CalculatorsKidneys and electrolytesCorrected calcium calculator
Corrected calcium calculator
Adjust a total calcium for your albumin, and see the working with your own numbers.
9.2mg/dL
In the usual range
About 8.5 to 10.5 mg/dL is the usual range. Labs differ a little.
- In SI units
- 2.31 mmol/L
- Measured calcium
- 8.6 mg/dL+0.6 after correcting
See the working
Corrected Ca = total Ca + 0.8 × (4.0 − albumin)8.6 + 0.8 × (4.0 − 3.2) = 9.24 mg/dLThe correction is an estimate. If it matters, an ionized calcium test is the real answer.
Why calcium needs correcting
About half the calcium in your blood is bound to protein, mostly albumin. If your albumin is low, your total calcium reads low even when the active, free calcium is fine. The Payne formula adds 0.8 mg/dL for each 1 g/dL that albumin falls under 4.
So someone with a low-looking calcium and a low albumin may have nothing wrong with their calcium at all.
When to skip the formula
The correction is an estimate, and it's weakest when someone is seriously ill, or has advanced kidney disease. If the answer matters, ionized calcium measures the active form directly, and it's the better test.
Questions
What's the formula?
Corrected calcium = total calcium + 0.8 × (4.0 − albumin), in mg/dL and g/dL.
What's a normal corrected calcium?
About 8.5 to 10.5 mg/dL (2.12 to 2.62 mmol/L). Labs differ a little, so check your report.
What should I do if it's high?
Raise it with your doctor, who may repeat it and check parathyroid hormone. Very high levels, or symptoms like confusion or palpitations, need attention the same day.
Does vitamin D affect it?
Yes, among other things. Vitamin D helps you absorb calcium, and parathyroid hormone manages the level.
Sources
- Payne RB et al. Interpretation of serum calcium in patients with abnormal serum proteins. BMJ, 1973.
Written by LifeFrom from the sources above, and not yet reviewed by a clinician. An estimate for your own understanding: it doesn't diagnose or treat anything, and it doesn't replace your doctor.
