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Calcium blood test

Total calcium

In short

A typical adult calcium result is 8.6 to 10.2 mg/dL. A small rise is often rechecked, since being low on fluids can nudge it up. If calcium stays high, the most common reason is an overactive parathyroid gland. Always read your result against the range printed on your own report.

A mineral that builds bones and keeps nerves and muscles working.

Four small glands in the neck, the parathyroid glands, keep blood calcium in a tight band. About 40% of it is carried by proteins, mainly albumin, so low albumin makes total calcium look low. That is why doctors read calcium together with albumin, and sometimes measure the free (ionized) part.

Is my Calcium high or low?

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Typical range

ForRangeUnit
Adults8.6–10.2mg/dL
Adults2.15–2.54mmol/L

Typical ranges for adults. Labs differ a little, so the range printed next to your result is the one to go by.

If your Calcium is high

A small rise is often rechecked, since being low on fluids can nudge it up. If calcium stays high, the most common reason is an overactive parathyroid gland.

Common reasons

  • Being low on fluids (dehydration) when the blood was drawn
  • Large amounts of calcium or vitamin D supplements, or antacids with calcium
  • An overactive parathyroid gland, usually from a small non-cancerous growth
  • Some water pills (diuretics) and some mood-stabilizing medicines
  • Long bed rest or weeks without moving much
  • An overactive thyroid gland
  • Less often: some cancers, including cancer that has spread to bone

If your Calcium is low

A low total calcium often reflects low albumin, the protein that carries much of it, rather than truly low calcium. If albumin is in range, doctors look at vitamin D, magnesium, the kidneys and the parathyroid glands.

Common reasons

  • Low albumin, which lowers total calcium but not the active part
  • Low vitamin D
  • Low magnesium, which the parathyroid glands need to work properly
  • Long-term kidney disease
  • Some medicines, including some water pills and some bone-strengthening medicines
  • Past surgery on the thyroid or parathyroid glands
  • Less often: an underactive parathyroid gland or an inflamed pancreas

What can throw it off

Being low on fluids, or the arm band left on too long, can push calcium up a little.

When it can’t wait

A Calcium of 13 mg/dL or more, or 6 mg/dL or less, usually needs a doctor's attention the same day. Call your doctor’s office, or their after-hours line. If you feel very unwell, call your local emergency number.

Questions to take to your appointment

  1. 1Does my albumin explain this result?
  2. 2Should my parathyroid hormone or vitamin D be checked?
  3. 3Could my supplements or medicines play a part?

Read together with

Doctors rarely read Calcium alone. These usually sit next to it.

Quick answers

What is the calcium blood test?

Calcium: A mineral that builds bones and keeps nerves and muscles working. Four small glands in the neck, the parathyroid glands, keep blood calcium in a tight band. About 40% of it is carried by proteins, mainly albumin, so low albumin makes total calcium look low. That is why doctors read calcium together with albumin, and sometimes measure the free (ionized) part.

What is a normal calcium level?

For most adults, calcium is typically 8.6 to 10.2 mg/dL. Some countries print it in mmol/L, so check the unit first. Labs differ a little, so the range printed next to your result is the one to go by.

What does a high calcium mean?

A small rise is often rechecked, since being low on fluids can nudge it up. If calcium stays high, the most common reason is an overactive parathyroid gland. Common reasons include being low on fluids (dehydration) when the blood was drawn; large amounts of calcium or vitamin D supplements, or antacids with calcium; an overactive parathyroid gland, usually from a small non-cancerous growth; and some water pills (diuretics) and some mood-stabilizing medicines. A doctor reads it together with your other results and how you feel.

What does a low calcium mean?

A low total calcium often reflects low albumin, the protein that carries much of it, rather than truly low calcium. If albumin is in range, doctors look at vitamin D, magnesium, the kidneys and the parathyroid glands. Common reasons include low albumin, which lowers total calcium but not the active part; low vitamin D; low magnesium, which the parathyroid glands need to work properly; and long-term kidney disease.

What can affect my calcium result?

Being low on fluids, or the arm band left on too long, can push calcium up a little.

When is my calcium result urgent?

A calcium result of 13 mg/dL or more, or 6 mg/dL or less usually needs a doctor's attention the same day. Call your doctor's office or their after-hours line. If you feel very unwell, call your local emergency number.

What should I ask my doctor about my calcium?

Questions worth taking to the appointment: Does my albumin explain this result? Should my parathyroid hormone or vitamin D be checked? Could my supplements or medicines play a part?

What this page can’t do

It reads each number on its own.

Doctors read results together — ALT with AST, ferritin with hemoglobin, TSH with free T4. A pattern says more than any single flag.

It doesn't know you.

Your age, your medicines, how you feel and your last result all change what a number means.

It doesn't remember.

Close this page and your results are gone. That's on purpose: nothing was ever sent to us.

We also make Vita: Health Coach, an app for those parts. It reads your whole report with your medicines and history in mind, answers follow-up questions in plain words, and keeps your reports in one place — for you and for the people you look after.

Vita: Health Coach on the App Store

Sources

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