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Thyroid Stimulating Hormone (TSH) with Serum/Plasma Concentration Measurement

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 gland’s activity, which affects metabolism, energy levels, and overall health.

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
12941-1
Short code
TSH sp2 p chal SerPl-aCnc
Synonyms
TSH sp2 p chal SerPl-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.4
Ref high
4
Critical range
0.1 N/A – 20 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84443
SNOMED
301343003
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 check for thyroid issues, especially if you have symptoms like fatigue, weight changes, or unexplained mood swings. It’s often the first test for thyroid disorders due to its sensitivity.

What to Expect Before the Test

No special preparation is needed, but you may fast for 8–12 hours before the draw if instructed. Bring your lab results and current medications to your appointment.

What Happens During the Test?

A healthcare provider will collect a blood sample from a vein in your arm. The sample is sent to a lab for analysis using an immunoassay method to measure TSH levels.

What Do Results Mean?

Results help determine if your thyroid is functioning normally. Abnormally high or low TSH levels may signal thyroid problems that need further evaluation.

Reference range

Adult: 0.4-4.0 mIU/LN/A

Specimen: serum

Take your thyroid medication after the blood draw if applicable. No fasting required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

TSH Level

Frequently asked questions

What causes abnormal TSH results?
Abnormal TSH levels can result from thyroid diseases (e.g., Hashimoto’s thyroiditis, Graves’ disease), pituitary disorders, or medications that affect thyroid function. Other causes may include pregnancy, thyroid surgery, or radiation treatment.
How often should I get this test?
Your doctor will determine how often you need retesting based on your symptoms, medical history, and treatment plan. Regular follow-ups may be recommended if you have a thyroid condition.
Can lifestyle changes affect TSH results?
Yes, stress, poor sleep, and certain medications (e.g., lithium, amiodarone) can influence TSH levels. Avoiding these factors before testing may improve accuracy.
  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