Advice for Thyroid Blood test

[Molly161018]

Hello all, just a quick one...

I know it's best to not take Thyroid meds on the morning of a blood test to get better results, but is it advisable to fast too? Does eating make a difference to results?

Thanks in advance!

[SeasideSusie Remembering]

Molly161018

Taking your thyroid meds after the blood draw is not exactly to get better results, it's so that you don't get false high or false low FT4/FT3 results.

According to member Diogenes, scientist, thyroid researcher and advisor to ThyroidUK, eating lowers TSH. Coffee also affects TSH.

Always advised here is:

* Book the first appointment of the morning, or with private tests at home no later than 9am. This is because TSH is highest early morning and lowers throughout the day. If we are looking for a diagnosis of hypothyroidism, or looking for an increase in dose or to avoid a reduction then we need TSH to be as high as possible.

* Fast overnight - have your evening meal/supper as normal the night before but delay breakfast on the day of the test and drink water only until after the blood draw. Eating may lower TSH, caffeine containing drinks 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 will give false results (Medichecks definitely use Biotin, they have confirmed this and the amount of time to leave the supplement off).

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

[Molly161018 in reply to SeasideSusie]

Ok that's helpful - TVM