one photo

Have you also had thyroid antibodies tested?

Or vitamin D?


You can test vitamin D here


Needs to be at least around 80nmol

Vitamin D is actually not a vitamin, but a pre-steroid hormone. Extremely common to have low vitamin D in UK anyway but especially with any thyroid issues

Jamima in reply to SlowDragon

Thank you SlowDragon. No I haven’t had it tested but I will. I’ve just had some low cortisol and DHEA results too so I’m just trying to piece together what might be happening.


There's only your Medichecks results, so can't compare them with your GP results. However, unless all tests are done under the exact same conditions - and your Medichecks one followed our advice - then they can't be compared. Comparing tests done at 8.30am fasting and 14.00 after food and drink is like comparing apples with oranges.

There's a daily circadian rhythm to thyroid hormones - see graphs in this post:


TSH is highest early morning and lowers throughout the day, TSH lowers after eating. TSH is affected by drinking coffee, tea, etc.

All blood test results can be affected by Biotin/B Complex containing Biotin if Biotin is used in the testing procedure (which most labs do).

When taking Levo, FT4 is lowest if you take your last dose of Levo 24 hours before test and highest if you take Levo before the test.

Edited to add:

Now you've posted the GP results, you can see the difference the later test has made to your TSH.

Your FT4 with Medichecks is 16% through range, your FT4 with your GP is 25% through range but there's too many bars on the FT4 graph for me to see well enough to compare what the levels would be like at those particular times.


Jamima in reply to SeasideSusie

Thank you SeasideSusie, I understand that now, but didn’t at the time.

Jamima in reply to SeasideSusie

But my TSH is higher later in the day than it was on my 1st test, so presumably it was even higher early morning before eating and drinking? I know this is guessing but there’s a difference and I’m trying to understand why.

SeasideSusieAdministrator in reply to Jamima

But my TSH is higher later in the day than it was on my 1st test, so presumably it was even higher early morning before eating and drinking?

Your Medichecks test, 8.30am and fasting, shows TSH at 1.46

Your GP test at 2pm after eating shows 0.88

So your TSH is not higher later in the day, it's lower.

Jamima in reply to SeasideSusie

Apologies, yes you’re right. Very foggy headed today and trying to work out what’s going on.



This test includes both Tpo and Tg antibodies

Jamima in reply to SlowDragon

Thank you, I’ll have those tested too.

Well, tests will be different depending on time of day, time of year, time of month for women and whether you have eaten or not, and when you took your meds. Medichecks test shows you need an increase in levo unless you feel great.

I’m not on any levo. I don’t take any meds.

Then you can ignore the "when you took your meds" bit. Your FT4 and FT3 are lower than most healthy people, but FT3 only a little.

Thank you.

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