Finding the right tests…
Emergency services available 24 x 7
Emergency services available 24 x 7
Finding the right tests…
Hormonal
Your parathyroid glands are four pea-sized glands in your neck, separate from the thyroid despite the similar name, and they release parathyroid hormone (PTH) to keep your blood calcium in a narrow range. This test measures PTH in your blood, almost always alongside calcium, because the two only make sense read together — a PTH level that looks normal on its own can still be the wrong response to a calcium level that's high or low. Doctors order it when calcium is already abnormal, when someone has unexplained osteoporosis, or when working up kidney disease, since failing kidneys disturb calcium and PTH together. The direction your result moves points toward the glands themselves, the kidneys, or vitamin D.
This test reports the amount of parathyroid hormone in your blood, in picograms per millilitre. It's almost always ordered alongside calcium, since PTH only makes sense read next to your calcium level — the two work as a feedback pair, and a PTH result that looks normal in isolation can actually be the wrong response if calcium is high or low. Most of the time no fasting is needed, though your doctor may ask you to avoid eating beforehand if other tests are drawn at the same time. A single blood sample is enough.
Your four parathyroid glands, tucked behind your thyroid in your neck, release PTH to keep blood calcium within a narrow, steady range. When calcium drops, PTH rises to pull it back up — by releasing calcium from bone, helping your kidneys hold onto it, and activating vitamin D to improve absorption from food. When calcium is already high, PTH normally falls in response.
If PTH is high while calcium is also high, the parathyroid glands themselves are usually the problem — most often a small, benign growth on one gland, a condition called primary hyperparathyroidism. If PTH is high while calcium is normal or low, the more likely explanation is that the glands are correctly responding to a shortage, often from vitamin D deficiency, poor calcium intake, or chronic kidney disease, which disrupts calcium regulation.
A low PTH usually points to the parathyroid glands themselves under-functioning, which can follow accidental damage during thyroid surgery, an autoimmune condition, or, less commonly, taking in too much calcium. Your doctor reads your PTH and calcium results together, since either number alone can be misleading.
A normal range is generally 10 to 65 picograms per millilitre, according to MedlinePlus, though ranges vary somewhat by lab and assay. Your doctor interprets your PTH result alongside your calcium level, not on its own.
PTH and calcium work as a feedback pair, so a PTH result only makes sense once your doctor knows whether your calcium is high, low, or normal. A PTH level within the normal range can still be an abnormal response if calcium is out of range.
This combination usually points to primary hyperparathyroidism, most often caused by a small, benign growth on one of the parathyroid glands. Your doctor will likely arrange imaging of the glands to confirm this.
Yes. When vitamin D is low, less calcium is absorbed from food, so the parathyroid glands release more PTH to compensate. This pattern usually shows a normal or low calcium alongside a high PTH.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
The parathyroid glands can be accidentally damaged during thyroid surgery, or affected by an autoimmune condition, both of which reduce PTH output. Taking in too much calcium can also suppress PTH.
Usually not, though your doctor may ask you to fast if other blood tests are being done at the same time. Ask your doctor or the centre about preparation for your specific visit.