This article looks at 10 factors that can affect your thyroid blood test results.
That can be a problem if you havesubclinical hypothyroidism.
It comes up whenever you have a mildly elevated TSH and normalfree T4, but no symptoms.
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Subclinical hypothyroidism may be missed if you take your test in the afternoon and you have not been fasting.
The evidence for the influence of these things is unclear.
Still, it is a good idea to have your thyroid levels checked under the same conditions each time.
This can help avoid false fluctuations on your test results.
Schedule your TSH tests for around the same time of day.
If you fasted for one test, fast for all of them.
They’re finding more nuances in how weight and body mass affect thyroid function.
Thyroid tests from people who quit smoking show their TSH goes up and the T4 goes down.
The reasons why smoking affects thyroid function remain under investigation.
Lower free T3 and free T4 levels also have been reported in people following theiralcohol withdrawal.
Medication Use and Thyroid Test Results
Certain medications can cause thyroid dysfunction.
These drugs can interfere with your thyroid hormone levels or with their action.
These include:
These may prevent you from getting enough of your medication into your system.
Thyroid Hormone Measurements
Other medications can interfere with thyroid lab measurements.
These drugs do not affect the actual functioning of the thyroid.
Certain drugs and supplements may interfere with your test results.
Some can change thyroid function or get in the way of your body’s ability to absorb thyroid medications.
Others may interfere with the test itself.
Thyroid Levels During Pregnancy
Thyroid hormone levels change during pregnancy.
In fact, the ranges considered normal also change throughout pregnancy.
What is considered normal may be slightly different depending on the lab where you get your blood test.
Thyroid levels are measured in milliunits per liter (mU/L) and picomoles per liter (pmol/L).
A mole is a way to measure large amounts of very small things like atoms and molecules.
A picomole is one trillionth of a mole.
Normal ranges for non-pregnant people are as follows:
Normal ranges for pregnant people are different.
Illness and Thyroid Test Results
Certain illnesses can temporarily affect thyroid hormone results.
Diarrhea can interfere with your medication absorption and may alter your lab results.
Infections or a bout of an inflammatory condition such aslupuscan also have an effect.
For that reason, people with this condition do not receive treatment to correct thyroid levels.
Summary
Outside factors may affect the results of your thyroid test.
Some medications and supplements may also affect your results.
This may be because they change your thyroid function.
It may also be because they reduce your body’s ability to absorb thyroid hormone.
Other drugs and supplements may just interfere with the test itself.
Pregnant people have different normal thyroid levels than those who are not pregnant.
Certain illnesses may also interfere with your results.
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