Parathyroid hormone (PTH) blood test

Parathyroid Hormone (PTH) Blood Test

A parathyroid hormone (PTH) blood test is a type of endocrine test that examines the presence, quantity, and activity level of parathyroid hormone in a person's bloodstream. It is used as a diagnostic tool to detect and diagnose an excess or deficiency in the parathyroid gland. It can also help determine possible causes of diseases related to bone and calcium metabolism, such as hypercalcemia and hypocalcemia.


Before the parathyroid hormone (PTH) blood test, your doctor will likely recommend that you avoid any medications or dietary supplements that contain calcium, including calcium supplements and vitamin D, for up to one week prior to the test. You should also fast for eight to 12 hours before the test.


The parathyroid hormone (PTH) blood test is performed in a doctor's office or a laboratory using a standard blood sample taken from a vein in your arm. The blood sample will then be sent to a lab for analysis.


The parathyroid hormone (PTH) blood test can measure three different types of PTH:

  • Intact, or total PTH, measures the sum of active and inactive PTH.
  • Active PTH measures only the active and functioning form of PTH.
  • Propeptide PTH measures the amount of PTH that is inactive.


The risks of the parathyroid hormone (PTH) blood test are minimal. The most common side effects are slight pain and bruising at the site where the needle was inserted to draw blood. This can usually be minimized by applying pressure to the area after the needle is removed.

Why it's done

The parathyroid hormone (PTH) blood test is used to diagnose and monitor conditions that can affect the parathyroid gland, including hyperparathyroidism, hypoparathyroidism, and cancerous or benign (noncancerous) tumors of the parathyroid gland. It may also be used to monitor the effectiveness of treatment for these conditions.

When it's done

The parathyroid hormone (PTH) blood test may be done at any point in time, although it is usually done along with other blood tests to measure levels of calcium, phosphorus, and other hormones. It can also be done at regular intervals to monitor the effectiveness of treatment.