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Parathyroid hormone (PTH) is a hormone that controls the amount of calcium in your blood. A value that is too high can point to parathyroid glands that make too much PTH, or to a shortage of something like vitamin D. A value that is too low can point to parathyroid glands that cannot make enough PTH.[1]
On this page, you can read what parathyroid hormone is, what the guidelines say about a value that is too low or too high, what affects your value and which other values are best to look at alongside it.
Also known as: parathyroid hormone, parathormone, intact PTH. At the lab: PTH.
Parathyroid hormone, PTH for short, is made by your parathyroid glands. These are four glands the size of a pea, in your neck. Hormones are chemical messengers in your blood. They control certain cells or organs.[1]
PTH controls the calcium in your blood. Most of your calcium is in your bones and teeth. Having the right amount of calcium in your blood matters for your nerves, your muscles and your heart.[1]
If your calcium is too low, your parathyroid glands release PTH. Your bones then release calcium into your blood, your gut absorbs more calcium from your food and your kidneys hold on to calcium instead of losing it through your urine. Once your calcium is back to normal, the glands stop and your PTH falls. PTH also helps regulate the amount of phosphate in your blood.[1]
A PTH test mostly helps work out whether the parathyroid glands are the cause of an abnormal calcium level. Doctors also use the test to explain a low phosphate level, to monitor people with a long-term kidney condition and to look for the cause of severely weakened bones that break easily.[1]
A PTH test can be useful if an earlier calcium measurement was not normal, or if you have symptoms that fit too much calcium. Think of constipation, nausea, stomach pain, a lot of thirst, needing to pee more often, tiredness or confusion.[1]
Symptoms that fit too little calcium can also be a reason. Think of muscle cramps, tingling in your lips, tongue, fingers and feet, or an irregular heartbeat.[1]
In 2022, an international group of more than 50 experts published new guidelines on investigating overactive parathyroid glands. Compared with the 2014 guidelines, it is mainly the recommendations about the kidneys that were revised.[2]
Labplusarts, the lab BioProfile works with, uses a reference range of 1.6 to 6.9 pmol/l for parathyroid hormone. The lab calls a level between those limits normal.[3]
| Your PTH level | What it can mean | Who it is for |
|---|---|---|
| Higher than normal[1] | Can point to parathyroid glands that themselves make too much PTH | If your calcium is also high |
| Higher than normal[1] | Can point to parathyroid glands that work well and make extra PTH, while the cause lies outside the glands | If your calcium is low |
| Lower than normal[1] | Can point to parathyroid glands that cannot make enough PTH | If your calcium is also low |
| Doesn't match your calcium[1] | Your doctor will usually request further blood tests | When PTH doesn't fit your calcium and other results |
Source: MedlinePlus, U.S. National Library of Medicine. Applies to PTH read alongside your blood calcium, not as a value on its own.[1]
A low PTH together with a low calcium can point to parathyroid glands that cannot make enough PTH. This is less common than a PTH that is too high. Possible causes include damage to the glands after surgery on your neck or after radiation therapy, certain autoimmune conditions, certain inherited conditions, too much vitamin D or calcium from supplements or from antacids containing calcium, and serious illness.[1]
A high PTH together with a high calcium can point to a problem in the parathyroid glands themselves, which makes them produce too much PTH. A high PTH together with a low calcium can point to glands that work well and make extra PTH to bring your calcium up. The cause then often lies outside them, such as a shortage of vitamin D, phosphate or magnesium, too little calcium, difficulty absorbing calcium from your food, or kidneys that are not doing their job properly. Your doctor will then usually request further tests.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
Your PTH moves with your calcium. If your calcium falls, your parathyroid glands make more PTH. Once your calcium is back to normal, your PTH falls.[1]
A shortage of vitamin D, phosphate or magnesium, too little calcium from your food, a digestive condition that makes it harder to absorb calcium, or kidneys that lose too much calcium through your urine can go together with a higher PTH.[1]
Too much vitamin D or calcium from supplements, or from antacids that contain calcium, can go together with a low PTH.[1]
You usually don't need to prepare for a PTH test. Sometimes a doctor will ask you to come in fasting or to have the test done at a certain time of day.[1]
Parathyroid hormone is included in BioProfile 150.[4]
The BioProfile editorial team wrote this page on 10 October 2026 from the sources below, which we read on 10 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert has yet to check this page; after that check, the expert's name and the date of the check will appear at the top. This page offers explanation, not a diagnosis. Discuss a value outside the range with your GP.
