Parathyroid hormone (PTH) test: normal range
In the source: 10–65 pg/ml, converted to pmol/l using the standard factor ×0.106 (molecular mass of intact PTH ~9,400 Da)
- Updated
- 2026-09-10
- Every number with its source
What parathyroid hormone is and why it is assessed with calcium
Parathyroid hormone (PTH) is a hormone produced by four small parathyroid glands that lie next to the thyroid in the neck. Its main job is to keep the amount of calcium in the blood stable: when calcium falls, the PTH level rises and promotes the release of calcium from the bones, its absorption in the gut (together with vitamin D) and its retention in the kidneys. When there is enough calcium in the blood, or too much of it, PTH production decreases. That is why a PTH test is almost always assessed together with the amount of calcium in the blood — and often with vitamin D and phosphorus too: only by seeing both values together is it possible to understand whether the parathyroid glands are working properly. PTH disorders are divided into hyperparathyroidism (the glands are too active) and hypoparathyroidism (they are not active enough), and the cause may be in the glands themselves or elsewhere in the body, for example in the kidneys or in a lack of vitamin D.
Reference range
| Group | Range, pmol/l | Source |
|---|---|---|
| Adults In the source: 10–65 pg/ml, converted to pmol/l using the standard factor ×0.106 (molecular mass of intact PTH ~9,400 Da) | 1.1–6.9 | MedlinePlus Reviewed 2025-10-19 |
According to MedlinePlus, the range for adults is 10–65 pg/ml, or about 1.1–6.9 pmol/l. The exact interval depends on the laboratory's method — the range that applies to your result is the one printed on your own lab report. A PTH result is almost always assessed together with the amount of calcium in the blood, and often with vitamin D and phosphorus as well; only both values together show whether the parathyroid glands are working properly.
When a PTH test is done
- When a general or biochemical blood test has found a raised or reduced amount of calcium in the blood
- When a reduced amount of phosphorus in the blood has been found
- When a parathyroid disorder is suspected — hyperparathyroidism or hypoparathyroidism
- In chronic kidney disease — to assess how impaired kidney function affects calcium and PTH metabolism
- In severe, unexplained osteoporosis
- To monitor treatment for parathyroid or calcium metabolism disorders
How to prepare
- Most often no special preparation is needed, but your doctor may ask you not to eat or drink for a certain time before the test
- Ask your doctor whether you need to stop taking calcium or vitamin D supplements for a while before the test
A raised PTH
A raised PTH most often indicates a parathyroid adenoma (a benign growth) causing primary hyperparathyroidism. Other causes are chronic kidney disease and a lack of calcium or vitamin D, because of which the glands produce more PTH to compensate (secondary hyperparathyroidism). Assessing the amount of calcium in the blood at the same time helps to tell the cause apart.
- A parathyroid adenoma (a benign growth) — the most common cause
- Chronic kidney disease
- A lack of calcium
- Vitamin D deficiency or another disorder of vitamin D metabolism
- Not enough calcium in the diet, or its poor absorption in the digestive tract
- Rarely — inherited syndromes (for example multiple endocrine neoplasia) or parathyroid cancer
What to discuss with a doctor
- The amount of calcium in the blood — assessed together with PTH, so that it is clear whether the hyperparathyroidism is primary or secondary
- Vitamin D and phosphorus tests
- Kidney function markers (creatinine, GFR)
- An assessment of bone density, if the disorder has been going on for a long time
A low PTH
A low PTH (hypoparathyroidism) most often indicates damage to the parathyroid glands — usually their accidental removal or damage during thyroid surgery, or their autoimmune destruction. Other causes are too much calcium or vitamin D, a low magnesium level and radiation therapy.
- Accidental damage to or removal of the parathyroid glands during thyroid surgery
- Autoimmune damage to the parathyroid glands
- Excessive use of calcium or vitamin D supplements
- A reduced amount of magnesium in the blood
- Cancer that has spread to the bones
- Radiation therapy to the neck area
- Serious illnesses
What to discuss with a doctor
- The amount of calcium and magnesium in the blood
- The vitamin D level
- The medical history — whether there has been thyroid surgery or radiation therapy to the neck
- Symptoms related to low calcium (muscle spasms, numbness), which are worth discussing with a doctor
Related pages
Related pages on this site: calcium, vitamin D, phosphorus, magnesium, creatinine, GFR, osteocalcin and how to read a blood test result. Pages in the /rodikliai/ section are in Lithuanian.
Full site in Lithuanian: proactiva.app
Frequently asked questions
›What is the normal parathyroid hormone (PTH) range?
According to MedlinePlus, the range for adults is 10–65 pg/ml, or about 1.1–6.9 pmol/l. The exact interval depends on the laboratory's method — you will find the range on your own lab report.
›Why is a PTH test always assessed together with calcium?
The function of PTH is directly linked to the amount of calcium in the blood — the hormone rises when calcium is lacking and falls when there is enough of it. Assessing PTH and calcium together makes it possible to tell whether the parathyroid glands are disturbed in a primary way, or whether this is the body's response to another cause, for example a lack of vitamin D.
›What is the most common cause of a raised PTH?
According to MedlinePlus, the most common cause is a parathyroid adenoma — a benign growth in one of the parathyroid glands, causing primary hyperparathyroidism. Other causes are chronic kidney disease and a lack of calcium or vitamin D.
›Why can PTH be low?
The most common cause is damage to the parathyroid glands or their accidental removal during thyroid surgery. It can also be due to autoimmune damage to the glands, excessive use of calcium or vitamin D, or a low amount of magnesium in the blood.
›Do I need to fast before a PTH test?
Most often no special preparation is needed, but your doctor may ask you not to eat or drink for a certain time before the test. It is worth asking your doctor whether you need to stop taking calcium or vitamin D supplements for a while.
›When does a doctor order a PTH test?
Most often when a blood test has found a deviating amount of calcium or phosphorus, when a parathyroid disorder is suspected, in chronic kidney disease, or in severe unexplained osteoporosis.
Sources
Related markers
This site is not an emergency service. If severe chest or head pain, breathlessness, confusion, difficulty speaking, heavy bleeding or another acute problem has come on suddenly — do not wait for tests, call 112.
This information is not a diagnosis and does not replace a consultation with a doctor. Reference ranges depend on the laboratory, your age and sex — always compare your result with the range printed on your own report.