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Calcium
A mineral of bones, nerves, muscles, and heart, tightly controlled by the parathyroid glands.
Other names: Total calcium, serum calciumSection: Blood chemistry
Updated: August 29, 2026·MedProtect editorial team Reference information — not a diagnosis or a prescription
In shortNormal values range from 8.8–10.3 mg/dL (2.20–2.58 mmol/L). Both high and low values usually trace back to the parathyroid glands, vitamin D, kidneys, or bones.
Reference ranges
Group
Reference range
Adults
8.8–10.3 mg/dL (2.20–2.58 mmol/L)
Normal value ranges vary slightly among laboratories, and some labs use different measurements or test different specimens.
Check your value
Enter the number from your lab report — see how it compares with the typical range. Mind the units shown in the chosen row.
A rough comparison with a typical range, not a diagnosis. Reference ranges vary between laboratories — check the range on your own report and let a clinician interpret the result.
What this marker is
All cells need calcium in order to work. The mineral builds strong bones and teeth, supports heart function, and takes part in muscle contraction, nerve signaling, and blood clotting. Because so much depends on it, the blood level is kept in a narrow corridor, mainly by the parathyroid glands and vitamin D.
The standard test measures total calcium in the blood; a related test measures ionized (free) calcium. Results are reported in milligrams per deciliter (mg/dL); in millimoles per liter (mmol/L) in many countries. Because albumin carries part of the blood calcium, a low albumin can make total calcium read low — one reason the two tests are often read together.
Providers order the test for signs of bone disease, certain cancers, chronic kidney or liver disease, parathyroid disorders, poor intestinal nutrient absorption, high vitamin D levels, or an overactive thyroid — and after long periods of bed rest.
Blood is drawn from a vein. Diet and certain medicines can shift calcium levels, so the provider needs to know what you take; the result is then read against the symptoms and the other tests rather than alone.
When it is high
HyperparathyroidismWhen the parathyroid glands make too much of their hormone, calcium is pulled into the blood. This is a leading cause of a high result.
Cancer involving boneMultiple myeloma, T-cell lymphoma, certain other cancers, and tumors that have spread to bone release calcium; some tumors produce a parathyroid-hormone-like substance.
Too much calcium or vitamin DLong-term excess intake of calcium or vitamin D raises the blood level.
Overactive thyroidHyperthyroidism — or too much thyroid hormone medicine — can push calcium up.
Granuloma diseases and Paget diseaseTuberculosis, certain fungal and mycobacterial infections, sarcoidosis, and Paget disease of bone all appear on the list.
Medicines and bed restLithium, tamoxifen, and thiazides can raise calcium, and long periods of bed rest release it from bone.
When it is low
HypoparathyroidismToo little parathyroid hormone lets calcium fall — the mirror image of the most common high-calcium cause.
Vitamin D or magnesium deficiencyVitamin D drives calcium absorption, and magnesium is needed for the parathyroid system; shortages of either lower calcium.
Kidney insufficiency or failureDamaged kidneys disturb the calcium–vitamin D balance.
Low albumin, liver disease, pancreatitisA low blood albumin lowers total calcium readings; liver disease and pancreatitis are also listed causes.
Intestinal malabsorptionDisorders that impair nutrient absorption cut calcium intake at the source.
What can skew the result
These factors can shift the value without any disease — worth considering before a retest:
DietCertain medicines (lithium, tamoxifen, thiazides)Albumin level (part of calcium travels bound to it)Vitamin D status
How to prepare
No special preparation is usually needed. Tell your provider about the medicines and supplements you take — including vitamin D and calcium — because diet and certain medicines affect the level.
When a retest makes sense
An abnormal total calcium is typically rechecked and interpreted together with albumin; when needed, the provider adds the ionized calcium test or parathyroid hormone measurement to find the cause.
Who usually reviews this result
A result outside the reference range is usually reviewed by: your GP or primary care doctor; an endocrinologist if a parathyroid problem is suspected. Bring your lab report and any previous results to the appointment.
Names used on lab reports
Your report may use any of these names: CalciumTotal calciumSerum calciumCaIonized calcium
Units and conversion
Measured in: mg/dL
mg/dL=mmol/L
mg/dL × 0.25 = mmol/L. Example: 9.6 mg/dL = 2.40 mmol/L. Results are rounded to 2 decimal places.
Several markers on your report?
See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.
What is the difference between total and ionized calcium?
Total calcium measures all calcium in the blood, including the share bound to albumin; ionized calcium measures the free, active fraction. The total test is the standard one; the ionized test answers specific questions.
Can low albumin fake a low calcium?
Yes. Because part of the calcium travels bound to albumin, a low albumin level can make total calcium read low. That is why calcium and albumin are often read together.
Do calcium supplements affect the test?
They can. Long-term excess of calcium or vitamin D is a listed cause of high values, so tell your provider about the supplements you take.
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