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Thyroid Stimulating Hormone (TSH) with Immunoassay Method (Serum/Plasma)

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

This test measures the amount of thyroid-stimulating hormone (TSH) in your blood. TSH helps regulate your thyroid hormone levels, which are important for metabolism, energy, and overall health.

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
63360-2
Short code
Thyroglob Ab CSF IA-aCnc
Synonyms
Thyroglob Ab CSF IA-aCnc
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
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 used to check thyroid function, especially if you have symptoms like fatigue, weight changes, or unexplained mood swings.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood. If you’re taking thyroid medication, let your doctor know beforehand so they can adjust timing if needed.

What the Results Mean

TSH results help guide treatment. Low TSH might suggest hyperthyroidism, while high TSH often points to hypothyroidism. Your doctor will interpret results in the context of your symptoms and other tests.

Common Conditions This Test Helps Diagnose

This test is commonly used to diagnose or manage conditions like Hashimoto’s disease (autoimmune hypothyroidism), Graves’ disease (autoimmune hyperthyroidism), and thyroid nodules. It can also help monitor thyroid replacement therapy.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

TSH Level

Frequently asked questions

Why might my TSH test be done even if I don’t have symptoms?
Your doctor may order it as part of a routine checkup, especially if you’re at higher risk for thyroid issues (e.g., family history, age, or certain medical conditions). It’s also used to monitor thyroid treatments or screen for conditions like pregnancy-related thyroid problems.
What if my TSH is outside the normal range?
If your TSH is high, it may indicate an underactive thyroid, while a low TSH could suggest an overactive thyroid. Your doctor will discuss next steps, such as additional tests or treatment adjustments, based on your results and symptoms.
Can I eat or drink anything before this test?
You can eat and drink normally before the test unless your doctor specifies otherwise. Some tests may require fasting, but TSH tests do not.
  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