What is corrected calcium?
Calculate corrected calcium levels for patients with abnormal protein levels. Medical diagnostic tool.
- Corrected calcium
- 9.5 mg/dL
With albumin 4 g/dL, a total calcium of 9.5 mg/dL corrects to 9.5 mg/dL.
Normal
- Low
- Normal
- High
- Corrected calcium (mmol/L)
- 2.37
Corrected calcium: 9.5 mg/dL. With albumin 4 g/dL, a total calcium of 9.5 mg/dL corrects to 9.5 mg/dL.
This calculator gives general information only. It is not medical advice and does not replace a doctor or other health care provider. Talk with a professional about your results. Terms of use
How to calculate
Adjusts total serum calcium for a low or high albumin: corrected calcium = total calcium + 0.8 × (normal albumin − albumin), in mg/dL and g/dL, or any other unit.
Example with the default inputs (Total calcium 9.5 mg/dL, Albumin 4 g/dL, Normal albumin 4 g/dL): With albumin 4 g/dL, a total calcium of 9.5 mg/dL corrects to 9.5 mg/dL.
Formula: corrected calcium (mg/dL) = total calcium (mg/dL) + 0.8 × (normal albumin (g/dL) − albumin (g/dL))
- The factor is 0.8 mg/dL of calcium per 1 g/dL of albumin (Merck Manual). Other units are converted to mg/dL and g/dL first; mmol/L uses the calcium molar mass 40.078 g/mol.
- Normal albumin defaults to 4.0 g/dL (40 g/L), the value in Payne et al. (1973).
- The normal range shown is the Merck Manual adult total serum calcium range, 8.8 to 10.4 mg/dL (2.20 to 2.60 mmol/L). Labs set their own ranges.
Worked examples
Each example is checked against the calculator on every build.
- Total calcium 9.5 mg/dL, Albumin 4 g/dL, Normal albumin 4 g/dL gives Corrected calcium 9.5 mg/dL.Source: Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4(5893):643-646. https://doi.org/10.1136/bmj.4.5893.643
- Total calcium 7.6 mg/dL, Albumin 2 g/dL, Normal albumin 4 g/dL gives Corrected calcium 9.2 mg/dL.Source: Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4(5893):643-646. https://doi.org/10.1136/bmj.4.5893.643
- Total calcium 8.016 mg/dL, Albumin 2.5 g/dL, Normal albumin 4 g/dL gives Corrected calcium 9.22 mg/dL, Corrected calcium (mmol/L) 2.299416.Source: Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4(5893):643-646. https://doi.org/10.1136/bmj.4.5893.643
- Total calcium 8 mg/dL, Corrected calcium 9 mg/dL, Normal albumin 4 g/dL gives Albumin 2.75 g/dL.Source: Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4(5893):643-646. https://doi.org/10.1136/bmj.4.5893.643
How corrected calcium is worked out
Corrected calcium (mg/dL) = total calcium (mg/dL) + 0.8 × (normal albumin (g/dL) − albumin (g/dL))
- The factor 0.8 is the Merck Manual rule: total calcium falls about 0.8 mg/dL for every 1 g/dL that albumin falls.
- Normal albumin is 4.0 g/dL (40 g/L) unless you change it. Payne et al. (1973), who first adjusted calcium for albumin, used 4.0 g/dL.
- Other units are converted first: 1 g/L = 0.1 g/dL, and for calcium 1 mmol/L = 40.078 mg/L = 4.0078 mg/dL (molar mass 40.078 g/mol). You can mix units, for example calcium in mmol/L with albumin in g/dL.
- In SI units the same rule is corrected (mmol/L) = total (mmol/L) + 0.019956 × (normal albumin (g/L) − albumin (g/L)). The common shortcut 0.02 mmol/L per g/L gives almost the same answer: for albumin 15 g/L below normal, 0.300 against 0.299 mmol/L.
Fill in any three of the four values and the calculator finds the fourth:
- total = corrected − 0.8 × (normal albumin − albumin)
- albumin = normal albumin − (corrected − total) ÷ 0.8
- normal albumin = albumin + (corrected − total) ÷ 0.8
Every value must be above 0. A solved value at or below 0 has no answer.
Normal range
The result panel marks the value with the Merck Manual adult range for total serum calcium: low below 8.8 mg/dL, normal 8.8 to 10.4 mg/dL (both ends included), high above 10.4 mg/dL. Your lab's range may differ.
Assumptions
- The rule is an estimate. In kidney disease, liver disease, critical illness, or myeloma, ionized calcium measured directly is better.
- Values are not rounded between steps.
Worked examples by hand
9.5 mg/dL with albumin 4.0 g/dL. 9.5 + 0.8 × (4.0 − 4.0) = 9.5 mg/dL, normal.
7.6 mg/dL with albumin 2.0 g/dL. 7.6 + 0.8 × (4.0 − 2.0) = 7.6 + 1.6 = 9.2 mg/dL, normal. This matches the Merck Manual example: an albumin of 2.0 g/dL lowers calcium by about 1.6 mg/dL.
2.00 mmol/L with albumin 25 g/L. 2.00 mmol/L = 2.00 × 4.0078 = 8.0156 mg/dL, and 25 g/L = 2.5 g/dL. 8.0156 + 0.8 × (4.0 − 2.5) = 8.0156 + 1.2 = 9.2156 mg/dL = 9.2156 ÷ 4.0078 = 2.2994 mmol/L.
Which albumin gives a corrected 9.0 from a total of 8.0? albumin = 4.0 − (9.0 − 8.0) ÷ 0.8 = 4.0 − 1.25 = 2.75 g/dL (27.5 g/L).
Other questions people ask
What is corrected calcium?
Corrected calcium is an estimation of your calcium level that accounts for your albumin (protein) levels. Since calcium binds to albumin in the blood, low albumin can make your total calcium appear lower than it actually is. This calculation estimates what your calcium would be if your albumin were normal.
When should I use this calculator?
This calculator is useful when you have abnormal albumin levels and want to estimate your true calcium status. However, it's important to note that this is an estimation tool and should not replace professional medical advice or direct measurement of ionized calcium in complex medical situations.
What are normal calcium levels?
The Merck Manual gives a normal total serum calcium of 8.8 to 10.4 mg/dL (2.20 to 2.60 mmol/L) for adults. However, reference ranges vary between laboratories, so always compare your result to the range provided by your specific lab.
What causes high or low calcium levels?
High calcium (hypercalcemia) is most commonly caused by overactive parathyroid glands or certain cancers. Low calcium (hypocalcemia) can result from underactive parathyroid glands, vitamin D deficiency, or kidney disease. Always consult a healthcare provider for proper diagnosis.
Is this calculator accurate for everyone?
No. This calculator uses a standard formula that may not be accurate in patients with advanced kidney disease, liver disease, critical illness, or certain cancers like multiple myeloma. In these cases, direct measurement of ionized calcium is preferred.
What's the difference between mg/dL and mmol/L?
These are different units for measuring concentration. The United States typically uses mg/dL (conventional units), while most other countries use mmol/L (SI units). For calcium, 1 mmol/L is 4.008 mg/dL. Type mmol/L after the number (for example 2.2 mmol/L), or use mg/dL. Albumin can be in g/dL or g/L, in any mix. The result is shown in both mg/dL and mmol/L.