Is fasting required for a hypothyroidism check-up?
Jul 21, 2025
Source: Cainiu Health
Dr. Yang Chuanjia
Introduction
The primary test for hypothyroidism refers to thyroid function tests. Generally, a simple thyroid function test does not require fasting. However, if other tests that require fasting, such as liver function tests or blood glucose tests, are also needed at the same time, then fasting will be required. If you have any questions regarding the test requirements, it is recommended to consult the hospital beforehand. Prior to the test, maintain normal eating habits and regular作息 (作息 should be translated as "作息" → "作息" means rest and activity patterns, so better translation would be "maintain normal eating habits and regular daily routines").
Hypothyroidism examination mainly refers to thyroid function tests. Generally, a simple thyroid function test does not require fasting. However, if other tests requiring fasting, such as liver function tests or blood glucose tests, are also needed, fasting is necessary. If you have any questions about the testing requirements, it is recommended to consult the hospital beforehand. Detailed explanation is as follows:
The core examination for hypothyroidism involves thyroid function indicators, such as thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4). The results of these indicators are generally not affected by food intake. After eating, the levels of thyroid hormones in the blood do not fluctuate significantly; therefore, when conducting only a thyroid function test, fasting is not required, and blood can be drawn at any time of the day.
If additional blood tests such as liver function, lipid profile, or blood glucose are also required during the examination, fasting is necessary because food intake can affect the accuracy of these indicators. For example, blood glucose levels rise and lipid levels fluctuate after eating, so an 8-12 hour fast is generally recommended. In such cases, the "fasting" requirement should be followed to ensure the reliability of all test results.
Before the examination, maintain normal eating habits and作息 (sleep-wake cycle), and avoid heavy alcohol consumption or eating excessively greasy food the night before, to prevent interference with other concurrent tests. If you are taking thyroid hormone medications, there is no need to discontinue them. You can take your medication as usual before the examination, but be sure to inform your doctor about your medication use in advance.
