# What is corrected calcium?

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.

- Page: https://www.acalculator.org/health/corrected-calcium-score-calculator
- JSON spec: https://www.acalculator.org/health/corrected-calcium-score-calculator.json
- Version: cdcc703f2345

## Default answer

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.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| calcium | Total calcium | Total serum calcium from the blood test. |
| alb | Albumin | Serum albumin from the same blood test. |
| normalAlb | Normal albumin | The albumin level the correction assumes is normal, usually 4.0 g/dL (40 g/L). |
| corrected | Corrected calcium | Total calcium adjusted to a normal albumin level. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| total | Total calcium | Total serum calcium from the blood test. |
| albumin | Albumin | Serum albumin from the same blood test. |
| normalAlbumin | Normal albumin | The albumin level the correction assumes is normal, usually 4.0 g/dL (40 g/L). |
| corrected | Corrected calcium | Total calcium adjusted to a normal albumin level. |
| correctedMmol | Corrected calcium (mmol/L) | The corrected calcium in millimoles per litre: g/L ÷ 40.078 g/mol × 1,000. |

## Method

corrected calcium (mg/dL) = total calcium (mg/dL) + 0.8 × (normal albumin (g/dL) − albumin (g/dL))

## Assumptions

- 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

1. calcium = 0.095, alb = 40, normalAlb = 40 gives corrected = 0.095. 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.
2. calcium = 0.076, alb = 20, normalAlb = 40 gives corrected = 0.092. 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.
3. calcium = 0.080156, alb = 25, normalAlb = 40 gives corrected = 0.092156, correctedMmol = 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.
4. calcium = 0.08, corrected = 0.09, normalAlb = 40 gives alb = 27.5. 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.

## FAQ

### 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.

## Sources

- Merck Manual Professional Version, Hypocalcemia: measured total serum calcium changes by about 0.8 mg/dL (0.2 mmol/L) for every 1 g/dL change in albumin. https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/electrolyte-disorders/hypocalcemia
- Merck Manual Professional Version, Overview of Disorders of Calcium Concentration: normal total serum calcium 8.8 to 10.4 mg/dL (2.20 to 2.60 mmol/L). https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/electrolyte-disorders/overview-of-disorders-of-calcium-concentration
- 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
- IUPAC CIAAW, abridged standard atomic weights (2021): calcium 40.078. https://ciaaw.org/abridged-atomic-weights.htm