Skip to content

Thyroid Stimulating Hormone (TSH) with Serum/Plasma Measurement

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

This test measures the amount of thyroid-stimulating hormone (TSH) in your blood, which helps your thyroid gland produce hormones that regulate metabolism.

Quick summary

["TSH helps diagnose thyroid disorders and monitor treatment for conditions like hypothyroidism or hyperthyroidism."]

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

Key facts at a glance

LOINC
12933-8
Short code
TSH 10M p chal SerPl-aCnc
Synonyms
TSH 10M 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

What Is TSH Used For?

TSH is primarily used to check if your thyroid is working properly. Low or high levels can signal conditions such as underactive (hypothyroidism) or overactive (hyperthyroidism) thyroid function. It’s often the first test recommended for thyroid-related symptoms like fatigue, weight changes, or unexplained mood swings.

How Is the Test Performed?

A small blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed using an immunoassay method to measure TSH levels accurately.

Preparation and Timing

No special preparation is needed for this test. You can eat, drink, or take medications as usual. Some tests may require fasting, but TSH is not affected by food or recent meals.

What Might Affect Results?

Several factors can influence TSH levels, including pregnancy, certain medications (like those for thyroid disorders or depression), stress, or sleep patterns. If you’re taking medications, inform your healthcare provider before the test.

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.

Abnormal TSH levels can indicate underlying thyroid disorders. Low TSH may suggest hypothyroidism, while high TSH can signal hyperthyroidism or other conditions like pituitary issues. Regular monitoring with TSH is essential for managing thyroid health, especially if you have a history of thyroid problems or symptoms like fatigue, weight gain, or depression.

Short name

TSH Level

Frequently asked questions

Why might my TSH test be done?
Your doctor may order a TSH test to check for thyroid problems, monitor an existing thyroid condition, or evaluate symptoms like fatigue, weight changes, or hair loss that could be linked to thyroid dysfunction.
What do TSH results mean?
Results are interpreted by your healthcare provider based on your overall health and symptoms. Low TSH might mean your thyroid isn’t producing enough hormones, while high TSH could suggest overactivity or other issues. No single range applies universally—your doctor will discuss what’s normal for you.
Can TSH levels change over time?
Yes, TSH levels can fluctuate due to factors like stress, illness, or hormonal changes. If you have a thyroid condition, your doctor may recommend periodic testing to track progress with treatment or monitor for changes in your health.
  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