Corrected Calcium Calculator
What is Corrected Calcium Calculator
The corrected calcium calculator adjusts a total serum calcium for the patient's albumin level. Because roughly half of blood calcium is bound to albumin, a low albumin drops the total measurement even when the active ionised calcium is normal. Using the Payne correction, it adds 0.8 mg/dL for every 1 g/dL that albumin sits below 4.0, and reports the result in both mg/dL and mmol/L.
How to use
- Enter the measured total calcium and pick its unit, mg/dL or mmol/L.
- Enter the serum albumin and pick its unit, g/dL or g/L.
- Read the corrected calcium in mg/dL, with the mmol/L value below.
- Check the badge to see if the corrected value is low, normal or high.
When to use it
A total calcium looks low but the patient has a low albumin, and you want to know if the calcium is truly low? Enter a calcium of 8.0 mg/dL with an albumin of 2.0 g/dL and the corrected value comes out at 9.6 mg/dL, comfortably normal. It saves you chasing a hypocalcaemia that is really just hypoalbuminaemia, or spotting a genuinely low calcium hidden by a normal-looking total.
Frequently asked questions
Which formula does this use?
It uses the Payne correction: corrected calcium equals measured calcium plus 0.8 mg/dL for every 1 g/dL that albumin is below 4.0 g/dL. It is the most widely taught bedside correction.
When is corrected calcium unreliable?
The correction is only an estimate. In acid-base disturbances, critical illness or marked protein abnormalities it can be inaccurate, and a directly measured ionised calcium is the better test in those settings.
What counts as a normal corrected calcium?
Most labs use a total calcium range of about 8.5 to 10.5 mg/dL (2.1 to 2.6 mmol/L). This tool flags the corrected value against that band, but always confirm with your own laboratory range.
Can I share this tool with my inputs pre-filled?
Yes. The URL updates automatically as you type. Copy it from the address bar or use the Copy link button, and anyone who opens the link will see your exact inputs ready to go.
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