Morning and afternoon TSH number different 'I didn't know that.!

[Katy14]

Hi just read advice re time to do tsh blood test on here.

Been feeling ill for a while and latest tsh 5 week ago was 7

Done first thing morning fasting and

Dr increased my levothyroxine dose.

Over previous 18 months my 2 tsh were both 4.1 taken afternoon nonfasting

Is it possible my tsh would have been higher if done mornings then and I would have been dose increased months ago and not felt so unwell?

Thank you

Regards kate

[SeasideSusie Remembering]

Katy14

Is it possible my tsh would have been higher if done mornings then and I would have been dose increased months ago and not felt so unwell?

Yes. TSH is highest around midnight to 3am, then lowers slightly, another high at 9am then lowers throughout the day until about 1pm then starts to rise again. See first graph here:

healthunlocked.com/thyroidu...

Always advised here when doing thyroid tests is:

* Blood draw no later than 9am. This is because TSH is highest early morning and lowers throughout the day. If looking for a diagnosis of hypothyroidism, an increase in dose of Levo or to avoid a reduction then we need the highest possible TSH

* Nothing to eat or drink except water before the blood draw. This is because eating certain foods can lower TSH and coffee and other caffeine containing drinks can affect TSH.

* If taking thyroid hormone replacement, last dose of Levo should be 24 hours before blood draw, if taking NDT or T3 then last dose should be 8-12 hours before blood draw. Adjust timing the day before if necessary. This avoids measuring hormone levels at their peak after ingestion of hormone replacement. Take your thyroid meds after the blood draw. Taking your dose too close to the blood draw will give false high results, leaving any longer gap will give false low results.

* If you take Biotin or a B Complex containing Biotin (B7), leave this off for 7 days before any blood test. This is because if Biotin is used in the testing procedure it can give false results (most labs use biotin).

These are patient to patient tips which we don't discuss with phlebotomists or doctors.

[SlowDragon Administrator]

Even with TSH of 4 your GP should have increased levothyroxine by 25mcg

Bloods should be retested 6-8 weeks after each dose change or brand change in levothyroxine

Always test as early as possible in morning before eating or drinking anything other than water and last dose levothyroxine 24 hours before test

TSH should be under 2 as an absolute maximum when on levothyroxine

gponline.com/endocrinology-...

Replacement therapy with levothyroxine should be initiated in all patients to achieve a TSH level of 0.5-2.0pmol/L.

NHS England Liothyronine guidelines July 2019 clearly state on page 13 that TSH should be between 0.4-1.5 when OPTIMALLY treated with just Levothyroxine

Note that it says test should be in morning BEFORE taking levothyroxine

Also to test vitamin D, folate, B12 and ferritin

sps.nhs.uk/wp-content/uploa...

Aim is to bring a TSH under 2.5

UK guidance suggests aiming for a TSH of 0.5–2.5

gp-update.co.uk/SM4/Mutable...