Blood test: Any advice please I take my T 3 at... - Thyroid UK

Thyroid UK
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Blood test


Any advice please

I take my T 3 at between 2 and 4 am, in the night. I have a blood test tomorrow. It’s at 8 am. Should I wait until after the test to take my T3? Will this give the most accurate reading? I take one quarter once only, so quite a low dose.

Also, my trans ferritin was low on medi checks. What do I ask to be tested for by GP? Can I ask for this specifically or do I ask for an iron test.

Thank you.


3 Replies


Your last dose of T3 should be between 8-12 hours before your blood test. Any longer and you will get a false low FT3 as it no longer shows in the blood after 12 hours, any closer and you'll get a false high FT3 as it will reflect the dose just taken. It would be best to rearrange the time of your Levo for a day or two before the test, to ensure the timing is right to give the correct result.

Also, my trans ferritin was low on medi checks

There isn't a "trans ferritin" test. If you had a MedichecksThyroid Plus Ten or Eleven, you would have had ferritin tested. If you had an iron deficiency check then you would have had transferrin saturation and ferritin tested. If it was ferritin - what was the result, below range or low in range?

I would take it between 8pm and bedtime instead of during the night - depends when you eat.

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