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Thyroid UK
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Timing of blood taken for testing

Hi everyone

I have read that blood should ideally be taken as early as possible because TSH is highest first thing in the morning but does timing have any affect on T4 and T3 levels if you are not on any medication at all.  I ask because I got my son tested with Blue Horizon as he many of the same symptoms as me, I was diagnosed underactive nearly 30 years ago.  The GP did do a test last year but as his TSH was within range at 2.3 the labs will not test T4/T3 unless previously diagnosed.

Due to my very bad brain fog I totally forgot to wait until we had a day when we could collect the blood in the morning, plus he has difficulty getting out of bed even when he has an 7:00am shift at work.  So we collected the blood at 3:30pm on Tuesday in time to catch the evening post.  Results below:


CRP 0.40 <5.0 mg/L

Ferritin 97.7 30 - 400 ug/L

Thyroid Function

TSH 0.97 0.27 - 4.20 IU/L

T4 Total 134.3 64.5 - 142.0 nmol/L

Free T4 19.51 12 - 22 pmol/L

Free T3 5.99 3.1 - 6.8 pmol/L


Anti-Thyroidperoxidase abs 15.7 <34 kIU/L

Anti-Thyroglobulin Abs 20.2 <115 kU/L


Vitamin D (25 OH) L 19 Deficient <25 nmol/L

Insufficient 25 - 50

Consider reducing dose >175

Vitamin B12 540 Deficient <140 pmol/L

Insufficient 140 - 250

Consider reducing dose >725

Serum Folate 27.19 10.4 - 42.4 nmol/

The only obvious issue is his really low vitamin D levels which we expected as the sun causes his arms to blister so he wears long sleeves all year round.  All the other results seem fine or did the time of day distort the results.

I will get round to posting my own results soon.

Any advice greatly appreciated :)

3 Replies


I think it is very unlikely your sons's TSH would be high enough to be over range if he had tested early in the morning.   FT3 lags behind TSH by around 90 minutes but FT4 remains relatively constant whatever the time of day.  See graph in healthunlocked.com/thyroidu...

TSH is low-normal, FT4 is in the upper quadrant, and FT3 is close to top of range and   thyroid antibodies are negative for autoimmune thyroid disease (Hashimoto's).  It doesn't look as though your son has thyroid dysfunction.

Your son is vitamin D deficient which may account for his fatigue.and his GP should prescribe vitamin D.  Alternatively buy D3 online and supplement 10,000iu daily for 6-8 weeks then reduce to 5,000iu daily for 3-4 months and retest.

B12 >500 is unlikely to be deficient but PA Society recommend 1,000 as optimal.  Your son could supplement 1,000mcg methylcobalamin daily with a B Complex vitamin.  Folate is good.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.



Your sons thyroid hormone results look good.  Vit B12 is good but he is deficient in Vit D and should supplement D3 with K2.

Sun blisters are caused by the sun-light penetrating the skin & activating some chemical substances we ingest or apply to our skins; in some people, this triggers an allergic reaction.  People with mismanaged auto-immune disease will suffer secondary symptoms such as a sun allergy but your son's results are negative for thyroid antibodies and he has no inflammation shown as CRP or ferritin. .

Perhaps it would be prudent to ask your GP to investigate this sun reaction further.


Does anyone know of a good soluble or chewable Vitamin B complex as my son cannot swallow large tablets. I have looked at Barocca but they look very weak compared to the B-100 Vitamin B-Complex tablets that I get from H&B, they are just too big for him to swallow.

Many thanks.


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