Does Medicare Cover Blood Tests?
” “What is the best blood test to get for thyroid?
” “What blood test should someone with Hashimoto's get?
” “What's the difference between a CBC and a thyroid panel?
I've compiled a list of the most common blood tests ordered and interpreted by a doctor when diagnosing Hashimoto's. Some of these are also the tests you'll get when getting evaluated for other thyroid conditions, so it's helpful to know what to expect and what they mean.
What Are Thyroid Blood Tests?
A blood test is a lab test that measures the levels of various substances in the blood. Doctors often order blood tests to help diagnose and manage thyroid conditions.
Here are the most common thyroid blood tests:
Thyroid-Stimulating Hormone (TSH):
What Does TSH Do?
TSH is a hormone that's produced by your pituitary gland in response to your thyroid gland.
Most of the time, the thyroid gland makes exactly enough TSH to keep your thyroid hormone levels balanced.
The pituitary gland monitors the levels of thyroid hormone coming from the thyroid gland and makes the appropriate amount of TSH.
When TSH levels are too high or too low, it is an indication that something is wrong with either the thyroid gland or pituitary gland.
What Does a High TSH Level Mean?
A high TSH level indicates that the thyroid gland is not working properly.
TSH measurement is a very important part of diagnosing thyroid conditions.
TSH is considered high when it's above 4.0 mIU/L and low when it's below 0.5 mIU/L.
Your doctor will likely want to see TSH levels of 0.5-2.0 mIU/L.
If your TSH level is high, it means either your thyroid gland is underactive or your pituitary gland isn't functioning correctly.
Generally, if the TSH level is high, it's a good sign that you need a thyroid replacement medication, such as Synthroid or Armour.
Here's a chart that shows TSH levels in relation to what they mean.
TSH Level Ranges What It Means 0.5-2.5 mIU/L Normal levels of TSH 3.0-4.0 mIU/L Mildly elevated levels of TSH 4.1-10.0 mIU/L Moderately elevated levels of TSH >10.0 mIU/L Extremely high TSH
What Does a Low TSH Level Mean?
If your TSH level is below 0.5 mIU/L, it means your pituitary gland is not making enough TSH. This can be caused by an underlying medical condition.
No thyroid hormone is being produced by the thyroid gland, so the pituitary gland has to step up and make extra TSH in order to ensure that the thyroid gland produces the appropriate amount of hormone.
It could be that the thyroid gland is making enough thyroid hormone and the pituitary gland is just not functioning properly.
A low TSH level can also be a sign of a thyroid condition called central hypothyroidism. This happens when the level of thyroid hormone in the blood is so high that it causes the pituitary gland to not make enough TSH.
In this case, the pituitary gland is getting “brainwashed” by the thyroid hormone in the bloodstream, and it's not producing TSH.
A low TSH level is also a sign of hyperthyroidism, which occurs when the thyroid gland makes too much thyroid hormone.
TSH levels of below 0.5 mIU/L are considered abnormal, so your doctor will want to check your free T4 level to further test your thyroid.
Your doctor may want to order testing for other thyroid hormones, too.
If your TSH levels are low, your doctor may recommend a medication called T3, or Liothyronine.
What Does Free T4 Do?
Free T4 is a pretty important hormone in the thyroid hormone cascade. It's one of the most common thyroid blood tests.
Free T4 is a form of thyroid hormone that is available for use by the body.
Blood levels of free T4 are used to make sure that the thyroid gland is working properly.
If the pituitary gland is not producing enough TSH, then it's not stimulating the thyroid gland to make enough thyroid hormone.
This is why TSH levels are the first test run. TSH levels are the “fire alarm,” and free T4 levels are the “fire engine” that responds to it.
If TSH levels are low, then the pituitary gland is not stimulating the thyroid gland to make enough hormone, and it's the free T4 levels' job to try and make up for it.
If the free T4 levels are low, then there is not enough thyroid hormone being produced and the body is not functioning properly.
In this case, the body can't use the thyroid hormone that is in the bloodstream, so it sends a message to the pituitary gland to make more TSH to try and stimulate the thyroid gland to make more thyroid hormone.
What Does a High Free T4 Level Mean?
If your free T4 levels are too high, it means that your thyroid gland is overstimulated and making too much thyroid hormone.
High free T4 levels could be a sign of hyperthyroidism, which occurs when the amount of thyroid hormone in the blood is too high. This can be caused by