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Thyroid Stimulating Hormone (TSH) with Radioimmunoassay (RIA) or Related Method

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

This test measures your thyroid-stimulating hormone, a key hormone that helps regulate your thyroid’s activity. It’s often used to check for thyroid disorders like hypothyroidism or hyperthyroidism.

Quick summary

["A TSH test helps diagnose and monitor thyroid function, ensuring your body’s metabolism stays balanced."]

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

Key facts at a glance

LOINC
69129-5
Short code
RF Guided Thyroid Bx
Synonyms
RF Guided Thyroid Bx
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
rf
CPT
86430
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 if you have symptoms like fatigue, weight changes, or unexplained issues with your heart, digestion, or mood. It’s also used during pregnancy, before thyroid surgery, or when other thyroid tests are needed for confirmation.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the blood draw if your lab uses a specific protocol. Wear a loose shirt for easy access.

How the Test Works

A small sample of blood is taken from a vein in your arm. The sample is sent to a lab where it’s analyzed to measure TSH levels. The result helps determine whether your thyroid is working too slowly or too quickly.

What the Results Mean

Results are compared to a general range of normal values, but your doctor will interpret them in the context of your symptoms and medical history. Very high or very low TSH levels may signal thyroid issues that need further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

TSH Level

Frequently asked questions

What Are Common Symptoms to Watch For?
Symptoms like unexplained weight changes, fatigue, frequent colds, or changes in hair or skin texture can signal thyroid problems. If you notice these, mention them to your doctor, as TSH testing may be part of the evaluation.
How Often Should I Get This Test?
Your doctor will decide how often to repeat the test based on your health status. For example, if you have a diagnosed thyroid condition, follow-up tests may be scheduled every few months or annually.
Can Diet or Supplements Affect My TSH Test?
Yes, certain foods (like soy products in large amounts) or supplements (such as selenium or iodine) may influence thyroid function. Avoid taking excessive amounts of these unless approved by your doctor, as they can interfere with test 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