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Thyroid Stimulating Hormone (TSH) - Serum

Published: August 9, 2026Updated: August 16, 2026

This blood test measures the level of thyroid-stimulating hormone (TSH) in your serum. TSH helps regulate your thyroid gland’s production of hormones that control metabolism.

Quick summary

["TSH helps doctors check if your thyroid is working properly."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
69101-4
Short code
Deprecated CT Thyroid Bx needle guide
Synonyms
Deprecated CT Thyroid Bx needle guide
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ct
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order a TSH test to diagnose or monitor thyroid conditions, such as hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid). It’s often the first test for thyroid issues because it’s highly sensitive.

What to Expect Before the Test

No special preparation is needed for this test. You may have a small needle inserted into your arm or hand to draw blood. If you’re on certain medications that affect thyroid function, let your doctor know before the test.

What Happens During the Test?

A healthcare professional will collect a small sample of blood from a vein in your arm. The sample is sent to a lab for analysis. Results are typically available within a few days.

What Do the Results Mean?

TSH levels can vary based on your health and medical history. High TSH levels may suggest hypothyroidism, while very low levels may indicate hyperthyroidism. Your doctor will interpret results in the context of your overall health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: TSH plays a critical role in thyroid hormone regulation. Abnormal levels can signal underlying thyroid disorders, which may require treatment like medication, lifestyle changes, or further testing.

Short name

TSH Test

Frequently asked questions

How often should I get a TSH test?
Your doctor will determine how often you need a TSH test based on your medical history, symptoms, and treatment plan. Regular monitoring may be needed if you have a thyroid condition or take thyroid medications.
What are common symptoms of thyroid issues that might lead to a TSH test?
Symptoms like fatigue, weight changes, unexplained hair loss, or mood swings could indicate thyroid problems. If you experience these symptoms, your doctor may recommend a TSH test or other thyroid-related tests.
Can diet affect TSH test results?
Yes, certain foods and supplements, such as soy products, iodine-rich foods, or selenium, can temporarily affect thyroid function. Avoiding large doses of these for a few weeks before your test may help ensure more accurate results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy