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Parathyroid Hormone (PTH) Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Parathyroid Hormone (PTH) Test

A parathyroid hormone (PTH) test measures the level of PTH in your blood to help determine if your parathyroid glands are functioning correctly to regulate calcium levels.

What is a parathyroid hormone (PTH) test?

This test measures the level of parathyroid hormone (PTH) in your blood. PTH is produced by your parathyroid glands, which are four pea-sized glands located in your neck. Hormones act as chemical messengers in your bloodstream, controlling the actions of certain cells or organs. PTH specifically controls the level of calcium in your blood, which is essential for the proper function of your nerves, muscles, and heart.

When blood calcium levels are low, your parathyroid glands release PTH to restore balance by:

  • Telling your bones to release calcium into your blood.
  • Helping your intestines absorb calcium from food.
  • Helping your kidneys retain calcium instead of excreting it through urine.

When calcium levels return to normal, the glands stop producing PTH. Because PTH levels fluctuate based on calcium levels, providers often order a calcium blood test alongside a PTH test to assess gland function.

What is it used for?

A PTH test is used to:

  • Identify if parathyroid disorders are causing abnormal blood calcium levels.
  • Determine the cause of abnormally low results on a phosphate blood test.
  • Monitor individuals with chronic kidney disease.
  • Investigate the cause of severe osteoporosis.
  • Evaluate the effectiveness of treatment for a known parathyroid disorder.
  • Verify if all overactive parathyroid tissue was removed during surgery.

Why do I need a PTH test?

You may need this test if you have abnormal calcium levels or symptoms of a parathyroid disorder. Symptoms of high calcium (hypercalcemia) may include:

  • Digestive issues: constipation, nausea, vomiting, abdominal pain, or loss of appetite.
  • Increased thirst and frequent urination.
  • Kidney stones.
  • Bone, joint, and muscle weakness or pain.
  • Fatigue.
  • Mental health changes, such as confusion or depression.

Symptoms of low calcium (hypocalcemia) may include:

  • Dry skin, coarse hair, and brittle nails.
  • Muscle cramps, spasms, or stiffness.
  • Tingling in the lips, tongue, fingers, and feet.
  • Irregular heartbeat (arrhythmia).
  • Seizures (in severe cases).

What happens during a PTH test?

A health care professional will collect a blood sample from a vein in your arm using a small needle. The process typically takes less than five minutes.

What do the results mean?

Providers interpret PTH levels in the context of blood calcium and other medical history.

High PTH (Hyperparathyroidism)

  • Primary hyperparathyroidism: High PTH with high blood calcium. Often caused by a benign tumor (parathyroid adenoma), gland enlargement (hyperplasia), rare inherited conditions, or, rarely, cancer.
  • Secondary hyperparathyroidism: High PTH with low blood calcium. The glands are working correctly to compensate for an external issue, such as vitamin D deficiency, magnesium deficiency, digestive malabsorption, or kidney failure.

Low PTH (Hypoparathyroidism)

Low PTH with low blood calcium indicates the glands cannot produce enough hormone. Causes include:

  • Damage from neck surgery or radiation therapy.
  • Autoimmune disorders.
  • Genetic disorders, such as DiGeorge syndrome.
  • Excessive intake of vitamin D or calcium.
  • Serious illnesses.

Frequently Asked Questions

PTH levels can fluctuate with recent meals, especially calcium‑rich foods, and with certain medications such as vitamin D supplements, thiazide diuretics, or calcium‑based antacids. To obtain the most accurate reading, avoid large calcium or vitamin D doses for 24–48 hours before the test, and inform your clinician of all medications and supplements you are taking. If you have a history of kidney disease, fasting is usually recommended, but confirm with your provider.
high PTH with normal calcium can indicate secondary hyperparathyroidism, commonly seen in early kidney disease or vitamin D deficiency. It may also reflect a mild primary hyperparathyroidism where calcium is still within normal limits. Your clinician will likely repeat the calcium and PTH, check vitamin D levels, and possibly perform imaging of the parathyroid glands to determine the underlying cause.
fter parathyroidectomy, PTH levels typically fall within minutes. Your surgeon will usually check a “rapid” intra‑operative PTH to confirm removal of all overactive tissue. Post‑operatively, a repeat PTH and calcium are often done 24–48 hours later. Long‑term monitoring is usually every 6–12 months, or sooner if you develop symptoms of hypocalcemia or if calcium levels rise again. Follow your surgeon’s schedule for follow‑up testing.
Patients with chronic kidney disease often have altered calcium and phosphate metabolism, which can influence PTH. Your clinician may order a fasting calcium, phosphate, and PTH panel together. Avoid high‑phosphate foods (e.g., dairy, nuts) for 12–24 hours before the test, and continue any prescribed phosphate binders as directed. Discuss whether to fast or not, as some labs allow non‑fasting samples for PTH.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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