What Is Corrected Calcium?
Corrected calcium (also called adjusted calcium) is a calculation that accounts for the effect of albumin levels on total calcium measurement. Approximately 40–45% of calcium in your blood is bound to the protein albumin. When albumin levels are abnormal (as commonly occurs in liver disease, kidney disease, malnutrition, or inflammation), the total calcium measurement can be misleading — appearing falsely low when albumin is low, or falsely high when albumin is high.
The corrected calcium formula adjusts for this by estimating what the total calcium would be if albumin were at a normal level (typically 40 g/L). This provides a more accurate representation of the physiologically important calcium fraction, making it the standard calcium value reported by most UK laboratories.
The Correction Formula
Corrected calcium = Total calcium + 0.02 × (40 − albumin in g/L)
Example: If total calcium is 2.15 mmol/L and albumin is 30 g/L: Corrected calcium = 2.15 + 0.02 × (40 − 30) = 2.15 + 0.20 = 2.35 mmol/L
Why Is Corrected Calcium Tested?
- Assess calcium status accurately in patients with abnormal albumin levels
- Investigate symptoms of hypercalcaemia: thirst, frequent urination, constipation, confusion, kidney stones
- Investigate symptoms of hypocalcaemia: muscle cramps, tingling, seizures, prolonged QT on ECG
- Monitor parathyroid function — calcium regulation is primarily controlled by PTH and vitamin D
- Evaluate bone health alongside vitamin D and phosphate
- Monitor patients on medications that affect calcium (thiazide diuretics, lithium, bisphosphonates)
- Part of routine health screening and metabolic panels
Normal Ranges
| Measurement | Normal Range |
|---|---|
| Corrected calcium (adults) | 2.20 – 2.60 mmol/L |
| Mild hypercalcaemia | 2.60 – 3.00 mmol/L |
| Moderate hypercalcaemia | 3.00 – 3.40 mmol/L |
| Severe hypercalcaemia | Above 3.40 mmol/L (medical emergency) |
| Hypocalcaemia | Below 2.20 mmol/L |
Causes of High Corrected Calcium (Hypercalcaemia)
- Primary hyperparathyroidism: The most common cause — a benign parathyroid adenoma produces excess PTH
- Cancer: The second most common cause — bone metastases, myeloma, and PTHrP-secreting tumours
- Vitamin D toxicity: Excessive supplementation (usually >10,000 IU/day for months)
- Sarcoidosis and granulomatous diseases: Immune cells convert vitamin D to its active form
- Thiazide diuretics: Reduce calcium excretion by the kidneys
- Lithium: Raises the PTH set-point, causing mild hypercalcaemia
- Thyrotoxicosis: Excess thyroid hormones increase bone resorption
- Immobilisation: Prolonged bed rest causes calcium to leach from bones
- Familial hypocalciuric hypercalcaemia (FHH): Benign genetic variant — calcium is mildly elevated but does not require treatment
Causes of Low Corrected Calcium (Hypocalcaemia)
- Vitamin D deficiency: The most common cause in the UK — inadequate sunlight and dietary intake
- Hypoparathyroidism: Underactive parathyroid glands, often after thyroid surgery
- Chronic kidney disease: Impaired vitamin D activation reduces calcium absorption
- Magnesium deficiency: Severe hypomagnesaemia impairs PTH secretion and action
- Acute pancreatitis: Calcium is consumed in fat saponification
- Malabsorption: Coeliac disease, Crohn's disease, or short bowel syndrome
- Medications: Bisphosphonates, denosumab, calcitonin, or loop diuretics
- Pseudohypoparathyroidism: Genetic resistance to PTH action
How to Maintain Healthy Calcium Levels
- Get adequate dietary calcium: Adults need 700mg/day (UK RNI) — dairy, fortified plant milks, sardines, tofu, kale, and broccoli
- Ensure sufficient vitamin D: Vitamin D is essential for calcium absorption — supplement in winter months
- Exercise regularly: Weight-bearing exercise strengthens bones and supports calcium balance
- Don't over-supplement calcium: Excessive calcium supplements (>1,000mg/day) may increase cardiovascular risk
- Maintain adequate magnesium: Magnesium is required for PTH function and vitamin D activation
- Limit excessive salt and caffeine: Both increase urinary calcium excretion
When Should You Get Tested?
- You experience muscle cramps, tingling, or numbness (possible hypocalcaemia)
- You have persistent thirst, frequent urination, or constipation (possible hypercalcaemia)
- You have been diagnosed with kidney disease, parathyroid problems, or vitamin D deficiency
- You take medications that affect calcium levels
- You have osteoporosis or osteopenia and want to monitor calcium metabolism
- You have had thyroid or parathyroid surgery
Which Lola Health Tests Include Corrected Calcium?
- Peak Insights — includes corrected calcium, vitamin D, and full bone health markers
- Vital Check — includes calcium as part of a comprehensive metabolic panel
- Core Health — essential health screening with calcium
Check Your Calcium Levels
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