How to Convert PTH pmol/L to pg/mL
Parathyroid hormone is reported in pg/mL (or ng/L) in the US and in pmol/L across much of the world. The conversion factor is 9.43, from PTH's molecular weight of about 9,424.
PTH pg/mL = PTH pmol/L × 9.43 PTH pmol/L = PTH pg/mL × 0.1061 pg/mL and ng/L are identical for PTH, so 45 pg/mL is the same as 45 ng/L — no calculation needed between those two.
PTH pmol/L to pg/mL Chart
| pmol/L | pg/mL (ng/L) | Context |
|---|---|---|
| 1.0 pmol/L | 9.4 pg/mL | Low |
| 1.6 pmol/L | 15.1 pg/mL | Lower normal |
| 3.0 pmol/L | 28.3 pg/mL | Mid-normal |
| 6.9 pmol/L | 65.1 pg/mL | Upper normal |
| 10 pmol/L | 94.3 pg/mL | High |
| 20 pmol/L | 188.6 pg/mL | Markedly high |
pg/mL to pmol/L Reverse Chart
| pg/mL (ng/L) | pmol/L |
|---|---|
| 10 pg/mL | 1.06 pmol/L |
| 15 pg/mL | 1.59 pmol/L |
| 65 pg/mL | 6.90 pmol/L |
| 100 pg/mL | 10.61 pmol/L |
PTH Reference Range
For intact PTH, a common reference range is 15–65 pg/mL (1.6–6.9 pmol/L). Ranges vary by assay and are strongly affected by vitamin D status, so compare against your own lab's interval. Newer bio-intact (whole) PTH assays use a slightly lower range, so results are only comparable within the same assay.
Reading PTH With Calcium: The Interpretation Grid
This is the part a bare converter never shows — and it is what actually matters. PTH raises blood calcium, so PTH is only meaningful next to the calcium level. The same PTH number means completely different things depending on calcium:
| Calcium | PTH | Typical picture |
|---|---|---|
| High | High or inappropriately normal | Primary hyperparathyroidism |
| High | Low (suppressed) | Non-PTH hypercalcemia (e.g. malignancy, high vitamin D) |
| Low | High | Secondary hyperparathyroidism (vitamin D deficiency, kidney disease) |
| Low | Low or normal | Hypoparathyroidism |
| Normal | High | Normocalcemic primary or early secondary hyperparathyroidism |
Convert calcium units on the calcium conversion calculator — and when albumin is low, use the albumin-corrected calcium before reading it against PTH, since a low albumin makes total calcium look falsely low. Remember too that low vitamin D drives PTH up (secondary hyperparathyroidism), so the two are usually checked together.
PTH in Chronic Kidney Disease (Secondary Hyperparathyroidism)
One of the most common reasons PTH is ordered is chronic kidney disease (CKD), where it typically rises — secondary hyperparathyroidism. The important point is that the target is different here. Rather than the normal 15–65 pg/mL, guidelines (KDIGO) suggest keeping PTH roughly 2–9 times the upper limit of normal for patients on dialysis, because some elevation is expected and helps protect bone. So a PTH that looks "high" against the standard range can be appropriate in dialysis — it must be read in the CKD context with a nephrology team, not against the general reference range.
Worked Example
Suppose a report shows 12 pmol/L PTH and you want pg/mL:
12 × 9.43 = 113 pg/mL (= 113 ng/L) 113 pg/mL is above the normal range. Whether that points to primary or secondary hyperparathyroidism depends on the calcium — hence the grid above.
Frequently Asked Questions
How do you convert PTH pmol/L to pg/mL?
Multiply pmol/L by 9.43. For example, 5 pmol/L is about 47 pg/mL.
Is pg/mL the same as ng/L?
Yes, they are identical for PTH (1:1).
What is a normal PTH?
Intact PTH is roughly 15–65 pg/mL (1.6–6.9 pmol/L), varying by assay.
Why read PTH with calcium?
The same PTH means different things at high vs low calcium — see the grid above.
References
- UnitsLab — Parathyroid hormone (PTH) unit conversion (pmol/L ↔ pg/mL).
- PTH factor 9.43 (MW ≈ 9,424); intact PTH reference range 15–65 pg/mL (1.6–6.9 pmol/L) from standard clinical laboratory references.
Conclusion
Converting PTH between pmol/L and pg/mL is a ×9.43 (and pg/mL = ng/L). But the number only comes alive next to calcium: the interpretation grid above is what turns a converted PTH into a meaningful result. Interpret it with calcium, vitamin D and your clinician.