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

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

This test measures the amount of thyroid-stimulating hormone in your blood, which helps regulate your thyroid function.

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
27891-1
Short code
T4 BS SerPl-mCnc
Synonyms
T4 BS SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
4.5
Ref high
12
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84436
SNOMED
302345006
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 often the first test used to check thyroid health, especially if you have 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 fasting panel. Bring any medications you’re taking, as some (like thyroid hormone replacement) can affect results.

How the Test Works

A small blood sample is drawn from a vein in your arm. The blood is sent to a lab, where it’s analyzed to measure TSH levels. The test detects the hormone produced by your pituitary gland to signal your thyroid to produce hormones like thyroxine (T4).

What the Results Mean

Results are interpreted based on your symptoms and overall health. Low TSH levels may indicate an overactive thyroid, while high levels often suggest an underactive thyroid. Your doctor will compare your results to your baseline and any other tests they’ve ordered.

Reference range

Adult: 4.5-12.0 μg/dLN/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

Short name

TSH (Serum/Plasma)

Frequently asked questions

What Are Common Symptoms to Watch For?
Symptoms like unexplained weight changes, fatigue, depression, or changes in your menstrual cycle can signal thyroid issues. If you have a family history of thyroid disease or symptoms like hair loss or dry skin, your doctor may recommend this test.
How Often Should I Get This Test?
Your doctor will determine how often you need retests. For example, if you have hypothyroidism, you may need regular monitoring to adjust your medication. If you’re pregnant, TSH testing may be done more frequently due to hormonal changes.
Can I Take Anything Before the Test?
Avoid smoking or drinking alcohol 24 hours before the test. Some medications (like certain antidepressants or blood pressure drugs) can affect TSH levels, so always inform your doctor about all medications you’re taking.
  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