An elevated calcium level on a routine panel, often 10.6 or 10.8 mg/dL in someone who feels fine, needs two things: a repeat test to confirm it and a parathyroid hormone (PTH) test to find the cause. The two leading causes, an overactive parathyroid gland and cancer, are handled very differently, and that one hormone separates them.
For what calcium does and the full normal range, see the parent page on total calcium. This page covers the high side only.
Where an example calcium of 10.8 mg/dL fallsmg/dL
Is your calcium really high? Check albumin and repeat it
About 40% of the calcium in blood is bound to proteins, mostly albumin, the main blood protein, and roughly half is free, or ionized, which is the form the body uses 2. A standard panel measures total calcium, so albumin moves the result. Dehydration concentrates albumin and pushes total calcium up; a low albumin, common in illness or liver disease, can hide a high calcium. A tight tourniquet held for a long time during the blood draw, or a calcium supplement taken that morning, can also nudge a single result over the line.
Doctors adjust for albumin with corrected calcium: measured calcium plus 0.8 times (4.0 minus albumin in g/dL), the mg/dL form of an adjustment published by Payne and colleagues in 1973 5. When albumin is far from normal, or in kidney disease or critical illness where the formula is less reliable, an ionized calcium test measures the free calcium directly.
CalculatorCorrected calcium calculatorEnter your total calcium and albumin to see your calcium adjusted for protein.Work it out For a mild result, the usual next step is a routine appointment to ask for a repeat calcium, albumin and PTH drawn together, typically within 2 to 4 weeks, skipping calcium and vitamin D supplements the morning of the test.
How high is too high? Mild, moderate and severe
Hypercalcemia is graded by how far total (or corrected) calcium sits above the range 2 1. The grade decides how fast testing and treatment need to happen.
| Grade | mg/dL | mmol/L | What it usually means |
|---|---|---|---|
| Mild | Upper limit to under 12 | Upper limit to under 3.0 | Usually no symptoms. Doctors typically repeat the test and check PTH within weeks. |
| Moderate | 12 to 14 | 3.0 to 3.5 | Often thirst, constipation, tiredness. Usually worked up within days; the same day if symptoms are significant or calcium is rising quickly. |
| Severe | Above 14 | Above 3.5 | A medical emergency even without symptoms. Hospital treatment. |
Most high results fall in the mild band. A calcium of 10.3 or 10.4 mg/dL is borderline on many reports and may settle on a repeat, while a result of 10.2 sits at the top of the usual range. A calcium of 10.5 to 10.7 mg/dL is mildly high; it is rarely dangerous in the short term, and a calcium that stays in that band on repeat testing still deserves a PTH test.
Symptoms of high calcium
Mild high calcium usually causes no symptoms at all. As calcium climbs, the kidneys lose some ability to concentrate urine, so people pee more and feel thirsty 2. Other common symptoms of high calcium are constipation, nausea, loss of appetite, fatigue, low mood, poor concentration, bone aches and kidney stones. At higher levels calcium changes the heart's electrical rhythm (a shorter QT interval on an ECG, the heart tracing) and can cause an irregular heartbeat 2.
Vague symptoms such as tiredness and low mood are common in people with normal calcium too, so a mildly high calcium does not explain them on its own. Thirst, frequent urination and constipation that started together are more suggestive.
What causes high calcium in the blood
A high calcium in a blood test means calcium is entering the blood from bone, gut or kidney faster than the body can clear it, and doctors sort the causes by PTH, the hormone the four parathyroid glands release to raise calcium. If calcium is high and PTH is high or inappropriately normal, the parathyroid glands are driving it. If PTH is suppressed (low or low-normal), the glands have switched off correctly and something else is pushing calcium up 1. **A normal PTH is not reassuring when calcium is high: it usually points to an overactive parathyroid gland 1.**
| PTH result | Cause | How common, and who |
|---|---|---|
| High or normal | Primary hyperparathyroidism (one overactive gland, usually a benign adenoma) | The most common cause in outpatients; more common in women, most often after menopause 1 |
| High or normal | Lithium | Long-term use resets the glands' calcium set point 1 |
| High or normal | Familial hypocalciuric hypercalcemia (FHH) | Inherited and usually harmless; surgery does not help 3 |
| Suppressed | Cancer (via PTH-related peptide, bone spread or myeloma) | The most common cause in hospital; usually in someone already known to have cancer 1 4 |
| Suppressed | Too much vitamin D | Usually very high-dose supplements |
| Suppressed | Sarcoidosis and other diseases that form clumps of immune cells (granulomas) | Immune cells make active vitamin D outside the kidney's control |
| Suppressed | Calcium-alkali (milk-alkali) syndrome | Calcium carbonate supplements or antacids in large amounts |
| Either | Thiazide diuretics | Often unmask an underlying hyperparathyroidism |
| Suppressed | Overactive thyroid, adrenal insufficiency, long immobilisation, excess vitamin A | Less common |
Stewart's review estimated that 20 to 30% of people with cancer develop high calcium at some point, mostly in advanced disease, and that in about 80% of those cases the tumour releases PTH-related peptide (PTHrP), a protein that mimics PTH 4; more recent population studies find lower rates. A first high calcium in someone who feels well and has no known cancer is far more often hyperparathyroidism. Calcium that rises quickly, together with weight loss, night sweats, new bone pain or a cough that will not settle, needs prompt review.
The tests that find the cause, in order
- 1Repeat calcium with albuminConfirms the result is real, ideally fasting, well hydrated and without a calcium supplement that morning. Corrected or ionized calcium settles borderline results.
- 2PTH, measured with the repeat calciumPTH decides which branch of tests follows, so it must be read beside a same-day calcium.
- 3If PTH is high or normalA 24-hour urine calcium checks for FHH: in FHH the kidneys hold on to calcium, so very little shows up in urine 3. Vitamin D, creatinine and eGFR (an estimate of how well the kidneys filter), and a bone density (DEXA) scan follow.
- 4If PTH is suppressedPTHrP, 25-hydroxy and 1,25-dihydroxy vitamin D, protein electrophoresis (a blood test that looks for the abnormal antibody made in myeloma, a bone marrow cancer), phosphate and alkaline phosphatase (ALP), plus imaging guided by symptoms.
The markers that sort out high calcium
Could supplements or medicines be raising your calcium?
Calcium carbonate, whether taken as a supplement or chewed as an antacid for heartburn, can cause calcium-alkali syndrome when intake is high, and it is an increasingly recognised cause of high calcium in people admitted to hospital. Vitamin D raises calcium only at very high blood levels, far above the usual range, almost always from very high-dose products. Thiazide water pills, lithium and high-dose vitamin A can also raise calcium.
Supplements that can push calcium up
Treatment and living with a high calcium
Treatment follows the cause. Mild primary hyperparathyroidism is often watched with yearly calcium and kidney tests and a bone density scan every one to two years, a choice made with the treating specialist. The Fifth International Workshop guidelines recommend surgery when calcium is more than 1 mg/dL (0.25 mmol/L) above the upper limit, with osteoporosis or a vertebral fracture, an eGFR below 60, kidney stones or high urine calcium, or age under 50 3. When a single adenoma is the cause, removing it cures most people 3.
Staying well hydrated helps keep a mildly high calcium from creeping up, and a stomach bug or heat wave that causes dehydration can push it higher. If you have heart failure or kidney disease and have been told to limit fluids, ask your doctor how much to drink. Severe high calcium is treated in hospital with intravenous fluids and medicines that slow calcium release from bone. Left untreated for years, a high calcium raises the risk of kidney stones, bone loss and chronic kidney disease; if your creatinine is also flagged, see high creatinine, and the bone markers guide covers how bone health is tracked.
Free, no accountRead your blood testCalcium makes more sense beside albumin, creatinine and vitamin D. Put your whole panel through the free reader.Read my results
Citations
- Minisola S, Pepe J, Piemonte S, Cipriani C. The diagnosis and management of hypercalcaemia. BMJ 2015;350:h2723
- Sadiq NM, Naganathan S, Badireddy M. Hypercalcemia. StatPearls, NCBI Bookshelf (2023)
- Bilezikian JP et al. Evaluation and management of primary hyperparathyroidism: summary statement and guidelines from the Fifth International Workshop. J Bone Miner Res 2022;37(11):2293-2314
- Stewart AF. Hypercalcemia associated with cancer. N Engl J Med 2005;352:373-379
- Payne RB et al. Interpretation of serum calcium in patients with abnormal serum proteins. BMJ 1973;4:643-646
- MedlinePlus. Calcium blood test. US National Library of Medicine
Educational context only, not medical advice or a diagnosis. Always discuss your results with a clinician.
