I keep seeing mention of a blood testing protocol. Steps that should be taken when having blood taken for testing. All ive ever known is to not take thyroid beforehand.
What is this protocol? As i have my monitormyhealth kit ready to take bloods as my GP surgery's new contract with a lab, have stopped testing ft4 ad Ft3
I remember seeing something about taking it before a certain time, like 9am, which is impossible for me.
metamorphica
Many doctors adjust dose by looking at TSH only. This is wrong because TSH is not a thyroid hormone, it's a pituitary hormone, it's T4 and T3 that are the thyroid hormones and that's why it's important to test FT4 and FT3 and use those results rather than TSH, and the FT3 test is the most important.
Because so many doctors only look at TSH, then to avoid a reduction in dose or when looking for an increase we need the highest possible TSH. TSH is highest eary morning and lowers throughout the day, you can see this from the first graph here:
healthunlocked.com/thyroidu...
TSH is highest between midnight and about 4am then reduces and the next highest point is 9am after which it lowers considerably throughout the day until it starts to rise again about 9pm. This is why 9am is the best time to test if the GP only looks at TSH.
Always advised here, when having thyroid tests:
* 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.
* 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. 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). See
thyroid.org/patient-thyroid...
biotin use can result in falsely high levels of T4 and T3 and falsely low levels of TSH
These are patient to patient tips which we don't discuss with phlebotomists or doctors.
I'm on NDT so my TSH is repressed and as i said it is impossible for me to test before 9am. I dont wake till past 11am, due to my schedule.
But the rest i follow anyway so that's good.
Metamorphica We need to develop our own protocol for testing so that we do the same thing every time. That way we can compare like for like.
My surgery will not do early morning appointments for thyroid so my protocol is to always get an appointment between 2pm and 2.30pm. I accept that my TSH will be at its lowest then and as this is not an issue with my GP I do not need to worry.
It is best to try to measure your thyroid hormones when they are at a low point. The spike in hormone levels comes 2 to 4 hours after a dose and is not representative of our levels the rest of the day. The lowest level of thyroid hormones will come just before your dose is due.
So it is best to decide to do bloods somewhere after the spike and nearer to the low point. To be consistent it should be the same number of hours after a dose each time.
That's good to hear, as i replied above, i dont wake before 11am due to my schedule, but tend to always do my own home tests around the same time after waking and i don't eat or drink anything apart from water beforehand and don't take my medications till after.
So hopefully that will be enough. 
The diurnal TSH cycle is based on the body clock not GMT. So, if you have the blood taken at midday it will be the same as having it taken at 8am for someone who wakes up at 7am.
that's good to know.
There is a daily cycle in TSH levels which peaks in the early hours of the morning. Sometimes patients can’t get a diagnosis so an early morning blood draw may tip the balance with a higher TSH. This applies to healthy people not taking thyroid hormone. It may not apply to patients on thyroid hormone, especially if they have a TSH that is quite low.
It’s better (not essential) to leave a gap of at least four hours after taking levothyroxine as it could give a false high fT4 (by about 5%). If you take T3 I would have the blood taken about half-way between doses so that you get an idea of average levels.
It doesn’t matter if you eat or drink before a thyroid blood test, it doesn’t affect the results. (There was one flawed study that wrongly suggested food made a difference, the authors corrected this a few years later in a second study).
Do your blood test at a time when it’s convenient for you but not within a few hours after taking T3. If it’s in the afternoon and your doctor is worried about a low TSH just tell them TSH is lower in the afternoon.
my TSH is repressed anyway as i take NDT. Luckily my Endo knows and understands this, unlike my GP, but since my GP washed his hands of dealing with my thyroid that's not a problem for him.
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