What Can Affect Thyroid Test Results
Many factors may affect thyroid test results. And, so, variation or abnormalities in thyroid test results could be related to:
Age:TSH levels tend to naturally increase with age.
Time of day:TSH levels are often higher in the evening.
Stress or recent illness: Both of these can lead to a temporary decrease in all thyroid function tests.
Fasting: Fasting can lead to higher TSH values.
Pregnancy: Thyroid levels change throughout a womans pregnancy. So much so that different reference levels are recommended for each trimester to account for these changes.
Medications:Several medications may interfere with thyroid test results, including heparin, phenytoin, and amiodarone. And any estrogen supplementation which are often found in birth control pills can falsely elevate total T3 and T4 levels.
Biotin supplements: Some people take this for skin and hair health, and it is known to falsely decrease your TSH level. It is also found in most multivitamins, but the level of biotin is too small to make an impact.
Be sure to discuss any abnormal results with your provider. They can help you figure out what your results mean for you and your health, or even if they should be repeated on a different day.
How To Order Your Lab Tests
If your doctor is ordering thyroid labs for you, be sure to request a copy so that you can see them for yourself and ensure that they are interpreted correctly.
Additionally, I have included self-order options for most of the labs discussed, in case your current doctor wont order the labs for you.
The self-order options are discounted panels that I set up with Ulta Labs and can be ordered almost anywhere in the U.S. . You will receive a lab order that can be taken to your local lab, and the results will be sent to you electronically.
You can order each individual test that I recommend below, or you can order the entire discounted panel here.
In many cases, you can self-order the labs and then send the receipts for reimbursement to your insurance.
Now, lets take a look at each thyroid test and what they mean for your thyroid health.
Why Would I Need These Tests
The thyroid gland‘s hormones help control some of your body’s metabolic processes, such as heart rate, blood pressure, body temperature and weight. Too much or too little of these hormones can make you ill.
You might need thyroid tests if:
- you have symptoms of hyperthyroidism or hypothyroidism
- you are taking some form of thyroid hormone replacement treatment
- you are female and being investigated for infertility
Very rarely, babies are born without a working thyroid gland. For this reason, all Australian newborns are screened for hypothyroidism with a TSH test using a drop of blood taken from a heel prick.
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What To Consider In Your Personal And Family Medical Histories
Its important to give your physician as many details as possible about your personal medical history, as well as family history . Be sure to discuss:
Your general state of healthparticularly any changes you have noticed in your general overall health.
Your familys health historyespecially if a close relative has been diagnosed with hypothyroidism .
Whether youve ever had , or radiation to your neck to treat cancer.
Any medicines you may be taking that could cause hypothyroidism .
How Does A Blood Test For Hypothyroidism Work
How to test for hypothyroidism?
Itâs important to note that there is no hypothyroidism test that can check thyroid hormones andâbased only on those test resultsâconclusively determine if someone has hypothyroidism. Thatâs because both thyroid hormone testing and a physicianâs evaluation of symptoms and medical history is required for a diagnosis.
A blood test for hypothyroidism is based on your levels of thyroid-stimulating hormone and the thyroid hormones T3 and T4. Because TSH signals the thyroid gland to produce more thyroid hormones, unusually high TSH levels can mean that your thyroid isnât making enough hormones.
A thyroid lab test might also measure T3 and T4 to reveal just how low your thyroid hormone levels are, which can help your healthcare provider decide on a thyroid treatment strategy.
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Taking A Thyroid Test
The thyroid panel test is performed on a blood sample. If a doctor performs the test, the blood sample comes from drawing blood from a vein with a needle. And if the test is being performed at home, the kit typically contains a lancet, which pricks the finger to draw blood that you place on a card to send back to the lab.
Reading Other Thyroid Test Results
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How The Thyroid Works
Just as the thyroid gland communicates with other organs through the hormone it produces, the pituitary gland in the brain communicates with the thyroid through a hormone it makesthyroid-stimulating hormone, or TSH. When the pituitary senses that thyroid hormone levels are too low, it releases more TSH to coax the thyroid into action. When the thyroid is nudged by TSH, it produces thyroid hormonea large proportion of which is thyroxine and a smaller proportion triiodothyronine . The T4 is eventually converted into T3, the “active” form that is taken up by receptors in body cells.
What Should I Do With The Analysis
You should use the analysis to empower yourself and learn more about your results, but not to diagnose yourself with a thyroid-related condition, such as hyperthyroidism, hypothyroidism, Graves disease, or Hashimotos thyroiditis. Proper diagnosis and treatment require a holistic look at your previous medical history, symptoms, lifestyle, and more. Your doctor is the best person to do this.
You can use this information to inspire questions or use it as a starting point for a conversation with your doctor at your next appointment. Asking the right questions can help you know what to expect.
Also, consider bringing along a doctor discussion guide for even more guidanceit lists common vocabulary terms your doctor may use and important questions about symptoms, causes, diagnosis, treatment, and living well with thyroid disease.
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What Is Thyroid Disease
Some diseases of the thyroid or pituitary gland cause the thyroid to make too much or not enough thyroid hormone:
- If the thyroid is overactive, it releases too much thyroid hormone, causing . The body use up energy more quickly than it should, and chemical activity in the cells speeds up. Symptoms include sweating, trembling, weight loss, and fast heartbeat.
- If the thyroid is underactive, it makes too little thyroid hormone, causing . The body uses up energy more slowly, and chemical activity in the cells slows down. Symptoms include tiredness, feeling cold, constipation, dry skin, and slow height growth in children.
What Do Thyroid Function Tests Measure
Thyroid function tests check levels of hormones and antibodies in the blood. And, most of the time, a provider will order several of these tests together to get the overall picture of your thyroid function.
Here are the different types of thyroid tests, what they measure, and the role they play in your thyroid health:
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Thyroid Stimulating Immunoglobulin Test Results
Following are sample results of the Thyroid Stimulating Immunoglobulin blood test. The reference intervals indicate the normal ranges and the flag indicates a result outside of those ranges.
- High levels of TSI in the blood can indicate the presence of Graves disease, which is an autoimmune disorder that affects the thyroid gland. Graves disease may lead to or be the cause of hyperthyroidism.
- TSI levels may also reveal other thyroid disorders such as Hashimotos, which is one of the most common causes of hypothyroidism.
Thyroid Stimulating Immunoglobulin reference range: 0 to 139.
Tsh And Free T4 Test Results
Following are sample results of the TSH and Free T4 blood test. The reference intervals indicate the normal ranges and the flag indicates a result outside of those ranges. A TSH blood test is commonly ordered when thyroid problems are suspected. Free thyroxine tests may be used to help evaluate and asses thyroid function for thyroid conditions such as hyperthyroidism and hypothyroidism.
- Low levels of TSH in the blood may indicate an overactive thyroid gland, thyroid gland, commonly referred to as hyperthyroidism.
- High levels of TSH in the blood may indicate an underactive thyroid gland, commonly referred to as hypothyroidism.
- Elevated Free T4 results may indicate hyperthyroidism.
- Low Free T4 results may indicate hypothyroidism.
TSH reference range: 0.450 to 4.500 uIU/mL. Free T4 : reference range .093 to 1.60 ng/dL.
Quest Diagnostics Example
TSH reference range: 0.40 to 4.50 mIU/L. Free T4 reference range: 0.8 to 1.8 ng/dL.
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Who Else Can See My Lab Results Or Personal Analysis
We take online privacy very seriously, especially when it comes to individual and personalized health information.
We do not track which lab tests you analyze and we do not store any lab values you enter. You are the only one who can see your analysis. Also, you will not be able to return to your results, so if you would like to save them it is best to print them.
Tsh Levels: What Do High And Low Levels Mean
“Normal” results depend on factors like male or female sex and age
Dr. Danielle Weiss is the founder of the Center for Hormonal Health and Well-Being, a personalized, proactive, patient-centered medical practice with a unique focus on integrative endocrinology. She enjoys giving lectures and writing articles for both the lay public and medical audiences.
High thyroid-stimulating hormone levels based on a TSH test may mean you have hypothyroidism , while low TSH levels suggest hyperthyroidism .
TSH values are described as follows:
- Normal: Between 0.4 and 4.0 mU/L
- High: Over 4.5 mU/L
- Low: Under 0.4 mu/L
But, there are exceptions to these interpretations as well as variations as to what a “normal” TSH level is. This is because TSH levels can vary by age, male and female sex, and other factors. In the end, the results need to be interpreted alongside other thyroid function tests to make the correct diagnosis.
This article looks at the causes of high and low TSH levels, what they mean, and the various factors that can influence test results.
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Optimizing Thyroid Medication Absorption
Before we talk about timing your lab draw, lets review how to take thyroid medications for proper absorption.
I recommend that you take your medication consistently at the same time each day, with a glass of water, at least 30 minutes before food. Avoid taking acid reflux medications, magnesium, calcium, and iron supplements within four hours of taking thyroid medication, as they can impair thyroid medication absorption.
Absorption may also be impaired by foods such as soybean, cottonseed, walnuts, and fiber.
Beverages can impair absorption as well. Of note, coffee can reduce the absorption of T4 in the intestines.
However, hot lemon water is an exception. Taking your thyroid medication with hot lemon water can offer the acidity needed to aid absorption .
Radioactive Iodine Uptake Test
A radioactive iodine uptake test, also called a thyroid uptake test, can help check thyroid function and find the cause of hyperthyroidism. The thyroid takes up iodine from the blood to make thyroid hormones, which is why this is called an uptake test. Your health care professional may ask you to avoid foods high in iodine, such as kelp, or medicines containing iodine for a week before the test.
For this test, you will swallow a small amount of radioactive iodine in liquid or capsule form. During the test, you will sit in a chair while a technician places a device called a gamma probe in front of your neck, near your thyroid gland. The probe measures how much radioactive iodine your thyroid takes up from your blood. Measurements are often taken 4 to 6 hours after you swallow the radioactive iodine and again at 24 hours. The test takes only a few minutes.
If your thyroid collects a large amount of radioactive iodine, you may have Graves disease, or one or more nodules that make too much thyroid hormone. You may have this test at the same time as a thyroid scan.
Even though the test uses a small amount of radiation and is thought to be safe, you should not have this test if you are pregnant or breastfeeding.
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What More Should I Know About Thyroid Blood Tests
Ranges noted here are approximate your providers may differ slightly. Its important that you remember abnormal readings do not necessarily mean a thyroid disorder is present, as each test can be affected by a variety of factors.
No preparation is required for these tests. They can be taken any time of day without fasting.
How To Test For Thyroid Problems At Home
How to check your thyroid hormones at home?
The Everlywell at-home thyroid test can tell you if your thyroid hormone levels suggest hypothyroidism. This thyroid function test requires only a few drops of blood as a sample. After getting your online test results, you can easily see your levels of thyroid-stimulating hormone , free T3 and T4, and TPO antibodies. High TSH levels and/or low T3 and T4 can indicate hypothyroidism.
You can also take our thyroid test at home to check your hormones for indications of hyperthyroidism. Hyperthyroidism means your thyroid gland is overactive: itâs producing too many hormones. Low levels of TSH and/or high T3 and T4 can suggest hyperthyroidism.
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Drawing Blood For Thyroid Function Tests
Before you get a blood draw to check your thyroid levels, talk with your doctor about any medications youre taking. Also let them know if youre pregnant. Certain medications and being pregnant may influence your test results.
A blood draw, also known as venipuncture, is a procedure performed at a lab or a doctors office. When you arrive for the test, youll be asked to sit in a comfortable chair or lie down on a cot or gurney. If youre wearing long sleeves, youll be asked to roll up one sleeve or to remove your arm from the sleeve.
A healthcare professional, like a technician or nurse, will tie a band of rubber tightly around your upper arm to make the veins swell with blood. Once the healthcare professional has found an appropriate vein, theyll insert a needle under the skin and into the vein.
You may feel a sharp prick when the needle punctures your skin. The healthcare professional will collect your blood in test tubes and send it to a laboratory for analysis.
When the healthcare professional has gathered the amount of blood needed for the tests, theyll withdraw the needle and place pressure on the puncture wound until the bleeding stops. They will then place a small bandage over the wound.
You should be able to return to your typical daily activities immediately.
Controversies Over Optimal Tsh
Many non-modifiable factors influence a person’s TSH levels and dictate what a “normal” value is in an individual. This not only includes variations by a person’s biological sex or age but fluctuations that regularly occur during different seasons of the year.
Some experts argue that the upper limit of a normal TSH should be loweraround 2.5 mU/L. The reasoning behind this is that the vast majority of adults without thyroid disease have a TSH value between 0.45 and 4.12 mU/L. This is especially true in younger females.
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Thyroxine Triiodothyronine And Tsh Levels
The main job of the thyroid gland is to make the hormone thyroxine, also known as T4 because it has four iodine molecules. The thyroid also makes the hormone triiodothyronine, known as T3 because it has three iodine molecules, but in smaller amounts, explains Cathy Doria-Medina, MD, an endocrinologist with HealthCare Partners Medical Group in Torrance, California. The thyroid gland makes mostly T4, the T4 has to be converted to T3, because T3 is the part of thyroxine that actually does the work, she says.
The pituitary gland at the base of the brain controls hormone production in your body. It makes thyroid-stimulating hormone , which tells the thyroid gland how much T4 and T3 to produce. The TSH level in your blood reveals how much T4 your pituitary gland is asking your thyroid gland to make. If your TSH levels are abnormally high, it could mean you have an underactive thyroid, or hypothyroidism. Thats because it indicates your pituitary gland is producing more TSH in an effort to stimulate your thyroid to produce thyroid hormone, according to the Mayo Clinic.
TSH levels go in the opposite direction of your thyroid hormone, Dr. Doria-Medina explains. If youre making too little thyroid hormone, your TSH will go up. If youre making too much thyroid hormone, your TSH will go down.
If your TSH is higher than 4.0 mU/L on repeat tests, you probably have hypothyroidism.