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Parathyroid Hormone (PTH) by Immunoassay (Serum/Plasma)

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

This test measures the level of parathyroid hormone (PTH), a key hormone that helps regulate calcium and phosphate levels in your blood.

Quick summary

["PTH helps maintain healthy bone and mineral balance in your body."]

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

Key facts at a glance

LOINC
40304-8
Short code
GH 1.5h p Arg SerPl-mCnc
Synonyms
GH 1.5h p Arg SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 Parathyroid Hormone (PTH)?

PTH is produced by the parathyroid glands, small glands located near your thyroid. It plays a critical role in managing calcium and phosphate, which are essential for strong bones, muscle function, and nerve signaling. When your blood calcium levels drop, PTH signals your body to release calcium from bones or absorb it from your intestines.

Why Might You Need This Test?

Your doctor may order a PTH test to check for conditions like hypoparathyroidism (low PTH), hyperparathyroidism (high PTH), or to monitor treatment for conditions affecting calcium levels, such as kidney disease or osteoporosis.

Common Reasons for Testing

Common reasons include diagnosing or managing disorders related to calcium metabolism, evaluating symptoms like muscle weakness, bone pain, or frequent fractures, or checking for complications from certain medications or medical conditions.

Sample Collection and Preparation

A blood sample is taken from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause significant discomfort. The sample is sent to a lab for testing using an immunoassay method to detect PTH levels in your serum or plasma.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

PTH (Serum/Plasma)

Frequently asked questions

Low PTH levels may indicate hypoparathyroidism, which can lead to symptoms like muscle spasms, numbness, or irregular heartbeat. High PTH levels might suggest hyperparathyroidism, which can cause bone weakness, kidney stones, or high blood calcium levels.
What does a PTH test measure?
A PTH test measures the amount of parathyroid hormone in your blood. This hormone helps regulate calcium and phosphate, which are vital for maintaining healthy bones, muscles, and nerves.
How long does it take to get results?
Results from a PTH test are typically available within 1 to 3 business days, depending on your lab’s processing time.
You can usually eat and drink normally before the test unless your doctor specifies otherwise. However, avoid caffeine or large amounts of calcium-rich foods for a few hours before the test if instructed.
  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