Blood tests

[Bigfraz76]

Hi, guys, my blood tests and siliva cortisol are being done on Saturday morning. Is there any procedure I should follow, ie, diet, not taking my thyroxine for a certain lengh of time before hand or anything else? Thanks, Colin

[SeasideSusie Remembering]

Bigfraz76

Who are you doing the saliva cortsol test with? If Regenerus or Genova they will have included an instruction leaflet with the kit and you should read this a few times and follow it carefully.

For the thyroid blood tests, is this a private test, are you doing it at home? If so it's not a good idea to do this on a Saturday. Monday to Wednesday are the recommended days, sending it back via a next day service such as Royal Mail's Special Delivery Guaranteed by 1pm Next Day, to avoid any delay with delivery and spoiling of sample. Remember to check if there are any upcoming Royal Mail strikes which may delay delivery of your sample.

If you are having the blood drawn at a clinic or hospital I would ask beforehand if the sample is going to be hanging around over the weekend before being tested, if so then I'd rearrange the timing of your test. My GP surgery never does blood tests after midday on Friday, this is because blood is collected from the surgery and taken to the hospital, picked up at midday and delivered later that afternoon. If any blood is taken in the afternoon it's kept in the surgery's fridge until the next day but they wont take blood on a Friday afternoon because the next pick up would be Monday and there's a risk the sample would spoil by delivery to the lab being delayed.

For 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.

In fact, 9am is the perfect time, see first graph here, it shows TSH is highest around midnight - 4am (when we can't get a blood draw), then lowers, next high is at 9am then lowers before it starts it's climb again about 9pm:

healthunlocked.com/thyroidu...

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.

* Nothing to eat or drink except water before the test - 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. Certain foods 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, split dose and 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.

[Bigfraz76 in reply to SeasideSusie]

Thanks