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Thyroid Stimulating Hormone (TSH) - Serum

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

This blood test measures your thyroid-stimulating hormone, a key hormone that helps regulate your metabolism and thyroid function. It’s often used to check for thyroid disorders.

Quick summary

["TSH helps diagnose thyroid problems, including underactive (hypothyroidism) or overactive (hyperthyroidism) thyroid conditions."]

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

Key facts at a glance

LOINC
54219-1
Short code
TT imm 1:4 NP PPP
Synonyms
TT imm 1:4 NP PPP
Category
chemistry
Sample
plasma
Container
Lavender-top (EDTA) or Green-top (Heparin)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
coag-thrombin-induced-factor-substitution-immediately-after-addition-of-normal-plasma
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

What Is TSH Used For?

TSH is primarily used to screen for and monitor thyroid disorders. It can help identify whether your thyroid isn’t producing enough hormone (hypothyroidism) or too much (hyperthyroidism). Doctors may also use it to check for thyroid-related issues during pregnancy or after treatment for thyroid cancer.

How Is TSH Tested?

A small blood sample is taken from your arm and sent to a lab. The test measures the amount of TSH in your serum, which is the liquid part of your blood after red blood cells and clotting factors are removed.

What Might Affect TSH Results?

Several factors can influence TSH levels, including stress, certain medications (like thyroid hormone medications or antidepressants), pregnancy, and thyroid-related conditions. Some medical conditions, such as pituitary disorders, can also affect TSH.

Common Reasons for a TSH Test

Your doctor may order a TSH test if you have symptoms like fatigue, weight changes, unexplained hair loss, or mood swings. It’s also used as part of routine check-ups, especially for people at higher risk of thyroid issues.

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 during pregnancy?
TSH tests are commonly checked during pregnancy to screen for thyroid disorders, as thyroid hormone levels play a crucial role in fetal development. Thyroid issues in pregnancy can affect both mother and baby.
What are the typical symptoms that might lead to a TSH test?
Symptoms like unexplained weight changes, fatigue, frequent colds, dry skin, or mood swings—such as depression or irritability—may prompt a TSH test. If you notice these symptoms, talk to your doctor.
How soon will I get my TSH test results?
Results are usually available within a few days to a week, depending on your lab and healthcare provider. Your doctor will discuss the findings with you and explain next steps.
  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