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Serum or plasma parathyroid hormone (PTH) measured by chemiluminescent immunoassay (CLIA)

Published: August 9, 2026Updated: August 15, 2026

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

Quick summary

["PTH helps balance calcium, which is important for bone health and nerve function."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
12506-2
Short code
CALCITON2
Synonyms
Calcit sp2 p chal SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top serum separator tube (SST) or plain red-top tube; alternatively, lavender-top (EDTA) plasma tube.
Units
N/A
Ref low
0
Ref high
10
Critical range
— – 1000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
Immunoassay (Chemiluminescent Immunoassay / CLIA or Radioimmunoassay / RIA)
CPT
82308
SNOMED
39514009
Specimen volume
1-2 mL serum or plasma per specimen; minimum 0.5 mL required for analysis. For complete stimulation testing, multiple specimens (baseline + post-stimulation) totaling 3-5 mL may be required.
Stability
Serum/plasma stable for 4 hours at room temperature (15-25°C), 24 hours refrigerated at 2-8°C, and up to 30 days frozen at -20°C or below. Avoid repeated freeze-thaw cycles. Centrifuge within 2 hours of collection.
Hemolysis max
100
Lipemia max
100
Icterus max
50
TAT
24–72 hours
Order
routine

What Is PTH Used For?

PTH is primarily used to diagnose and monitor conditions affecting calcium metabolism, such as hypoparathyroidism (low PTH) or hyperparathyroidism (high PTH). It can also help assess kidney function and bone health.

Why Might You Need This Test?

Your doctor may order this test if you have symptoms like muscle cramps, frequent bone fractures, or abnormal calcium levels. It’s also used in cases of suspected thyroid or kidney disorders.

How Is the Test Performed?

A blood sample is taken from a vein in your arm. The sample is sent to a lab where it’s analyzed using a sensitive immunoassay method to detect PTH levels.

What Are Common Conditions Linked to PTH?

High PTH levels may indicate overactive parathyroid glands, while low levels can signal problems like hypoparathyroidism or vitamin D deficiency.

Reference range

Reference ranges for calcitonin post-stimulation challenge vary by laboratory and assay method. Peak stimulated calcitonin levels are evaluated against sex-specific thresholds. Typical interpretive guidelines: Baseline normal <10 pg/mL (males) and <5 pg/mL (females). Pentagastrin-stimulated peak: normal <100 pg/mL (males) and <50 pg/mL (females). Calcium-stimulated peak: normal <150 pg/mL. Values exceeding these thresholds may suggest medullary thyroid carcinoma (MTC) or C-cell hyperplasia.N/A

Specimen: serum

No fasting required. Patient should be in supine position for at least 15 minutes prior to blood draw. Stimulation agent (pentagastrin 0.5 mcg/kg IV or calcium gluconate 2 mg/kg IV) administered as ordered by physician. Second specimen collected 2 minutes post-stimulation (pentagastrin) or 5-10 minutes post-stimulation (calcium gluconate). Discontinue biotin supplementation at least 72 hours prior to testing as biotin may interfere with immunoassay results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

PTH plays a critical role in maintaining calcium balance. Abnormal levels can lead to complications like bone disease, kidney stones, or muscle weakness. Your doctor will interpret results in the context of your symptoms and medical history.

Short name

PTH (Serum/Plasma)

Frequently asked questions

What does a high PTH level mean?
A high PTH level may suggest overactive parathyroid glands, kidney disease, or vitamin D deficiency. Your doctor will review your results with other tests and symptoms to determine the cause.
What does a low PTH level mean?
A low PTH level may indicate hypoparathyroidism, thyroid disorders, or certain medications that affect calcium metabolism. Further testing may be needed to identify the exact cause.
How often should I get this test?
The frequency depends on your health condition. If you have a known disorder like hyperparathyroidism, your doctor may recommend regular monitoring. If this is a one-time test, follow-up will be guided by your symptoms and test 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 15, 2026. · Read our editorial policy