Blood test
Parathyroid Hormone Test
A parathyroid hormone (PTH) test measures a hormone that controls calcium levels, used to investigate high or low blood calcium.
Quick answer
Parathyroid Hormone Test: what it is and what the results mean
PTH is made by the parathyroid glands in the neck and regulates calcium in the blood and bones. A blood test measures its level, usually alongside a calcium test, to understand calcium disorders.
- Why it is done: It is used to find the cause of high or low blood calcium, to investigate parathyroid gland problems (such as an overactive gland or a tumour), bone disease, kidney disease and vitamin D problems.
- Understanding results: PTH is interpreted together with calcium: high PTH with high calcium suggests an overactive parathyroid gland, while high PTH with low calcium suggests the body is compensating (for example in vitamin D deficiency or kidney disease).
What it is
PTH is made by the parathyroid glands in the neck and regulates calcium in the blood and bones. A blood test measures its level, usually alongside a calcium test, to understand calcium disorders.
Why it is done
It is used to find the cause of high or low blood calcium, to investigate parathyroid gland problems (such as an overactive gland or a tumour), bone disease, kidney disease and vitamin D problems.
What to expect
It is an ordinary blood test from a vein in the arm, usually taken together with a calcium sample. No special preparation is normally needed, though timing may matter.
Understanding the results
PTH is interpreted together with calcium: high PTH with high calcium suggests an overactive parathyroid gland, while high PTH with low calcium suggests the body is compensating (for example in vitamin D deficiency or kidney disease).
Good to know
Risks and limitations
It is a safe blood test. It must always be interpreted alongside calcium and often vitamin D and kidney function, as PTH alone does not give the full picture.
Education and reference only. This explains the test in general terms and is not medical advice. Always follow the specific instructions from the team arranging your test, and discuss your results with your clinician.
Answers
Parathyroid Hormone Test: frequently asked questions
Why is calcium measured at the same time as PTH?
PTH and calcium work together, so interpreting them as a pair reveals the cause of a calcium problem. The same PTH value can mean very different things depending on the calcium level.
What does a high PTH mean?
It depends on the calcium level. High PTH with high calcium often points to an overactive parathyroid gland, while high PTH with low or normal calcium may reflect the body compensating for low vitamin D or kidney disease.
Related tests
Other blood test investigations
Sources
Where this is drawn from
- NHS — Tests and treatments
- NICE — diagnostic guidance
- Association for Laboratory Medicine / relevant professional body
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