It’s best to not take any thyroid meds prior to your labs, as T3 spikes rather quickly in the blood and may give you a false high reading in your labs – and your doctor may want to decrease your meds, which may not be the best thing. Skip your meds for 12 hours prior to blood work.
I also do all my labs first thing in the morning, while fasting. This gives a good baseline with fewer variables – for example, food may also affect TSH/hormone levels. Fasting lessens the chance of this variable affecting labs.
Biotin has also been known to skew labs, so it’s good to stop taking it a few days before any blood work.
So, what labs to get? A full panel consists of:
Free T3
Free T4
Reverse T3
Antibodies: TPO and TgAb (for Hashimoto’s) and TSI (for Graves).
NOTE: Some sources say that upwards of 80% of those with hypothyroidism also carry the antibodies to the autoimmune disorders Hashimoto’s and Graves. Still, it’s good to check and monitor antibodies just to be sure – and to make sure that the antibody counts aren’t rising crazily. Keep in mind that you can have elevated antibody counts and few or no symptoms – but if the antibody counts keep going up, something is going on. Best to figure it out and get it in check before you DO start to have symptoms!
Now, a word on TSH. I’ve said this before and I’ll say it again: TSH is a pituitary hormone, NOT a thyroid hormone. If the body is not making enough thyroid hormone, the pituitary gland signals the thyroid to make more hormone by stimulating it (with TSH, aka Thyroid Stimulating Hormone).
When the TSH levels go down, some doctors may think that that’s good enough and move on. However, it’s best to check the Free T3 and Free T4 labs as these will give you a clearer picture of what exactly is happening in your blood. The Free labs test the unbound hormones. Other labs (T4, total T3, etc) may test the bound and unbound – which doesn’t give as clear a picture.
If you are on an optimal dose of thyroid replacement hormone (levothyroxine, Synthroid, Amour, Naturthroid, Westhroid, etc) your Free labs should be in the upper parts of your lab’s range. Not just “in range”, but the *upper* parts.
Also, when on an optimal dose of T3 containing thyroid meds it is quite common to see a very suppressed TSH. This is to be expected and no cause for alarm, remember that TSH is a pituitary hormone, NOT a thyroid hormone. If there is enough thyroid hormone circulating in the body the pituitary gland will have little reason to stimulate the thyroid gland to make more.
If you are optimally dosed (Free T3 and Free T4 in the upper parts of the range AND your symptoms have lessened or disappeared completely) but still have a high TSH, this may indicate a pituitary issue, not a continuing thyroid issue.
To recap:
– stop taking biotin a few days before labs
– stop taking thyroid meds 12 hours before labs
– do labs first thing in the morning, fasting
– get a FULL panel, not just TSH.
If your doctor refuses to order these labs, it may be time for a new doctor…! Know that you can also self-order labs from many places online, I’ve been doing this for years due to insurance issues. Easy peasey!
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