Parathyroid hormone (PTH) blood test in Chiswick

What the test measures

Parathyroid hormone is made by four small glands in the neck, sitting behind the thyroid. Its job is to keep the amount of calcium in the blood within a tight range. When calcium falls, PTH rises: it releases calcium from bone, helps the kidneys hold on to calcium and switches on the active form of vitamin D, which increases calcium absorption from food.

Because PTH and calcium work as a pair, the result is most meaningful when read with a calcium level taken at the same time, and often with vitamin D, phosphate and kidney function. Together they help show whether the parathyroid glands are responding as expected.

Your price includes the sample taken at our Chiswick clinic, analysis at the Randox accredited laboratory, a practitioner review of your result and a GP feedback report on request. No GP referral is needed.

Who it is for

• A previous blood test showed raised or low calcium and you want to understand why.
• You have low bone density, osteoporosis or a fracture after a minor fall.
• You have low vitamin D and want to see whether it is affecting calcium balance.
• You have kidney stones, or a condition affecting your kidneys.
• Your GP or practitioner has asked for PTH as part of a bone health review.

Understanding your result

PTH is always read in relation to calcium. A raised PTH with a raised calcium can suggest one of the parathyroid glands is overactive, known as primary hyperparathyroidism, which is often found by chance on routine tests. A raised PTH with normal or low calcium is commonly a response to low vitamin D, low calcium intake or reduced kidney function. A low PTH with a high calcium usually means the glands are correctly switching off and another cause for the calcium needs looking at, while a low PTH with low calcium can point to underactive glands, for example after neck surgery.

Your report shows the laboratory reference range. A result outside it is a prompt for discussion with your practitioner, not a diagnosis.

Preparing for your test

Fasting is not usually required, but PTH varies through the day, so a morning appointment helps when you are comparing results over time. Stop biotin supplements, including hair, skin and nail products that contain it, for at least two days beforehand, as biotin can interfere with PTH assays. Tell us if you take calcium, vitamin D, lithium or diuretics, and bring any previous calcium results.

PTH is included in Advanced GP3, which also covers calcium, vitamin D and kidney function, and in Omnia Signature. To check vitamin D on its own, see Vitamin D, or browse every blood test and price in Chiswick.

Questions

How much is a PTH blood test in Chiswick?

A parathyroid hormone test costs £119. This includes your sample at our clinic, laboratory analysis, a practitioner review of your result and a GP feedback report on request.

Why should calcium be checked at the same time?

PTH only makes sense next to calcium. A PTH level that looks normal can still be inappropriate if calcium is raised, so the two are read together.

Can low vitamin D raise my PTH?

Yes. When vitamin D is low, less calcium is absorbed from food, and the parathyroid glands make more PTH to compensate. This often settles once vitamin D is corrected under advice.

Can this test diagnose osteoporosis?

No. Osteoporosis is diagnosed with a bone density scan. PTH helps look for causes of bone loss that might be treatable.