Quick Facts
- Sample: 4 mL blood in lavender-top EDTA tube
- Fasting: No fasting required
- Turn-around: 6-8 business days. May take longer based on weather, holiday or lab delays.
Benefits
- Identify cancer-related hypercalcemia - Two-thirds of cancer patients with high calcium have elevated PTH-rP (Mayo Clinic 2025).
- Convenient direct access - Order without specialist referral for faster diagnosis.
- Differentiate hypercalcemia causes - Distinguish malignancy from primary hyperparathyroidism.
- Early intervention - Prevent complications like kidney failure and cardiac issues.
- No special preparation - Simple blood draw with no fasting required.
Who Is This Test For?
- Individuals with unexplained high calcium levels on routine blood work.
- People experiencing hypercalcemia symptoms like fatigue, muscle weakness, bone pain.
- Cancer patients being monitored for humoral hypercalcemia of malignancy.
- Those with kidney disease or suspected hyperparathyroidism.
- Patients with symptoms like nausea, confusion, frequent urination
How It Works - Just 3 Steps
- Order online - No doctor's visit needed; simply purchase your test
- Visit lab - Quick blood draw at any participating lab location
- Get results - Receive confidential results within 6-8 business days.
FAQ
What does this test measure? PTH-rP hormone levels in your blood to help diagnose the cause of high calcium levels.
How accurate is this test? Highly accurate - 50-70% of cancer patients with hypercalcemia show elevated PTH-rP (Mayo Clinic 2025).
Can this test detect cancer? It identifies cancer-related hypercalcemia but isn't a cancer screening test - results need clinical context.
What if my results are abnormal? Consult a healthcare provider immediately; further imaging or oncology referral may be needed.
How quickly will I get results? Results typically available within 6-8 business days depending on lab processing time.
More Details
What is the purpose of this test?
The PTH-rP Plasma Test measures parathyroid hormone-related peptide levels to investigate abnormally high blood calcium (hypercalcemia). PTH-rP is a protein that regulates calcium, phosphorus, and vitamin D balance. This test primarily helps differentiate hypercalcemia caused by cancer from other causes like primary hyperparathyroidism (UCSF Health 2023).
Who would benefit from this test?
Health-conscious individuals using direct-to-consumer lab services benefit from convenient assessment of unexplained hypercalcemia without initial specialist referral. Early PTH-rP detection prompts timely evaluation for underlying cancers or parathyroid disorders. The test supports proactive management of calcium metabolism disorders linked to osteoporosis, kidney stones, and heart disease (Mount Sinai 2023).
When should I order this test?
Order this test when experiencing hypercalcemia symptoms including nausea, fatigue, muscle weakness, bone pain, confusion, increased thirst, or frequent urination. It's also appropriate when routine blood tests show elevated calcium levels requiring further investigation, or for monitoring patients with known malignancies at risk for humoral hypercalcemia.
How do I interpret the results?
PTH-rP Level: ≤4.2 pmol/L (Normal)
- What it means: No evidence of PTH-rP excess
- Typical action: Investigate other hypercalcemia causes
PTH-rP Level: >4.2 pmol/L (Elevated)
- What it means: Suggests malignancy-related hypercalcemia
- Typical action: Urgent oncology evaluation needed
PTH-rP Elevated + High Calcium
- What it means: Likely humoral hypercalcemia of malignancy
- Typical action: Immediate specialist referral
Normal PTH-rP with high calcium typically suggests primary hyperparathyroidism or vitamin D disorders rather than malignancy.
Disclaimer: Reference ranges may vary by laboratory. Listed ranges are general guidelines and may differ from those used by the performing lab. Always consult your healthcare provider for interpretation
Pre-test preparation
No fasting or medication adjustments typically required. Inform your provider if breastfeeding, as this may affect results. Stay well-hydrated before your blood draw. The sample requires special handling - immediate chilling and plasma separation with frozen storage.
How often should I get tested?
- Initial hypercalcemia evaluation: One-time test with clinical correlation
- Known cancer with hypercalcemia risk: As directed by oncologist
- Monitoring treatment response: Every 3–6 months or as clinically indicated
- Unexplained symptoms: Single test, repeat if symptoms persist
Why early detection matters
Hypercalcemia affects 10-20% of cancer patients and often indicates advanced disease. Early PTH-rP detection enables prompt treatment, preventing serious complications including kidney failure, cardiac arrhythmias, and bone disease. Timely intervention reduces healthcare costs and significantly improves quality of life for patients with calcium metabolism disorders (Ashrafzadeh-Kian et al. 2022).
Related tests you may consider
Calcium Ionized Serum Test - Measures ionized calcium levels in the blood to help screen for, diagnose, and monitor various conditions related to the bones, heart, nerves, kidneys, and teeth.
Parathyroid Hormone (PTH) Blood Test Plus Calcium- Measures PTH and calcium levels to check for parathyroid disorders, helping diagnose issues like hyperparathyroidism or osteoporosis that can affect bone strength, kidney function, and overall health.
Vitamin D 25-Hydroxy Blood Test - Checks if you have enough vitamin D, helping to ensure your bones stay healthy and reducing the risk of various health issues associated with vitamin D deficiency.
Comprehensive Metabolic Panel (CMP-14) with eGFR Blood Test - Evaluates nutrient levels, liver, and kidney function.
