Parathyroid hormone (PTH) is the main hormone that keeps your blood calcium steady. It is made by four tiny parathyroid glands sitting behind your thyroid in the neck. On a standard blood test, a normal PTH result usually falls between 15 and 80 pg/mL — but this number only makes sense when your doctor reads it next to your calcium and vitamin D levels.
What is a parathyroid hormone (PTH) test?
The PTH test measures how much parathyroid hormone is circulating in your blood. Think of the parathyroid glands as a thermostat for calcium: when blood calcium dips, they release more PTH, which pulls calcium from your bones, tells your kidneys to hold on to calcium, and helps activate vitamin D so your gut absorbs more calcium from food. When calcium rises, PTH switches off. This tight feedback loop is why PTH is rarely read on its own.
A doctor may order a PTH test if your blood calcium is high or low, if you have kidney disease, osteoporosis or repeated bone fractures, kidney stones, or unexplained tiredness, bone aches and muscle weakness. Because calcium regulation, vitamin D status and phosphorus balance are all connected, PTH is often ordered together with a calcium blood test, vitamin D and a phosphorus test. The modern assay used by most Indian labs measures "intact PTH", which is the biologically active form.
PTH normal range
For a typical adult, intact PTH sits in the normal band shown below, measured in picograms per millilitre (pg/mL). Different laboratories may quote slightly different cut-offs depending on the assay they use, so always read your result against the reference range printed on your own report. The bands below reflect standard laboratory reference ranges used to flag how far a value sits from normal.
| PTH level (pg/mL) | How it is generally read |
|---|---|
| 15 - 80 | Normal |
| 81 - 100 | Borderline high |
| 101 - 150 | Moderately high |
| 151 - 300 | Markedly high |
| Above 300 | Very high — needs urgent review |
| 11 - 14 | Borderline low |
| 6 - 10 | Moderately low |
| Below 6 | Markedly low |
A number inside the normal band is reassuring only if your calcium is also normal. As you will see below, the same PTH value can be perfectly healthy in one person and a red flag in another, depending entirely on what calcium is doing at the same time.
Reading PTH with calcium and vitamin D
PTH is one of the few blood tests where the result is almost meaningless in isolation. The reference bands above are the same for most adults, but the interpretation shifts with age, kidney health and — above all — your calcium and vitamin D status. The table below shows how a doctor thinks about the PTH-and-calcium pair rather than PTH alone.
| PTH with calcium | What it often points to |
|---|---|
| High PTH + high calcium | Primary hyperparathyroidism — a parathyroid gland is overactive and driving calcium up. |
| High PTH + low or normal calcium | Secondary hyperparathyroidism — the glands are working overtime to compensate, commonly from vitamin D deficiency or kidney disease. |
| Low PTH + high calcium | Calcium is high from a non-parathyroid cause, so the glands have correctly switched off. |
| Low PTH + low calcium | Hypoparathyroidism — the glands are underactive, so calcium falls. |
Why the interpretation shifts by group:
- Vitamin D status: Low vitamin D is one of the most common reasons for a mildly raised PTH. When the gut cannot absorb enough calcium, the parathyroid glands release more PTH to protect blood calcium. Because vitamin D deficiency is very common in India, doctors often correct vitamin D first and then re-check PTH before concluding anything is wrong with the glands.
- Kidney health: The kidneys activate vitamin D and clear phosphorus. In chronic kidney disease, phosphorus builds up and active vitamin D falls, pushing PTH steadily higher (secondary hyperparathyroidism). A raised PTH in someone with kidney disease is read very differently from the same number in a person with healthy kidneys.
- Older adults: PTH tends to run a little higher with age, partly because vitamin D levels and kidney function decline over time. A mildly raised value in a senior is often driven by correctable vitamin D deficiency rather than gland disease.
- Pregnancy and breastfeeding: Calcium demand rises, and the body adapts its calcium-handling. PTH should be interpreted with pregnancy-appropriate expectations and alongside calcium and vitamin D, not against a fixed cut-off.
- Medications and supplements: Lithium, thiazide diuretics, calcium and vitamin D supplements, and some bone medicines can nudge PTH or calcium. Tell your doctor what you take, as this changes how the result is read.
This is the real value of a PTH test — not the single number, but the pattern it forms with calcium, vitamin D and phosphorus.
What high PTH means
A raised PTH is called hyperparathyroidism, and it comes in two main forms. In primary hyperparathyroidism, one or more parathyroid glands become overactive (often from a small benign growth) and pump out PTH even though calcium is already high — so you typically see high PTH together with high calcium. In secondary hyperparathyroidism, the glands are responding appropriately to a problem elsewhere — usually vitamin D deficiency or chronic kidney disease — so PTH is high while calcium is low or normal.
Many people with mildly high PTH feel nothing at all. When symptoms do appear, they can include tiredness, low mood, bone and joint aches, muscle weakness, excessive thirst, frequent urination, constipation, and kidney stones. Over years, sustained high PTH can thin the bones and raise the risk of fractures. On the bands above, values above 80 pg/mL are flagged as borderline or high, and levels above 300 pg/mL warrant urgent medical review. Your doctor will usually repeat the test and add calcium, vitamin D, phosphorus and kidney tests before deciding what — if anything — needs treating.
What low PTH means
A low PTH (a value in the lower bands above, particularly below 15 pg/mL) means the parathyroid glands are producing little hormone. Sometimes this is exactly right — if blood calcium is high from another cause, healthy glands correctly switch PTH off. But if calcium is also low, it points to hypoparathyroidism, where the glands are underactive. The most common reason worldwide is accidental damage to or removal of the parathyroid glands during thyroid or neck surgery; less often it follows an autoimmune process or, rarely, low magnesium.
Low calcium from underactive glands can cause tingling around the mouth and in the fingers, muscle cramps or spasms, and in severe cases more serious symptoms. Because low PTH is far less common than high PTH, it is usually picked up only after a calcium abnormality prompts testing. As always, the PTH number is interpreted alongside calcium.
How to manage and improve your PTH
PTH is a marker your doctor tracks — you do not "lower PTH" directly the way you might manage blood sugar. Instead, you address the underlying driver, and the most common correctable driver is vitamin D. Practical, evidence-aligned steps include:
- Correct vitamin D deficiency: Sensible sunlight exposure and, when a doctor advises it, vitamin D supplementation often bring a mildly raised (secondary) PTH back down. This is frequently the single most useful step in India, where deficiency is widespread even in sunny cities.
- Get enough dietary calcium: Indian sources include milk, curd, paneer, ragi (finger millet), til (sesame seeds), green leafy vegetables and fortified foods. Adequate calcium reduces the stimulus for the glands to over-secrete PTH.
- Look after your kidneys: Because kidney disease is a major driver of high PTH, controlling blood pressure and diabetes and following your doctor's advice on phosphorus intake matters. Phosphorus balance and PTH move together, which is why a phosphorus test is often ordered at the same time.
- Stay hydrated and stay active: Good fluid intake supports kidney function and calcium handling, and weight-bearing activity supports bone strength.
- Review your medicines: If you take lithium, thiazides or calcium/vitamin D supplements, ask your doctor whether they could be affecting your result.
When to see a doctor: Book a review if your PTH is outside the normal band, if your calcium is high or low, or if you have kidney stones, thinning bones, or persistent tiredness, bone pain or muscle weakness. High PTH with high calcium, or any very high value, should be assessed promptly. If you are monitoring bone and hormone markers over time, keeping your reports together with ExaHealth makes it easier for you and your doctor to see the PTH-calcium-vitamin D pattern change from one test to the next. You can explore more markers in our lab tests library.
Guidelines and references
The bands in this article reflect standard laboratory reference ranges for intact PTH; your own lab's printed range takes precedence, as cut-offs vary by assay. PTH is always interpreted together with calcium and vitamin D.
- Standard laboratory reference ranges for intact parathyroid hormone (pg/mL), as reported by clinical laboratories.
- The Endocrine Society — general endocrine and calcium-metabolism education.
Frequently asked questions
What is the normal range for PTH?
For most adults, intact PTH is normal between about 15 and 80 pg/mL. Because assays differ, always compare your result with the reference range printed on your own lab report.
Why is PTH tested along with calcium?
PTH controls blood calcium, so the two must be read together. The same PTH value can be normal or abnormal depending on whether calcium is high, low or normal at the same time.
What does high PTH mean?
High PTH is called hyperparathyroidism. With high calcium it usually means an overactive parathyroid gland; with low or normal calcium it often means the glands are compensating for vitamin D deficiency or kidney disease.
Can vitamin D deficiency raise PTH?
Yes. Low vitamin D reduces calcium absorption, so the parathyroid glands release more PTH to protect blood calcium. This is one of the most common reasons for a mildly raised PTH, and it is very common in India.
What does low PTH mean?
Low PTH means the glands are making little hormone. If calcium is also low, this points to hypoparathyroidism, most often after thyroid or neck surgery. If calcium is high, low PTH can simply be the glands correctly switching off.
How can I bring a high PTH down?
You treat the cause rather than the number. Correcting vitamin D deficiency, getting enough dietary calcium and looking after kidney health often lowers a mildly raised (secondary) PTH. Discuss your specific result with your doctor.