Parathyroid Hormone (Active), Serum/Plasma
This test measures the active form of parathyroid hormone (PTH), a key hormone that helps regulate calcium levels in your body.
["Active PTH helps your body maintain healthy calcium and bone balance."]
Key facts at a glance
- LOINC
- 2731-8
- Short code
- PTH-Intact SerPl-mCnc
- Synonyms
- PTH-Intact 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 Is This Test Done?
Your doctor may order this test to evaluate conditions affecting calcium metabolism, such as hypoparathyroidism (low PTH), hyperparathyroidism (high PTH), or kidney disease. It can also help diagnose or monitor bone diseases, vitamin D deficiency, or metabolic bone disorders.
What Does It Measure?
Active PTH is the biologically active fragment of the full hormone, which directly influences calcium and phosphate levels in your blood. This version is more accurate for assessing your body’s response to calcium imbalances than the full PTH form.
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 your blood is drawn in the morning. Wear comfortable clothing and arrange for someone to drive you home if you’ve had alcohol or certain medications.
What Happens During the Test?
A healthcare provider will insert a small needle into a vein in your arm, draw a blood sample, and apply pressure to stop bleeding. The sample is sent to a lab for analysis using an immunoassay method to detect the active PTH levels.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
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.
Low active PTH levels may indicate hypoparathyroidism, which can cause muscle cramps, numbness, or irregular heart rhythms. High levels may suggest hyperparathyroidism, leading to bone weakness, kidney stones, or fatigue. Monitoring active PTH helps guide treatment for conditions like vitamin D deficiency or metabolic bone diseases.
Short name
Active PTH
Frequently asked questions
What does an abnormal result mean?
How long will it take to get my results?
Can I eat or drink before this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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