High Blood Calcium: Symptoms and What a High Result Means

What a high calcium result means

Calcium is tightly controlled by parathyroid hormone (PTH), made by four tiny glands in the neck, and by vitamin D. Together they move calcium between bones, gut and kidneys to keep blood levels in a narrow range.

About 40 to 45% of calcium in blood is bound to the protein albumin. If albumin is low or high, the lab or doctor calculates a "corrected" calcium, or measures ionized (free) calcium directly. A single high result can be falsely raised by dehydration or a tight tourniquet, so it is usually repeated.

Symptoms of high calcium

Doctors remember them as "stones, bones, groans, thrones and psychiatric overtones":

• Stones: kidney stones, causing flank pain and blood in the urine
• Bones: bone pain, osteoporosis and fractures, mainly from long-standing parathyroid disease
• Groans: constipation, nausea, loss of appetite, abdominal pain, and occasionally pancreatitis or ulcers
• Thrones: excessive thirst and frequent urination, because calcium stops the kidneys concentrating urine, which leads to dehydration
• Psychiatric overtones: tiredness, low mood, poor concentration, memory problems, and in severe cases confusion and drowsiness

Other effects include muscle weakness, high blood pressure and heart rhythm problems.

How you feel depends on how high the calcium is and how fast it rose. A slow rise over years, typical of parathyroid disease, often causes vague symptoms people put down to stress or aging. A fast rise, typical of cancer, causes more obvious symptoms.

Main causes

Primary hyperparathyroidism

This is the most common cause found in otherwise well people. Usually a single benign parathyroid adenoma makes too much PTH. It is most common in women after menopause. Calcium is usually only mildly raised and PTH is high or inappropriately normal. See hyperparathyroidism.

Cancer

Cancer is the most common cause in people admitted to hospital with high calcium. Tumors may release a PTH-like hormone (lung, breast, kidney and head and neck cancers) or spread to bone. Multiple myeloma is a common cause. Calcium tends to be higher and rise faster, and PTH is low.

Other causes

• Medicines: thiazide diuretics, lithium, too much vitamin D or calcium supplements, vitamin A
• Granulomatous diseases: sarcoidosis and tuberculosis make extra active vitamin D
• Dehydration, which concentrates calcium
• Prolonged immobility, especially in young people or with Paget's disease
• Overactive thyroid and adrenal insufficiency
• Familial hypocalciuric hypercalcemia: an inherited, harmless condition that mimics hyperparathyroidism

What happens next

After a high result, a doctor will usually:

1. Repeat the calcium with albumin, or measure ionized calcium.
2. Check PTH. This single test separates parathyroid-driven causes (PTH high or normal) from others (PTH low).
3. Check kidney function, phosphate, vitamin D and magnesium.
4. Review medicines and supplements.
5. Look for cancer if PTH is low: examination, chest X-ray, blood and urine protein tests for myeloma, and other scans.
6. Measure urine calcium to rule out the inherited condition.
7. Bone density scan and kidney imaging if hyperparathyroidism is confirmed.

What you can do now

• Drink plenty of water unless a doctor has told you to restrict fluids. Aim for pale yellow urine.
• Stop calcium and vitamin D supplements until you have discussed them with your doctor.
• Do not cut calcium out of your diet completely unless advised. Low dietary calcium can make PTH rise further.
• Bring a list of all medicines and supplements to your appointment.
• Stay active, because immobility releases calcium from bone.

Treatment depends on the cause and level. Mild parathyroid-related hypercalcemia may be monitored or cured with surgery. Severe hypercalcemia needs hospital treatment with IV fluids and medicines. For full details, see the hypercalcemia condition guide.

Frequently asked questions

What are the symptoms of high calcium levels?

Mild high calcium often causes no symptoms. Higher levels cause thirst, frequent urination, constipation, nausea, tiredness, muscle weakness, aches, low mood and poor concentration. Very high levels can cause confusion, drowsiness and heart rhythm problems.

What is the most common cause of high calcium?

In people who are otherwise well, the most common cause is primary hyperparathyroidism, usually from a benign growth in one parathyroid gland. In hospital patients, cancer is the most common cause. Together they account for about 90% of cases.

Is a calcium level of 10.6 high?

It is just above the usual upper limit of about 10.5 mg/dL, so it is mildly high. It should be repeated with albumin, and parathyroid hormone should be checked. Mild results often reflect parathyroid disease, which is not an emergency but needs follow-up.

Can dehydration cause high calcium?

Yes. Dehydration concentrates the blood and reduces calcium removal by the kidneys, which can raise the level. High calcium also causes dehydration by increasing urination, creating a cycle. If calcium stays high after rehydration, another cause should be sought.

Does high calcium mean cancer?

Not usually, especially when it is mild and you feel well. Most mild cases are due to an overactive parathyroid gland. Cancer becomes more likely when calcium is high and rising quickly, PTH is low, or there are symptoms such as weight loss.