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Thyroid Stimulating Hormone (TSH) – Serum

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

This test measures the amount of thyroid-stimulating hormone in your blood. TSH helps regulate your thyroid gland, which produces hormones that control metabolism, energy levels, and other important body functions.

Quick summary

["Your TSH level 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
77653-4
Short code
Thin Prep Anorectl
Synonyms
Thin Prep Anorectl
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
cyto-stain-thin-prep
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 This Test Is Done

Doctors may order a TSH test to diagnose or monitor thyroid conditions, such as hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid). It’s also used to check for thyroid cancer or other thyroid-related issues. Sometimes, it’s part of routine health checks, especially in older adults or those with symptoms like fatigue, weight changes, or unexplained mood swings.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a broader metabolic panel. Bring any medications you’re taking, as some (like certain thyroid medications) can affect results.

How the Test Is Done

A small blood sample is drawn from a vein in your arm, typically in a doctor’s office or lab. The blood is sent to a lab where it’s analyzed to measure TSH levels.

What the Results Mean

Results are reported in international units per liter (IU/L). High TSH levels often indicate hypothyroidism, while very low levels may suggest hyperthyroidism. Your doctor will interpret results in relation to your symptoms and medical history.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

TSH Level

Frequently asked questions

What could cause abnormal TSH levels?
Abnormal TSH levels can be caused by thyroid disorders (e.g., Hashimoto’s disease, Graves’ disease), pituitary gland issues, pregnancy, certain medications (like lithium or amiodarone), or thyroid surgery/radiation treatment. Always discuss symptoms and results with your healthcare provider.
How often should I get this test?
Frequency depends on your health status. If you have a thyroid condition, your doctor may recommend regular monitoring. Otherwise, it’s often checked only when symptoms or risk factors (like family history) suggest it’s needed.
Can I eat or drink before this test?
Typically, fasting is required for 8–12 hours before the test if it’s part of a metabolic panel. For a standalone TSH test, no fasting is usually needed, but always follow your doctor’s instructions.
  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