Calcium/PTH Calculator

Calcium disorder workup from calcium, PTH, and vitamin D.

Medical Disclaimer

This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.

Inputs

Total Calcium (mg/dL)

Albumin (g/dL)

PTH (pg/mL)

25-OH Vitamin D (ng/mL)

Tab to move between fields

Results

Corrected Calcium (mg/dL)

9.5

Est. Ionized Ca (mg/dL)4.75

Calcium Status (0–2)1

PTH Status (0–2)1

Vitamin D Status (0–3)2

Diagnosis Pattern (0–4)0

How to Use This Calculator

Enter Total Calcium (mg/dL) and Albumin (g/dL) from the lab report.
Input PTH (pg/mL) and 25-OH Vitamin D (ng/mL).
Review Corrected Calcium (mg/dL) — adjusted for hypoalbuminemia.
Check Calcium Status, PTH Status, and Vitamin D Status for each axis.
Use the Diagnosis Pattern to guide workup: primary hyperparathyroidism, vitamin D deficiency, hypoparathyroidism, etc.

How the result changes with Total Calcium (mg/dL)

Total Calcium (mg/dL)	Corrected Calcium (mg/dL)
2.9	2.9
7.65	7.65
13	13
18	18

What each input means

Total Calcium (mg/dL): Serum total calcium. Normal range 8.5–10.5 mg/dL.
Albumin (g/dL): Serum albumin. Used to correct calcium for protein binding.
PTH (pg/mL): Intact parathyroid hormone level. Normal range 15–65 pg/mL.
25-OH Vitamin D (ng/mL): 25-hydroxyvitamin D level. Deficient <20, insufficient 20–29, sufficient 30–100.

What each result means

Corrected Calcium (mg/dL): Calcium corrected for albumin (Payne formula): Ca + 0.8 × (4.0 − Albumin).
Est. Ionized Ca (mg/dL): Rough estimate of ionized calcium (≈ total / 2). Lab measurement is more accurate.
Calcium Status (0–2): 0 = Low (<8.5), 1 = Normal (8.5–10.5), 2 = High (>10.5).
PTH Status (0–2): 0 = Low (<15), 1 = Normal (15–65), 2 = High (>65).
Vitamin D Status (0–3): 0 = Deficient (<20), 1 = Insufficient (20–29), 2 = Sufficient (30–100), 3 = Excess (>100).
Diagnosis Pattern (0–4): 0 = Normal, 1 = Primary hyperparathyroidism, 2 = Non-PTH hypercalcemia, 3 = Secondary hyperparathyroidism, 4 = Hypoparathyroidism.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Total Calcium (mg/dL) = 9.5, Albumin (g/dL) = 4, PTH (pg/mL) = 40, 25-OH Vitamin D (ng/mL) = 35 = 4 input(s) provided
Calculate Corrected Calcium
Corrected Calcium = totalCalcium + 0.8 * (4.0 - albumin)
9.5 = 9.5
Calculate Est. Ionized Ca
Est. Ionized Ca = totalCalcium / 2
4.75 = 4.75
Calculate Calcium Status
1 = 1