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Parathyroid Hormone (Active) - Serum

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

This test measures your active form of parathyroid hormone (PTH), a key hormone that helps regulate calcium levels in your blood. It’s important for bone health and nerve function.

Quick summary

["Active PTH helps balance calcium, supporting bone strength and preventing complications like abnormal heart rhythms or muscle weakness."]

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

Key facts at a glance

LOINC
16164-6
Short code
PTH-Intact 2h p chal SerPl-mCnc
Synonyms
PTH-Intact 2h p chal SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85610
SNOMED
396252006
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 This Test Is Done

Your doctor may order an active PTH test if you have symptoms like bone pain, frequent fractures, or unexplained high or low calcium levels. It’s also used to monitor conditions like hyperparathyroidism or kidney disease that affect calcium metabolism.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, usually drawn from your arm. If you’re on certain medications (like calcium supplements or vitamin D), let your doctor know beforehand.

What the Results Mean

Results help determine if your calcium levels are balanced. High levels may indicate overactive parathyroid glands, while low levels could suggest other health issues like kidney disease or vitamin D deficiency.

Common Conditions Affecting Results

Conditions like chronic kidney disease, vitamin D deficiency, or certain cancers can alter PTH levels. Your doctor will consider your full medical picture when interpreting results.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: serum

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Active PTH

Frequently asked questions

What causes false high or low results?
False high results may occur if you’ve recently eaten calcium-rich foods, had recent trauma, or are on certain medications. False low results can happen with lab errors or if the test was done too soon after a blood draw.
How long do I need to wait for results?
Results are typically available within 1–3 business days, depending on your lab. Your doctor will contact you once they’re ready.
Can I eat or drink before this test?
Yes, you can eat and drink normally. Avoid calcium supplements or high-calcium foods for 24 hours before testing if instructed by your doctor.
  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