What is PTH (parathyroid hormone)?
Behind your thyroid lie four glands the size of a grain of rice, the parathyroid glands. They do one thing: measure the calcium in your blood and adjust it. If it falls, they release PTH, parathyroid hormone, and that works in three places at once. It pulls calcium out of your bones, makes your kidneys excrete less calcium and more phosphate, and sets in motion the conversion of vitamin D in the kidneys, so your gut absorbs more calcium. If calcium rises, the glands switch off again. PTH is therefore not a value that says something about calcium itself, but about the effort your body puts in to keep it in place. That is also why it can never be read on its own: the same PTH means something different beside a low calcium than beside a high one. Your report shows PTH in pmol/L. Normal is about 1.6 to 4.0 pmol/L where the labs overlap, but the range differs per lab more than for most values, because the assays differ and the hormone breaks down fast; the range on your own report is the most useful here. It is drawn in a chilled tube and processed quickly.
Why is PTH (parathyroid hormone) relevant?
The most common reason PTH sits high is a vitamin D deficiency, and that is exactly why it is interesting for anyone who wants to stay healthy. Without enough vitamin D your gut absorbs too little calcium, the calcium in your blood dips a fraction, and the parathyroid glands pull harder: PTH rises and takes the difference from your bone. You do not notice it, but it costs bone for years. A slightly raised PTH with a normal calcium is therefore often the first sign that your vitamin D is too low for your bones, even before the vitamin D number itself raises the alarm. More sun, oily fish and where needed a supplement let PTH fall again. Little calcium in the diet, especially in anyone who does not use dairy, does the same. The second reason is a kidney function that is declining. The kidney converts vitamin D into its active form and excretes phosphate; if it does that less, PTH rises to compensate, and that is one of the ways chronic kidney disease damages bone. The third reason is rarer and different: a parathyroid gland that makes too much by itself, usually from a benign growth. Then PTH sits high while calcium is high too, because the gland no longer listens to the thermostat. That gives osteoporosis, kidney stones, tiredness and low mood, and it is very treatable with a small operation. The distinction from the ordinary, responding rise sits in the calcium beside it, and that is the whole art of reading PTH.
PTH (parathyroid hormone) reference ranges
What counts beside the number:
- Calcium from the same draw: high PTH with low or normal calcium is correcting, high PTH with high calcium is the gland itself
- Vitamin D, the most common reason for a high PTH
- Creatinine and eGFR, because the kidney activates vitamin D and excretes phosphate
- Phosphate and magnesium, the rest of the regulatory system
- How much calcium you eat, and whether you use dairy
- Your own lab's range, because that differs strongly here
The band above is where the labs overlap, and for PTH that is a narrow part of what each lab uses on its own: the assays differ and the hormone breaks down fast. So compare your value with the range on your own report and follow it at the same lab. There is no national normal value, and in chronic kidney disease PTH is no longer measured as standard because the best value there is not known. Always read PTH beside calcium.
What Dutch labs actually use
The four labs diverge further on PTH than on the other salts on this site. Unilabs sets the band at 1.3 to 8.3 pmol/L, Star-shl and Certe both at 1.6 to 6.9, and Clinical Diagnostics at 0.7 to 4.0. That last upper limit sits below the midpoint of what Unilabs still calls normal. A value of 4.0 pmol/L is exactly the ceiling at Clinical Diagnostics and comfortably inside the normal range at Unilabs. Part of that difference is not in the limits but in the test itself. Unilabs measures PTH in EDTA plasma drawn into an ice-cold tube, Star-shl measures it in serum, and the two labs use different immunoassays. These are not two readings of the same number with a different margin around them.
1.6 – 4.0pmol/L
Between 0.7 and 1.6 and between 4.0 and 8.3 it depends on the lab, because each sets its limits on its own method and population. Above 8.3 every lab calls it abnormal.
every lab calls 1.6 – 4.0 pmol/L normal. Between 0.7 and 1.6 and between 4.0 and 8.3 it depends on the lab.
Every age, per lab
| Laboratory | Group | Reference range |
|---|---|---|
| Unilabs(Saltro, Medlon, SHO, Atalmedial)2026 | All ages | 1.3–8.3 pmol/L |
| Star-shl2026 | All ages | 1.6–6.9 pmol/L |
| Certe2026 | From 18 yrs | 1.6–6.9 pmol/L |
| Clinical Diagnostics2026 | All ages | 0.7–4.0 pmol/L |
Each band as the lab publishes it, retrieved in 2026, unless marked otherwise.
PTH (parathyroid hormone) high or low: what it means
A high PTH is, in order of how often it occurs: a vitamin D deficiency, reduced kidney function, too little calcium in the diet or poor absorption of it, a parathyroid gland making too much by itself, and rarely lithium or an inherited cause. The key is the calcium beside it. High PTH with a low or normal calcium is a gland correcting, and then you look for the cause in vitamin D, the kidneys and the diet. High PTH with a high calcium is a gland that is itself the source, and then investigation of the parathyroid glands belongs to it. A low PTH means the glands are switching off or no longer can: a high calcium coming from elsewhere, from too much vitamin D or calcium as a supplement, or rarely from a malignant condition; damage to the glands after surgery in the neck; or a severe magnesium deficiency, because without magnesium they cannot release PTH. Low PTH with a high calcium is therefore a reason to look further, low PTH with a normal calcium usually not. What you do about it: with a high PTH and a normal calcium, vitamin D is almost always the lever, with daylight, oily fish and a supplement in winter, and enough calcium from dairy, green vegetables, nuts and legumes. Count on a few months before PTH falls with it. With reduced kidney function, phosphate and vitamin D belong to the treatment. A gland that makes too much by itself is not solved with lifestyle, and does not always need treating either. Always read PTH beside calcium, and beyond that beside vitamin D, phosphate, magnesium and your kidney function. And when comparing over time, keep to one and the same lab, because the ranges differ strongly here.
What lowers it
The glands switching off, or no longer able to.
| Cause | How often |
|---|---|
| A raised calcium coming from elsewhereToo much vitamin D or calcium as a supplement, and rarely a malignant condition; the parathyroid glands then rightly switch off | Sometimes |
| Damage to the parathyroid glands after surgery in the neckThe glands lie just behind the thyroid and can be damaged in an operation; calcium then falls with it | Sometimes |
| A magnesium deficiencyWithout magnesium the glands cannot release PTH; with plenty of alcohol, diuretics or antacids that occurs | Rare |
What raises it
Almost always a gland responding to something; the question is to what.
| Cause | How often |
|---|---|
| A vitamin D deficiencyWithout enough vitamin D the gut absorbs too little calcium and the parathyroid glands pull harder; the most common reason, and reversible with daylight, oily fish and a supplement | Often |
| Reduced kidney functionThe kidney converts vitamin D into its active form and excretes phosphate; if it does that less, PTH rises to compensate | Often |
| Too little calcium in the diet or poor absorptionIn anyone who does not use dairy, with coeliac disease or after stomach surgery; the glands make up the shortfall from bone | Sometimes |
| A parathyroid gland that releases too much by itselfUsually a benign growth; PTH then sits high beside a high calcium, and that is the distinction from all the causes above | Sometimes |
| Lithium useLithium shifts the thermostat of the parathyroid glands, so they release more PTH at the same calcium | Rare |
How does a PTH (parathyroid hormone) blood test work?
- Referral
- Not needed, though the draw is not possible at every location because the tube has to be chilled and processed quickly.
- Fasting
- Not needed, but have blood drawn in the morning and always at the same time, because PTH has a daily rhythm.
- The draw
- One tube of blood from a vein in your arm, chilled and processed quickly, because the hormone breaks down fast. Calcium comes from the same draw.
- The result
- A single number in pmol/L, with a range that differs strongly per lab because of different assays; compare only with the range on your own report.
- Where to draw
- You can draw at 250+ locations near you, no referral needed. See the locations
Frequently asked questions
What is PTH?
Parathyroid hormone, the hormone of the four parathyroid glands behind your thyroid. They measure the calcium in your blood and release more PTH when it falls; the hormone then pulls calcium out of your bones, makes your kidneys excrete less calcium and sets vitamin D to absorbing more calcium from the gut. PTH therefore does not say how much calcium you have, but how hard your body works to keep it in place.
What is a normal PTH level?
About 1.6 to 4.0 pmol/L where the labs overlap, but the range differs per lab more than for most values, because the assays differ. The range on your own report is the most useful here, and a value can only be compared over time at the same lab.
What does a raised PTH mean?
Almost always that the parathyroid glands are responding to something. Beside a low or normal calcium that is usually a vitamin D deficiency, a kidney function working less, or too little calcium in the diet; the gland is then correcting and the cause is reversible. Beside a high calcium the gland itself is the source, usually from a benign growth, and investigation of the parathyroid glands belongs to it. The calcium beside it therefore makes the difference.
What does a low PTH mean?
That the parathyroid glands are switching off or no longer can. Beside a high calcium the calcium comes from elsewhere, from too much vitamin D or calcium as a supplement, or rarely from a malignant condition, and looking further is needed. Beside a low calcium it points at damage after surgery in the neck or a severe magnesium deficiency. Beside a normal calcium a low PTH usually means nothing.
What does vitamin D have to do with PTH?
Everything. Without enough vitamin D your gut absorbs too little calcium, calcium dips a fraction and the parathyroid glands pull harder: PTH rises and takes the difference from your bone. A slightly raised PTH with a normal calcium is therefore often the first sign that your vitamin D is too low for your bones. Daylight, oily fish and a supplement in winter let PTH fall within a few months.
Can I lower my PTH myself?
If the cause is vitamin D or calcium, yes: enough daylight, oily fish, a vitamin D supplement in winter, and calcium from dairy, green vegetables, nuts and legumes. Count on a few months. With reduced kidney function, phosphate and vitamin D belong to the treatment. A parathyroid gland that makes too much by itself you do not lower with lifestyle; that is followed or fixed with a small operation.
Why do the labs differ so strongly on PTH?
Because they work with different assays and the hormone breaks down fast, so the way of drawing and transporting also carries through into the outcome. That sits in the measurement, not in your blood. So compare your value only with the range on your own report, and have a repeat done at the same lab.
Do I need to fast for a PTH test?
No, but have blood drawn in the morning and always at the same time, because PTH has a daily rhythm. The tube is chilled and processed quickly, and calcium should come from the same draw, because without calcium PTH cannot be read.
Which tests include PTH (parathyroid hormone)?
PTH (parathyroid hormone) is part of Advanced, the broader panel. It is not orderable yet.
Related biomarkers
Sources
- 1.Unilabs, test catalogue (Dutch): parathyroid hormone. 2026. bepalingenklapper.nl
- 2.Star-shl, test catalogue (Dutch): parathyroid hormone intact (PTH). 2026. star-shl.nl
- 3.Certe, test catalogue (Dutch): PTH intact. 2026. bepalingenwijzer.certe.nl
- 4.Clinical Diagnostics, lab guide (Dutch): parathyroid hormone (PTH). 2026. clinicaldiagnostics.nl
- 5.NHG guideline on chronic kidney disease (M109), Dutch College of General Practitioners. 2026. richtlijnen.nhg.org
- 6.LESA Laboratory diagnostics (Dutch primary-care laboratory agreement). 2026. richtlijnen.nhg.org
- 7.Dutch chronic kidney disease guideline: secondary hyperparathyroidism. 2026. richtlijnendatabase.nl
- 8.Hypomagnesaemia, Drug and Therapeutics Bulletin 51(3). 2013. pubmed.ncbi.nlm.nih.gov
Educational information only, not medical advice. Consult a healthcare professional for clinical decisions.
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PTH (parathyroid hormone) is part of Advanced, the broader panel. It is not orderable yet.
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