Blood tests.

[Redporti]

I’m having my TSH, Ft4,FT3 & reverse T3 blood test next week. I’m also having a cortisol blood test the next day. I know the cortisol has to be between 8-9am and fasting. Can I still take my levothyroxine the night before? Also with the thyroid tests do they have to be fasting & do I have to stop my levo? I’m having it done at 10am.

[SeasideSusie Remembering]

Redporti

When doing thyroid tests, we advise:

* 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 can give false results (most labs use biotin).

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

[Redporti]

Thank you. I take my levo at 1.30am and getting blood done at 9am so do I take the levo after or should I just wait for the following 1.30am dose.