Skip to content

Thyroid Stimulating Hormone (TSH) with Serum/plasma Specimen

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

This blood test measures the amount of thyroid-stimulating hormone (TSH) in your blood. TSH helps regulate your thyroid hormone levels, which control metabolism, energy, and overall health.

Quick summary

["TSH 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
12948-6
Short code
TSH sp9 p chal SerPl-aCnc
Synonyms
TSH sp9 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 diagnose or monitor thyroid conditions, such as hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid). It’s also used to screen for thyroid issues, especially in people with symptoms like fatigue, weight changes, or unexplained mood swings.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a metabolic panel. Wear comfortable clothing for a simple blood draw, usually taken from your arm.

What Happens During the Test?

A healthcare professional will clean your arm, insert a small needle to draw blood, and collect it in a tube. The process takes just a few minutes, and you may feel a brief pinch. The blood is then sent to a lab for analysis.

What the Results Mean

Results help determine if your thyroid hormone levels are within normal range. Abnormally high or low TSH can signal thyroid dysfunction, but interpretation depends on your overall health and symptoms.

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.

Clinical Significance: TSH Testing

Short name

TSH Level

Frequently asked questions

What are the typical reference ranges for this test?
Reference ranges vary by lab and individual factors like age, sex, and health status. Your doctor will review your results in the context of your medical history and symptoms. If results are outside normal limits, further testing (e.g., free T4) may be needed to clarify the cause.
Will I need to take any medications before or after this test?
Some medications, like thyroid hormone replacement drugs, can affect TSH levels. If you’re on medication, inform your doctor before the test. They may adjust timing or instructions. Avoid taking thyroid medications 24 hours before the test if possible.
Can I eat or drink anything before this test?
For fasting tests, avoid food and liquids (except water) for 8–12 hours before drawing blood. If your doctor doesn’t specify, you can eat normally. Always follow their exact instructions to ensure accurate 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