The measurement of plasma calcium is useful whenever the suspected disorder of calcium metabolism, whether from bone – primary storage location – or bowel, kidney or regulating hormones.


In plasma, calcium exists in several forms:

– Calcium not ultra-filterable bound to plasma protein: 45%;

– Ultra-filterable calcium, divided into:

  – Ionized calcium, physiologically active 50%

  – Bound calcium to citrate, phosphate and bicarbonate: 5%.

Parathyroid hormone is hypercalcémiante and prevents bone mineralization.

Calcitonin is hypocalcémiante and promotes calcium deposition on the bone.

Vitamin D is hypercalcémiante   and promotes bone deposition of calcium.


Sampling 5 mL venous blood lithium heparin, away from a meal.

The patient must lie down.

Dosing is by spectrometry.


The usual values are between 90 and 105 mg / L, 2.2 to 2.6 mmol / L.

However, these results should take into account the serum protein: a higher rate increases in serum calcium;conversely, a lower rate decreases.

There is talk of hypercalcemia to a rate higher than 105 mg / L.

if it is observed:

– Bone metastases;

– Primary hyperparathyroidism;

– Sarcoidosis.

There is talk of hypocalcemia for a rate lower than 90 mg / L.

if it is observed:

– Hypoparathyroidism after surgery or primary;

– Vitamin D deficiency:

– Contributed by deficiency

– By absorption disorder,

– By vitamin D deficiency transformation active metabolite.

If hypocalcemia is confirmed, should be measured creatinine and phosphate:

– If hyperphosphatemia is observed, it is:

  – renal failure,

  – Hypoparathyroidism;

– If, however, there hypophosphatemia is osteomalacia.



Practical advice:

Pregnancy, postpartum, birth control pills are down 20% in serum calcium.

Before symptoms of tetany, the review has no diagnostic value.


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